2 Advanced Topics Important technical topics for those wishing to gain a finer understand of the craft.
This Advanced Topics e-booklet will cover the following topics: • How Do You Choose a 3rd-Party Flash? • The “Lazy Eye” syndrome • The Basics of Proper Exposure (including some surprising metering behavior!) • Zone Matching and DRO (Skip this if you own an A1 or A2 ☺) • An Incident Light Meter That’s Always With You • Recovering Poorly-Exposed Images and Expanding Apparent Dynamic Range using RAW • High-Speed Sync (HSS) at High Speeds • The Noise about Noise (plus an unintuitive way to reduce it!) • Cold Weather Operation
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Introduction This e-booklet contains topics that are a bit too technical for an introductory book, but tend to be of value for people who are interested in learning the finer points of features of their camera. One thing you’ll note is that, when a specific feature is discussed, I won’t spell out for you how to invoke that feature (like I do in the books). The reason for this is twofold: 1. I’ve written books for many different cameras, and each camera invokes their features differently. 2. Hey, this is an ADVANCED Topics book – it is assumed that you are already familiar with how to invoke features in your camera! (It’s OK if you’re not – it’s easy to look up the feature in the original book and refresh your memory! ☺ ) I plan on doing more of these as time goes by, and so if you have a nagging advanced subject that you don’t find discussed here, drop me an email to
[email protected], and I’ll address the most popular requests in future versions.
v1.5
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Figure 1: There’s a hidden switch on the flash’s hot shoe designed to tell the camera if the accessory flash is mounted on the camera or not. This in turn determines whether ADI (Advanced Distance Integration) can be used in determining flash exposure – if the flash is on the camera, the flash Subject distance is known; if it’s off the camera there’s no way to know. This switch is pressed in when mounted to the camera’s hot shoe, but the little divot in the off-camera flash stand makes sure this switch is not depressed when used off-camera. Now you know.
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How Do You Choose a 3rd Party Flash? I think I have received more emails asking questions about recommending a 3rd party flash than on any other single topic. Of course the problem with writing about it is that there are so many variables – what kind of hot shoe does the flash have? Is it a “Dedicated Minolta/Sony hot shoe”, and if so from what era? (If it was from more than 10 years ago it might not fire on a digital camera.) Is there an autosensor on the flash, or does it rely on the camera to determine exposure? Does the 3rd party flash claim wireless flash compatibility? Can the flash be fired with a PC-Sync cord, and is there a PC-Sync terminal on your camera? With the flash work in HSS mode both on-camera as well as off? No two 3rd party flashes are alike, so it’s impossible to give short and sweet advice for such large questions. Probably the best way to answer this question, then, is to sit back, take a deep breath, and explain some of the history of the flash connectivity and triggering standards that have transpired over the years, and how they were all supposed to work together. (Trust me, this will be worthwhile, for it will make the eventual answers very easy to understand.) Armed with this, and knowledge of the era that your flash was made in, should be extremely helpful in getting your flash and your digital camera to work together (if they can work together at all!). Once upon a time there were cold shoes. Nobody called them that, but that’s what they were -- small brackets mounted onto the camera body onto which you could mount your flashbulb holder. They looked like the image in Figure 2. Once mounted, you would connect the flashbulb holder electronically to the camera
Figure 2: The original flash bracket holder, and the PC-Sync connector on the camera that electrically synchronized the flash with the camera’s shutter.
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via a PC Sync cord into a PC Sync socket (also shown to the right). Inside the camera there was a mechanical switch which briefly “shorted together” the 2 wires of the PC Sync cable when the shutter was actuated. It was a very simple and very effective mechanism, which also worked well when the electronic flash was invented. “Hey, let’s get rid of that annoying PC Sync cable!” one engineer must have said to himself one day in the 1960’s, as he devised what is now known as the “Hot Shoe” (Figure 3). The metal rails on the bracket, coupled with the metal circle in the center, served to provide a replacement for the two wires in the PC Sync cord. Mind you, at this stage the only thing this provided for was to tell the flash when to fire – no other information was exchanged. The flash would always output a fixed amount of light, and it was up to the photographer to calculate the distance of the subject and use the appropriate f/stop to ensure proper illumination. This was often a time-consuming task for each and every shot. In the 1970’s, Thrysistor flash circuitry was developed. AutoThrysistor flashes had a tiny forward-facing sensor in them (Figure 4) that would look at the subject, and when the sensor saw that the subject had enough light it would stop outputting light during the exposure. (At this point “outputting” became a legitimate word. ☺ ) This was a huge leap forward in flash technology, for it meant that the photographer didn’t have to calculate or change the f/stop each time the subject changed distances! (Well, not usually… the amount of
Figure 3: The “hot shoe” combined the mechanical mount with the electrical connector, eliminating the need for that annoying PC Sync cord. The top image is from a Minolta 35 Model 1-A camera (the first known implementation of a hot shoe), and the bottom shows a more modern implementation.
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flash output that could be automatically controlled was so narrow that the photographer would often have to change between 3 ranges involving 3 different f/stops if the distance changed dramatically. So, while not being headache-free, it was still a substantial improvement.) The other good news is that there was no need to modify the hot shoe, which had become very popular by that time. 1980’s: The drawback to the Auto-Thrysistor circuits was that if you had a filter in front of the lens, or if you had used a different f/stop, or if your zoom lens would actually change f/stops as you zoomed from wide to telephoto (a common thing!), then the actual amount Figure 4: Auto-Thrysistor of light that got through to the film would flashes tend to have their own light sensor which change, resulting in your flash pictures faces forward. You tell it most likely being underexposed. To the ISO and f/stop you’re address this problem, in the 1980’s using, and it will camera companies started to move the automatically adjust the flash sensor from the front of the flash to Figure 5: So much for flash’s output if your subject is within a certain inside the camera, reading the light that standards! TTL Flash range. necessitated got reflected off the film plane. This new metering connections system was dubbed “TTL” (“Through The Lens”), and its main additional between the flash and advantage was you could use ANY f/stop, distance, or filter (or camera, and no two combination of filters) and the flash exposure would still be accurate – manufacturers did it the no adjustments by the photographer were ever necessary. And to same way. Above is a hot accommodate this additional communication between the camera and shoe configuration from flash, additional connections were necessary (Figure 5). Here’s where Nikon. Contents of this book Copyright © 2007 Gary L. Friedman. All rights reserved.
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things started to get proprietary, for a TTL flash for Nikon would not work on a Canon or a Minolta. Here’s also where things started to become unreliable, for if the flash was not mounted and secured just perfectly onto the hot shoe, a flash exposure error would almost certainly take place. And so, during their Decade of being Different (1990’s), Minolta decided to re-design the flash hot shoe from the ground up, to address the reliability problems (Figure 6). (“Hey, there’s no interoperability anymore, so it shouldn’t matter!”) This was a good thing from a technical point of view, but it made it very difficult for Minolta-shooting professionals (both of them) to rent 3rd party flash equipment and “radio slaves” because suddenly Minolta was incompatible with everything. Up until this point the mechanism for firing the flash was still the same – there was either a physical switch, relay contact, or switching transistor inside the camera which created a brief “short circuit” the instant the shutter was released, so that even if you used a flash shoe adapter (like the FS-1100, also in Figure 6, designed specifically so that you COULD use older and 3rd party flashes), your flash would still fire. (In the new hot shoe format, the two contacts that are closest to the viewfinder’s eyepiece are the ones that get shorted together to cause the flash to fire.)
Figure 6: Minolta redesigned the hot shoe flash to be more reliable and significantly faster to mount and remove the flash. The FS-1100 hot shoe adapter (right) was also available if you wanted to fire an older flash designed for a conventional hot shoe (but it won’t work on digital bodies).
Then something happened. Sometime after 1995, after the production of the Minolta 700si 35mm SLR camera, an engineer in Japan said, “Hey, let’s make our cameras completely incompatible with every flash ever made!” And so, without fanfare and without changing the physical appearance of the proprietary hot shoe, Minolta’s cameras no longer contained an internal switch that would “short out” and tell a 3rd party flash when to fire.
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Instead, the existing contacts would communicate with their HS and HS(D)-series flashes (like the 5400 HS and 5600 HS(D)) via a serial protocol and issue software commands to fire the flash. Suddenly, 3rd party flashes that used to fire on a 700si via the FS-1100 hot shoe adapter wouldn’t fire at all when mounted on a Maxxum 9 or 7 film camera. (Or on any DSLR since then.) That’s not a tremendous problem, since 3rd party flash manufacturers (most notably Sigma and Metz) have kept up, and designed their flashes with the special Minolta foot and could communicate with the camera through the special Minolta serial protocol. BUT if you have a flash that was made before 1995, even if it was “Minolta Compatible” and had the Minolta hot shoe, it probably won’t fire. And that goes double if you have any 3rd party flash that was designed for the traditional hot shoe.
285 5 or the Sunpak But what if I have an older flash, such as a Vivitar 28 Sunpak 120J that I want to use on my digital camera? The Vivitar 285 and the Sunpak 120J are classic Auto-Thrysistor flashes that have their own light sensor. You tell them the f/stop and the ISO of the film you were using, and they would adjust its output (within certain limits) based on the amount of light that bounced back and hit the sensor. These flashes (and many like them) were designed for a conventional hot shoe, and so you would need the FS1100 adapter just to physically mount the flash to the camera. (The flash won’t fire, though, for reasons mentioned previously.) With such a setup, there’s only one way to get the flash to fire, and that is to hook up a PC Sync cord between the camera and flash. Fortunately, the 285 has the ability to attach to a PC Sync cord, which means you use it with the Konica Minolta 7D, A1, or A2.
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NOTE: In its last years, Minolta did come out with the PCT-100 adapter (Figure 7a) which mounted on the camera’s hot shoe and provided a PC Sync terminal to cameras that didn’t have one built in, such as the 5D and the A100. BUT… using this device completely occupies the hot shoe, and there is no additional hot shoe on top for mounting your 3rd party flash! This device is clearly designed for studio work and not necessarily to help you connect an older flash. rd
What if my 3 party flash uses the old hot shoe and can’t take a PC Sync cord? Then a 3rd party product is what you need: It’s the “Hot Shoe Adapter III” available from Gadget Infinity (http://gadgetinfinity.com/product.php?productid=16548&cat=0) (Figure 7b below). It is designed to look like a Minolta or Sony flash to the camera, and will accept the serial-based “Fire!” software command and then “short out” the hot shoe contact on top for true backward compatibility and NO risk to your camera’s hot shoe electronics. Notice the lack of all those special pins which historically provided flash exposure feedback to the camera – this one will just tell the flash to fire and that’s it! If you ever want to use a radio slave for your studio flashes, or have an AutoThrysistor flash, this is the hot shoe adapter for you! (Special thanks to reader Robert Fowler for pointing this out to me.)
Figure 7 (a and b): The PCT-100 (above) as seen from the bottom and the top. Notice that it only provides a PC Sync cord connector; the top has no hot shoe for an accessory flash to sit upon.. If a plain hot shoe is what you need, then the 3rd party “Hot Shoe Adapter III” is for you (below).
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3rd party flashes that work Okay, enough kludges. By now you’re probably thinking to yourself, “Aren’t there ANY third party flashes that are actually compatible with a Sonolta digital camera and don’t require all these &^%%$# adapters?” The answer is yes, there are two such flashes on the market that I would recommend: the Sigma EF-500 Super DG Super seems to be popular, although word has it that it doesn’t handle High-Speed Sync offcamera properly and doesn’t interoperate wirelessly with Sony or Minolta flashes very well. But there is one 3rd party flash that actually offers an improvement over the Minolta and Sony flashes. It is the Metz 54 MZ-4i and the hot-shoe adapter SCA 3302 M7 (see the following URLs: http://www.bhphotovideo.com/bnh/controller/home?A=ShowProduct&is=REG&Q=&O=&sku=326507 http://www.bhphotovideo.com/c/product/217271REG/Metz_MZ53302_SCA_3302_Dedicated_Module.html This flash has a secondary flash for great results when bouncing the light off the ceiling, and also supports wireless mode. And in addition to working with Minolta’s TTL flash metering (at least in theory – there are field reports of less-than-stellar flash exposure in TTL and ADI modes), it also provides the Auto- Thrysistor flash exposure using the flash’s own built-in light sensor. (Why on earth would that be valuable? Read the next section on Lazy Eye to find out…)
I have an older Minolta HS or XI series flash. Can I use it on my digital digital body? Because the older Minolta flashes didn’t have the native ability to fire a pre-flash, the official answer is “No, those flashes won’t work on newer digital bodies.” The longer, un-official answer is “Yes, they
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will fire but there’s no ability to adjust exposure automatically – the flash will only fire full-power (even though it’s set to Manual output mode). But there’s more to the story… someone in Germany has actually created a tiny microprocessor-based adapter which sits between the camera’s hot shoe and the older flash’s circuitry and allows the older flashes to be used on some digital bodies. It’s not clear from the documentation how they get around the need for a pre-flash, but it looks as if they intend to offer completed circuits for sale in the near future. If you’re good with a soldering iron and aren’t squeamish about taking your flash apart, this just might be of interest to you: www.voitzsch.net/flashconv_en.shtml Note that once you update your flash with this new circuitry, it will no longer work on your Minolta film cameras.
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“Lazy Eye” Have you ever taken a picture of someone, only to discover that, no matter what, their eyes always appear half-closed? This isn’t just a matter of bad luck – the condition is actually called either “Lazy Eye” or “Sleepy Eye”, and has more to do with the camera than the person you’re photographing. The term “Lazy Eye” is probably the most incorrectly-named syndrome ever. It usually occurs with people who have extraordinarily fast reactions – just the opposite of being lazy! And the problem has actually gotten worse (that is, it has affected a greater number of people) since the advent of flash designed for use with digital cameras (Figure 8). In the old days things were easy. Electronic flashes would flash only once and be finished. Very, very few people had fast enough reaction times to actually blink during the exposure – the blinking would usually occur afterwards. But when digital cameras came onto the scene, there was a problem: the digital sensor would not reflect the light from the flash in the same way as film did. Although nobody has ever provided me with a technical explanation that stands up to reasonable scrutiny, the widely-repeated standard explanation is it is “impossible” to measure the light bouncing off the digital sensor in real time to control flash duration (as had been done with film
Figure 8: The dreaded and poorlynamed “Lazy Eye” effect occurs when the time between the preflash and the main flash is the same as the subject’s natural blinking reflex timing.
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for 20 years). What to do? Well, all of the major DSLR manufacturers have decided to address the problem by employing a pre-flash before the picture is taken. With pre-flash, the following sequence of events occurs each time a picture is taken: 1. Once the camera has focused on the subject and the shutter release button has been pressed, the camera’s flash first outputs a very low-level “pre-flash” and then measures how much light bounces off the subject and back to the camera. (This takes place before the mirror flips up, and so the pre-flash sensors are actually sitting behind the focusing screen; the same ones responsible for the 40-segment metering.) 2. The camera uses this measurement to calculate the proper amount of light to output. 3. The mirror flips up, the shutter opens, and then the flash is told to dispense just the right amount of light, based on the measurements of the pre-flash. 4. The shutter closes. Notice a significant departure from previous flash-controlling schemes: There are now TWO flashes!! One before the picture is taken (the pre-flash), and the other during the exposure. This is both good news and bad news in terms of lazy eye: The good news is, those who had very fast reflexes and always blinked with a film camera will now have their eyes open (because the pre-flash made them blink early). The bad news is, those people who used to blink after the picture was taken now find that their blinking coincides with the 2nd flash (when the picture is being taken).
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Everybody blinks, but the new digital flash measurement system happens to catch more people blinking than the old system. What to do? Well, since everybody blinks at one time or another, it’s impossible to suggest a cure that will work 100% of the time for everyone. Having said that, here are some suggestions which may (or may not!) work, depending on your subject: 1. Switch to wireless flash. With wireless, the delay between the pre-flash and the actual flash changes, and therefore might not coincide with your subjects’ blinking. 2. Switch to wireless flash and change the f/stop. From what I’ve been able to uncover from the wireless protocol, the delay between the pre-flash and the final flash changes according to the power required of the off-camera flash. The slight change in delay may be enough to not coincide with your subjects’ blinking. (This is in theory only. When I tried it on my blinkable subject, it resulted in no improvement. See Figure 9.)
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Figure 9: Sometimes changing the f/stop when in wireless mode can alter the timing of the main flash, resulting in less of a blink. As you can see, this technique did not work in this instance.
3. Try using red-eye reduction mode. The same theory applies here: Change the timing between the initial flash and the actual exposure, and hopefully you’ll miss the instinctive blinking. 4. Try shooting several frames in a row using continuous drive mode. On the third image the blinking will be much less pronounced. (Figure 10.)
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Figure 10: Shooting three in rapid sequence can throw off they brain’s natural reflex rhythm. (Some red-eye reduction features can have this effect as well.)
5. Put the flash into Manual output mode, which uses NO preflash whatsoever. (Easier said than done, since not all accessory flashes allow you to control the output manually, nor do all camera bodies allow you to set the pop-up flash’s output intensity manually.) In manual flash mode, you’re responsible for ensuring that the amount of flash being output is right for the distance and f/stop being used – this is easily ascertained by shooting some test exposures and either changing the f/stop or the flash’s output. NOTE: If you try to put an accessory flash into manual output mode AND trigger it wirelessly, be aware that although the accessory flash will only output one Contents of this book Copyright © 2007 Gary L. Friedman. All rights reserved.
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flash pulse, the camera’s pop-up flash will still fire two pulses (since it has no idea that your off-camera flash has been set to manual output), which might render this solution ineffective. For best results, keep the accessory flash on-camera when trying this technique, or use an Infrared Filter (like a piece of exposed and developed color negative film) in front of the pop-up flash. 6. (This is an expensive measure, but it will probably address the problem!) Purchase the Metz 54 MZ-4 flash (and the dedicated Minolta adapter) as mentioned in the previous section. Not only will you get all the benefits of TTL flash metering, but you’ll also get the option of switching to AutoThrysistor mode (where the unit determines the proper flash exposure using its own built-in sensor) should your subjects display the Lazy Eye effect. So, there you have it! The long and short (long, mostly) of the annoying “Lazy Eye” effect. If none of these techniques work on your subject, you can always try shooting outdoors on an overcast day so you don’t need a flash to begin with. ☺
Figure 11: Adjusting the flash’s output manually, or using an AutoThrysistor flash (such as the Metz 54 MZ-4 accessory flash) can also solve the problem nicely!
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The Basics of Proper Exposure It’s hard to imagine what life was like before they put exposure meters inside our cameras. Before we had such convenient light meters at our disposal, there were two basic methods of determining correct exposure: Use a rule-of-thumb chart (“Sunny day: 1/250th of a second at f/16” – such charts used to be included in every roll of Kodak 35mm film back in the old days), or a handheld exposure meter, as shown in Figure 12. It is interesting to note that handheld exposure meters are STILL being used today by Hollywood filmmakers and anyone serious about photography. Why? Because they tend to give consistently accurate exposure readings in the widest set of circumstances. And it is important to understand the differences and how the exposure is actually determined if you’re going to rely on your camera’s built-in meter to make the right choice. So, read on… this is very important!! Handheld exposure meters work on a completely different principle than the ones built into your camera: Handheld exposure meters measure the light which is falling onto your subject. Built-in exposure meters, on the other hand, measure the light that is reflected off of your subject and back into the camera.
Figure 12: This is an old-fashioned (yet modern) exposure meter. They’re still being made because they still serve a useful purpose: When used correctly they will always give you the right exposure recommendations, no matter how dark or light your subject is.
Why two different methods, and which one is better? Perhaps this fictitious dialog taking place between two engineers back in Contents of this book Copyright © 2007 Gary L. Friedman. All rights reserved.
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the 1950’s might shed some light on the subject (no pun intended): Engineer #1: Well, here we are, in the late 1950’s, sitting here at this table! And we’re trying to come up with the next major improvement in photography! Engineer #2: Who the heck are you talking to? Engineer #1 (Ignoring his colleague) What would you say is the biggest problem with using today’s modern cameras? Engineer #2: Well, focusing manually is a pain, but it’ll be at least another 35 years before that problem is solved. So, I’d have to say the biggest problem is “trying to figure out what exposure settings to use”. Engineer #1: You said it, brother! Taking the picture might only occupy a fraction of a second, but determining the proper exposure is a genuine pain! Consider this list of steps needed just to take one picture using today’s technology: 1) Carry the exposure meter and place it directly in front of the subject. 2) Take an “incident light” reading, measuring the amount of light falling onto the subject. 3) Decide which combination of f/stop and shutter speed to use (many different combinations will work) 4) Go back to your camera and manually set the f/stop and shutter speed according to what the handheld light meter recommends. 5) Shoot away! Engineer #2: That does sound like a royal pain! Especially the part about having to walk all the way to your subject in order to measure the incident light falling upon it. Of course, you only have to go
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through this process once, right? Unless the light on your subject changes, the initial settings should be good for the whole shooting session! Engineer #1: That’s not necessarily true – for example, when you’re shooting sports, animals, documentaries, or any other setting where the light changes quickly. Plus, there are many times when you just can’t walk up to your subject and measure the light hitting it. Because of these drawbacks, we need to come up with a much faster method that can actually measure the light hitting the subject by remote control. Engineer #2: But… how? Engineer #1: (After careful consideration) Well, I have an idea. But I know you won’t like it. Engineer #2: Just because all of your past ideas have been stupid doesn’t mean I won’t like this one! What is it? Engineer #1: Promise you won’t yell at me? Engineer #2: (Crossing his fingers) I promise! Engineer #1: Okay, here it is… Instead of measuring the incident light that’s falling upon the subject, why not measure the light that’s reflected off of the subject and back into the camera? Engineer #2 (after pondering this carefully): That’s the stupidest idea I’ve ever heard! For starters, the amount of light reflected back will be all over the map! What if the subject is wearing a white shirt – that will reflect back MUCH MORE light than if he were wearing a black outfit! It’s a completely unreliable way to measure the light falling onto the subject! Engineer #1: Not so fast, quantum lips! While I agree that it won’t be nearly as accurate as measuring the incident light by hand, I’m willing to bet a month’s salary that the average subject (with its wide Contents of this book Copyright © 2007 Gary L. Friedman. All rights reserved.
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range of colors and brightnesses) will, on average, reflect pretty much the same amount of light, which we can then use to infer the amount light falling onto the subject, which we can then use to calculate proper exposure. So if your subject isn’t mostly black or mostly white, the camera will indeed be able to make the right exposure recommendation under the vast majority of snapshot conditions! Engineer #2: You’re insane! You’re talking about replacing a highly accurate method of determining exposure with a wildly inaccurate one, all in the name of convenience! Gary will have to write another book just to explain to people how the system works and when it will fail (and hence when to overexpose and underexpose)! Engineer #1: Hey, bro – it won’t be the first time in history that the inferior solution became the popular option of choice! Engineer #2: I still say you’re nuts! Engineer #1: Okay, let’s find out… Let’s go examine thousands of common snapshots and see if, on average, the subjects do indeed possess a common reflectivity! And so our protagonists did just that… and returned a week later with their results. Engineer #1: Well, here we are, one week later, to compare our results! Engineer #2: Why do you always have to set the scene verbally? Engineer #1: So what did you find?
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Engineer #2: Well, I went through thousands of standard “snapshot”-like images, and measured the reflectivity of the subjects. And I did, indeed, discover that, when you average everything together, the average subject reflects about 18% of the light back to the camera. Engineer #1: Ah HA! And I came to the exact same conclusion! So, when we’re designing the incamera light meter, if we take the average of all the light that is reflected back to the camera, and set the f/stop and shutter speed to make that average reflection look like 18% grey, then there’s a high probability that the image will be exposed correctly! Engineer #2: Well, you’re correct, although I still think you’re an idiot! Now if you’ll excuse me, I’m late for a meeting to discuss whether the film industry should move away from the 3-stripe Technicolor process toward something inferior like Ektachrome.. (
Note: The above made-up conversation probably occurred in Japanese. The reference to 3-stripe Technicolor was another historical example of a superior technology (one of the best color film technologies ever – the Wizard of Oz and every Danny Kaye film ever made was shot in 3-stripe Technicolor) being replaced by a poorer one (Ektachrome, whose color deteriorated quickly but was considerably cheaper.))
And so this basic principle of assuming that the average of all scenes should be rendered as 18% grey perpetuates to this day. And although it’s far from perfect (i.e., a bride with a white dress will tend to look 18% grayish instead of white, and a groom’s black tux will often look 18% grey instead of darker), on average most point-and-shooters have been very happy with its decisions. People in-the-know (and readers of this e-booklet) tend to be happy making the occasional override using their Exposure Compensation function when necessary, in exchange for the convenience of NOT having to use the handheld exposure meters. Contents of this book Copyright © 2007 Gary L. Friedman. All rights reserved.
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CenterCenter-weighted and MultiMulti-segment (or “Matrix”) Metering Metering Since the advent of the “18% grey” principle, there have been many attempts to improve upon the accuracy of the built-in exposure meter for scenes that are not “average”, such as subjects that are backlit. Usually these entail dividing the picture into smaller areas (Nikon uses 5; Minolta used 14; Sony uses 40) and analyzing each of these areas in terms of absolute light measurement (with an emphasis on what’s behind the focus point) and comparing the values against each other and against a tiny in-camera database of “standard composition” with rules like “When the metering pattern looks like this pattern, overexpose by ½ a stop; and when the pattern looks like this other pattern, then underexpose by 0.75 stops.” This technique of dividing the frame and evaluating the exposure is commonly known as “matrix metering” (Nikon terminology) or “multi-segment metering” (Minolta and Sony terminology). It tends to succeed in getting the right exposure under a wider set of circumstances than the standard 18% grey method. Old professionals disliked multi-segment metering at first, because they had invested a lot of time understanding their 18% exposure meters and knowing intuitively when they will make bad recommendations and when (and how much) to override them. In their mind, the problem with multisegment metering (and this was quite relevant in the days of shooting slides) is that you can’t possibly know how much to set your exposure compensation to since you don’t know how the camera’s meter is choosing to handle a difficult, non-average composition. (Should I overexpose this picture of a bride in her white dress, or did the multi-segment metering take that into account already?) And so, for these folks, camera manufacturers left the old metering system in the camera as a selectable option. It is called “Center-weighted” metering because the camera tended to emphasize reflected light readings from the center of the viewfinder more than the light at the corners. And aside from that slight emphasis, it made its exposure calculations based on the 18% rule, just like the cameras of the 1960’s.
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With the advent of digital, you’re not working blind anymore, plus the Multi-segment metering algorithms have a great track record of making the right choices in a wider set of circumstances. That’s why I keep my camera set to Multi-Segment metering all the time (and when the composition is really non-average, like a predominantly dark scene, I temporarily switch to either spot metering or manual exposure.)
Surprising Decisions Want to see an example of an unexpected yet perfectly reproducible decision made by the multisegment metering? Check out the collection of images below.
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Center-weighted
Spot Meter
Multi-segment
Black
18% grey
White
(huh?)
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According to the 18% principal of reflected light meters, the camera should try to make all subjects – even all-black and all-white ones -- look 18% grey. And as you can see by (most of) the examples above, the camera’s exposure meter pretty much does just that. Good. But wait! What have we here? In the lower-right-hand-corner! The multisegment metering has decided to make a white piece of cardboard actually look white!! This opens up a whole can of worms. How did the camera know the cardboard was white, and not a grey piece of Figure 13: When the light is very strong, Multi-segment cardboard with a lot of light hitting it? If metering will render a white piece of cardboard as white. the camera was smart enough to make (Upper left.) Turning the same piece of cardboard slightly so white come out as white, why couldn’t it the sun is not quite as strong renders the white cardboard as (upper right). The same test with black paper yields a also do the same for black? Would the grey grey rendering both times (as you’d expect; bottom row). same decision be made if the white What’s going on? cardboard were being illuminated by window light at dusk? If I’m shooting a predominantly white scene in the future, should I overexpose a bit or trust that the exposure meter will recognize this as being white and compensate accordingly? Contents of this book Copyright © 2007 Gary L. Friedman. All rights reserved.
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(You can see now why the pro’s eschewed Multi-segment metering in the early days – nobody likes surprises, especially when your next meal is dependent upon the shot coming out the way you had envisioned and intended!!) This unexpected result fascinated me to no end, and so more experimentation was necessary in order to understand how the camera makes its choice. I tested under various types of light with various intensities and color balances. I tried to fool the meter. Here’s what I think the camera is thinking as it makes its decisions: 1. If there are equal amounts of red, green, and blue in the metered area, AND
Figure 14: An example where this unexpected metering anomaly actually comes in handy. This image was taken with a Konica Minolta A2, which also seems to expose for whites intelligently.
2. The color balance is in Daylight mode, AND 3. If the overall exposure value (EV) (sometimes called “Brightness Value” in the EXIF headers) is above a certain threshold, 4. THEN overexpose about 1 stop to render the metered area as white rather than grey. Mind you, this is only a hypothesis, and even after a few days of testing I’m no more closer to predicting when the camera will or won’t exhibit this behavior. But at least I now understand that the
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camera will sometimes make correct exposure decisions when I would have expected it to underexpose dramatically (like in Figure 14)!
Combining Zone Matching and DRO And while we’re on the subject of understanding how the meter behaves under non-average lighting, let’s examine in closer detail two options which your camera might offer you for handling compositions with a wide range of brightness values: Dynamic Range Optimization (often referred to as “DRO” or “DR+”; Sony Alpha only) and Zone Matching (“Hi, and Lo”, appearing on the Konica Minolta 5D, 7D, and Sony Alpha cameras). Recall that, while neither of these features actually expand the dynamic range that the sensor can capture, both of them can increase the apparent dynamic range of the final image. Essentially, they do what you would do if you shot in RAW and post-processed the highlights or shadows to “bring them out” from the left or right edges of the histogram. My main curiosity was how these two dynamic-range-affecting functions would behave when asked to work together – for example, what would happen when you turned Zone-Matching-Low ON, and also had DR+ on (which lightens the shadows in certain situations) as well? Also, how useful is Zone Matching – High in a studio situation with lots of whites? To find out I set up a “high key” (mostly white) and a “low-key” (mostly dark) scene and shot 9 images varying the Zone Matching and the DRO settings. The results appear in the two tables that follow.
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Hi-key scene
Normal 200)
(ISO
Zone Matching Low-80
Zone Matching High-200
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DRO Off
DRO
DR+
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Note that all of these the images are straight from the camera; in the real world they would probably receive post-processing before being handed over to a customer. They remain in this unfinished state simply so you can see the effect of the various settings. Also note that, as expected, the DRO had no effect on the high-key scenes (it was only designed to handle shadows, and even then it does so at its own discretion). Also as expected, the Zone matching Low-80 (designed for dark scenes) wasn’t a good match for a high-key scene – the blacks were washed out so much that the image looks of low-contrast. Zone Matching with Hi-200 did a pretty decent job keeping the detail in the white, but I don’t feel it results in a more-useable image than the one without Zone Matching. The Low-key scenes are next…
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Lo-Key Scene
Normal 200)
(ISO
Zone Matching Low-80
Zone Matching High-200
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DRO Off
DRO
DR+
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Surprise #1: DRO had absolutely no effect in any of these shots. (I had expected it to lighten the shadows in columns 2 and 3…) Surprise #2: Well, it’s not really a surprise… Zone Matching Lo-80 did a terrific job bringing out the shadows in this series (as it was designed to do). I will definitely use this in all of my low-key portrait sessions in the future. Why didn’t we see a difference in DRO usage for the low-key shots? A quick consultation with David Kilpatrick, editor of Photoworld magazine and who personally interviewed the CEO of the company which makes the DRO+ algorithms, yielded the answer: “The dark suit doesn't have enough dynamic range - DRO+ will identify it as a dark area, and leave it alone. What DRO+ looks for is a low mountain range sitting in an area of high mountain ranges, but with a similar depth of valleys and peaks. It then raises the level of the low range and exaggerates its valleys and peaks a bit. What you have given it is a desert and mesa, and it doesn't decide to raise the level of the desert - that would just flatten the landscape. DRO+ would work well with a white background with some detail, and someone badly lit wearing clothes with some variation in tone, not just black or white. A tartan jacket would be ideal! It has to analyse the image and find significant detail (composed of tonal variation) present at a relatively low brightness compared to other significant detail. It will then selectively enhance that detail, but leave plain zones of black or white alone. You gave it the bits it mainly ignores - the highlights and the shadows. It works on over-dark midtones when highlights and shadows are present. –David” In other words, I had created a poor test! But in the process I realized that it doesn’t make any sense to combine DRO and Zone Matching Lo-80 – they both are useful in different circumstances, and none of those circumstances overlap. Contents of this book Copyright © 2007 Gary L. Friedman. All rights reserved.
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An Incident Light Meter That’s Always With You Okay, let’s go back a few sections, when we talked about incident light metering (using a handheld meter to measure the light falling onto the subject). There’s an old trick that the pros used during the ‘50’s and ‘60’s to duplicate the accuracy of incident exposure readings without the hassle of having to carry the light meter with you everywhere you go. It is outlined below: 1. Put the camera into spot meter mode 2. Hold up your palm so that it is being illuminated by the same light as that hitting your subject. 3. Meter off the palm of your hand, and invoke AEL (Exposure Lock) 4. Set exposure compensation to +1 5. Shoot away! As long as the light hitting your palm is the same light that’s hitting your subject, your exposures will be dead-on. Counterintuitive as it may seem, I have found that this technique works on all palms, regardless of race. It can be especially handy when shooting sporting events (like football games) at night, or for the difficult lighting situation
Figure 15: Spot-metering off of my palm (left) and then overexposing +1 stop (right) is a very quick way to accurately meter the incident light – the reading will always be accurate, and you never need to carry a handheld light meter with you!
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in Figure 16. Why does it work? The palm tends to reflect about 35% of the light (about twice as much as the 18% of an “average” scene), and so when the spot meter sees your palm it will recommend half as much light (1 stop less) in order to expose for it “correctly”. That’s why step 4 is necessary – doubling the amount of light will get the exposure back to where it should be for the light being measured. Since I have my AEL button set to “Spot AE Toggle” (via the Menus – check your camera’s instruction manual or one of my books), and since I have the front control wheel on my 7D set to exposure
Figure 16: Here’s another difficult exposure – a Caucasian foot on a black sand beach. Whereas Automatic Exposure will try to make everything come out grey, we all know that won’t be acceptable for sand that is so spectacularly black. The fastest answer was to meter off the palm of my hand and then use the Exposure Compensation function to increase the exposure by +1 stop. It took less than a second to take the 2nd shot, and I knew this difficult exposure would be rendered correctly without even looking at the captured image afterward. Contents of this book Copyright © 2007 Gary L. Friedman. All rights reserved.
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compensation, it takes no longer than one second to aim the viewfinder’s center circle on my palm, hit the AEL button, and then dial in +1 exposure and start shooting, confident that the exposure will be dead on. A VERY useful technique!
Figure 17: A day with poor light and a bright subject can really throw off an automatic exposure meter (left). Using flash outdoors in these situations can make a huge difference. Turning ADI to “On” (default) helps to ensure that the bride’s dress turns out white rather than grayish.
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To Raw or Not too Raw? A lot of strong opinions can be found on the Internet regarding RAW mode and its benefits. But there are some drawbacks to using it as well, most of which fall into the category of “It’s more work.” Is it right for you? Here are some tradeoffs: “Pros” for using RAW: 1. You will attain the very best quality that your camera has to offer 2. There are no .jpg compression artifacts. 3. It is possible to extract slightly more dynamic range from your image – you can rescue an image that otherwise would have been “blown out” had you exposed for it incorrectly in .jpg 4. There are 16-bits per color, vs. 8-bits per color with .jpg. This, again, will come in very handy should you need to compensate for gross exposure errors or make other large tweaks in Photoshop. 5. You don’t have to worry about the camera making poor white balance settings – white balance is done by the photographer, after the fact, at the computer (as are other settings such as contrast and sharpness). 6. You can easily make museum-quality, wall-sized enlargements that will look better than if you had shot with .JPG. 7. Hey, shoot RAW+JPG to be safe, and if it turns out later that you don’t need the RAW files, just delete them! IT COSTS NOTHING to have this extra level of image quality insurance!
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8. There is a very useful trick to reduce noise by overexposing in RAW and then compensating for it later in Photoshop. (You can read more about that later on in this e-booklet). “Cons” against using RAW: 1. When you’re on vacation, your memory cards fill up quickly and your hard disk storage device will have to store considerably more data. 2. Shot-to-shot times can be significantly reduced (depending on the camera). 3. You have to spend even more time in front of your computer than you do now. (I don’t know about you, but I already spend way too much time at my computer! I’d rather be out shooting than tweaking.) 4. Unless you’re showing your images to another photographer or someone in the art or publishing worlds, nobody (and I mean nobody!) will be able to see the difference. (And this is doubly true if you’re only printing small sizes, like 8.5x11” or less.) 5. It’s better to take the time to set your exposure accurately to begin with, rather than to have to “rescue” your bad exposures from RAW later on. 6. You can correct color balance issues in Photoshop (or the software of your choice) – and will look pretty much the same as if you had shot in RAW and set the color balance later. (Again, this doesn’t apply to gross exposure errors, which you shouldn’t be making in the first place.) 7. Most of the extra dynamic range captured in RAW will not be visible in the output (whether it’s inkjet or photographic prints or CRT or projection systems) – in fact, most commercial printing
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systems insist on accepting TIFF or JPG files for printing (which only have 8 bits per channel instead of RAW’s 16). 8. If I had the luxury of overexposing (for the purpose of correcting for it later to lower the overall noise), I would shoot at a lower ISO in the first place, thereby achieving lower noise! (It turns out that this line of reasoning isn’t true – see the section on Noise later on in this e-booklet for some interesting experiments!) Now that I’ve laid out both sides of the issue, I’m sure I’ll get lots of hate mail from both camps filled with religious fervor. The fact is, as with a lot of things, all arguments are correct, and there’s no “right” or “wrong” path to follow. There is only what is right for you, your sensibilities, and your tolerances. That’s why the camera offers so many different options – so you can choose the one that’s right for you. What do I do? Unless I know this will be an image for sale or an image that I will enlarge to extreme proportions, I tend to shoot in the highest quality .jpg that my camera has to offer. I switch to RAW+JPG only for the shots when I know that post-processing will be difficult (like when there’s a large tonal range), in which case I will also shoot with a tripod and bracket like crazy. Working in this way saves me great amounts of time and memory storage space. One of my heroes, Dan Heller (www.DanHeller.com), has written an eloquent piece about this subject. You can read it here: http://danheller.blogspot.com/2006/07/business-aspects-of-raw-vs-jpg-mode.html. And, to balance out this view somewhat, here is a very well-written piece about the pro’s of shooting RAW from Luminous Landscape: http://www.luminous-landscape.com/tutorials/understandingseries/u-raw-files.shtml. Remember, there is no wrong way or right way to do anything. So, please – no hate mail!
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Two Examples of Image Recovery Using RAW Here is an extreme example of recovering an image from a RAW file and a .jpg file. The images below were severely underexposed because I shot before my flash had enough time to recycle. (It was a bad picture anyway… she had her eyes closed. And the background was uninteresting. But that’s not important now…) I was shooting RAW + JPG mode, and by best estimates these images were underexposed by about 4 stops.
Original .JPG – Underexposed about 4 stops
Original RAW – underexposed about 4 stops
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JPG adjusted using Photoshop Curves
RAW adjusted via Adobe Camera RAW
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A correctly-exposed image (for reference)
To tweak these images, I opened them up in Photoshop and used the Curves tool to increase the midtones excessively. As you can see, there is a huge difference between the quality of the final images. What you see here is widely referred to as “Being able to bring out the shadows” of a RAW file – the detail is there! To some people this alone represents a compelling reason to shoot RAW – it is insurance against exposure catastrophe. But in my mind, although the recovered image quality from the RAW file is significantly better than that of the recovered .jpg, it’s still nowhere close to being a shot I can sell (or use on somebody else’s Christmas card). So just like there is no substitute for proper focus, there is also no substitute for proper exposure regardless of whether you shoot RAW or not.
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Another Example Here’s another example showing how you can actually expand the tonal range of an image using RAW files. And this time, I’ll use Photoshop CS2 to demonstrate a multi-step method of fixing local exposure errors. I use Photoshop rather than the software which came with your camera because, well, Photoshop can do this and the original manufacturer’s software can’t. The image we’re going to use is an image I shot while in New York City. This is Yet Another Example of an image that looks great when you’re standing there but comes out quite different when you take a picture of it. The building looks great, but the figurine to the left is so dark that it may as well be silhouetted. (This is, once again, due to the narrow dynamic range that a digital sensor can capture compared to the human eye.)
Figure 18: It looked great to the naked eye, but the digital sensor could not capture both the highlight (Chrysler building) and the shadow (figurine atop New York’s Grand Central Terminal).
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Fortunately, I knew this would happen, and I knew a good trick to make the picture look more like how I saw it. To start with, I set my camera to shoot this image as a RAW file. Then I went home so I could tweak the image on my computer. First, I opened up the RAW version of this image, which can often look much “flatter” than the cameraprocessed .jpg. (This is normal for RAW files – it actually means there’s more dynamic range there to work with. Counterintuitive? You bet!)
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Figure 19: Opening up the RAW file produces this intermediate screen which allows you to tweak the basic exposure and color balance settings. Once you adjust the settings you want on the right, clickContents “Open”. of this book Copyright © 2007 Gary L. Friedman. All rights reserved.
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While in the intermediate screen I made the whole picture darker so that the building came out the way I wanted it. Then I hit “OPEN”, bringing it into Photoshop.
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Then I opened the RAW file again, and this time while in the intermediate screen I tweaked the exposure so the figurines looked good. Then I hit “OPEN”.
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This leaves me now with TWO versions of the same image — one where the building is exposed well, and one where the figurine is not too dark. Next, I take one image, perform a SELECT ALL, COPY, and then I switch to the 2nd image and hit PASTE. Magically, a new layer is added to the second picture, perfectly aligned on top of the first. You can click on one layer or the other (red circle) to work on it. In this case, I’ll highlight the lighter layer with the properly-exposed figurine.
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Using Photoshop’s toolbar, I select the Eraser tool (red circle) and set it to about 81 pixels wide and fuzzy (yellow circle). (Watch what happens next…)
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Using the ERASER function, I removed the parts of the image that were blown out. In this illustration I’m showing you what information I removed…
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…but if you did this yourself you’d see the information from the layer below showing through where the pixels were removed. Voila! The image is now closer to the way I saw it, with none of the badlooking artifacts that can occur when you try to lighten the shadows from a .jpg!
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(Note: Photoshop CS2 has a function called FILE AUTOMATE MERGE TO HDR… which is supposed to combine multiple images from bracketed exposures automatically. I never really liked the decision this function made… and so I use the method described above instead.) For situations where the dynamic range is far wider than in this example (10 stops or more), put your camera on a tripod and take several identical images, each one stop apart, and then merge them in photoshop using the method above. Because you used a tripod all the images should align exactly when they are merged.
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High-Speed Sync (HSS) at High Speeds Have a look at the table below:
1/60th f/8
1/125th f/8
1/250th f/8 (HSS)
1/500th f/8 (HSS)
1/1000th f/8 (HSS)
High-speed Sync (HSS) allows you to shoot flash at any shutter speed without the “half frame” syndrome (as shown in the last image). As your shutter speed increases, though, the “reach” of the flash will be severely curtailed. (See text for nuances.) 1/2000th f/8 (HSS)
1/4000th f/8 (HSS)
th
1/250 w/o HSS
(What better test subject than a decapitated Raggedy Ann doll?)
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The reason High Speed Sync is so important is because, before it was invented, when you were shooting with flash you could only shoot up to a certain shutter speed (up to 1/125th or 1/250th of a second for film cameras, but 1/125th of a second or so for digital cameras so as not to induce too much vibration which the anti-shake mechanism must counteract). Why couldn’t you shoot faster than that?? Well, because in order for a flash picture to come out properly, the following would have to happen: 1. The first shutter curtain opens ALL THE WAY. 2. The flash fires. 3. The second shutter curtain closes. In order to obtain fast shutter speeds like 1/1,000th of a second or 1/4,000th of a second, camera companies had to employ clever techniques such as “release the 2nd shutter curtain before the first one opens all the way”, resulting in what is essentially a “Traveling Slit” across the sensor. If the shutter never opens completely, a flash burst that lasts only 1/10,000th of a second (!) will only expose part of the frame – the part where the slit happens to be. As an example of this, consider the very last photo in the table above labeled “1/250th w/o HSS” (translation: a shutter speed of 1/250th of a second without using High Speed Sync). Here, the 1st shutter curtain only opened halfway when the flash fired, exposing only half the sensor. HSS is a very clever invention that eliminates this problem. As described in the book, the flash is capable of outputting (yes, that’s a word) a series of low-intensity pulses over a slightly longer period of time rather than one large one. In this way the flash acts more like an ambient light rather than a flash – a light that’s always there for the duration of the exposure, and hence always there to expose each part of the sensor as the traveling slit goes across it. That’s all fine and good, BUT you should know that when you shoot at increasingly faster shutter speeds, it’s possible that your subject will slowly start to get darker (as in the example above). Why is
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this? Well, it turns out that like most things in life, there is a tradeoff. In this case, with HSS the faster your shutter speed, the less reach your flash will have. At speeds of 1/4000th of a second at f/8 and ISO 100, your subject must be 5 feet or closer to the flash in order to be properly illuminated. (Not ideal for sports photography!) HSS was really designed for one thing: allowing you to take pictures like that shown in Figure 20. Normally, if you’re taking a picture like this on a bright, sunny day, and you want out-of-focus backgrounds, you’d want to use a lens such as the 70-200 f/2.8 SSM (or its earlier version, the 80-200 f/2.8 which is just as sharp). At such large f/stops, the ambient light dictates that a fast shutter speed be used – usually much faster than the 1/125th of a second flash sync speed of the shutter. Under these circumstances it would ordinarily be impossible to use flash, but with HSS (as long as the subject is reasonably close to the flash), it can work and provide the kind of good light that makes an image stand out.
Figure 20: A good example of where HSS is quite useful - allowing you to shoot on a sunny day, using large f/stops (yielding shallow depth-of-field) and fast shutter speeds, and still use flash for illuminating your subject.
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The Noise about Noise I haven’t discussed this subject much in my books, but if you spend any amount of time online in an internet discussion forum (especially those discussing the Sony Alpha 100 or the Minolta Dimage A1 or A2 digital cameras) you will hear no end of cacophony lamenting the amount of noise at high ISO settings. The reason I haven’t talked about it much is because I feel this issue is so blown out of proportion that trying to add a semblance of level-headed perspective (as many others have attempted to do) to the subject ultimately results in your voice being drowned out. This e-booklet is a different arena, however, since in my prior life as a consultant I’ve learned that people tend to believe advice that they pay for over identical advice that they receive for free elsewhere. ☺ And so, here is my perspective on the issue of noise:
Figure 21: A handheld shot taken by campfire at ISO 1600 by a KM 7D. If low noise is what you seek, then nothing beats the 7D or the 5D (which use the same 6 Megapixel sensor).
• All digital sensors have noise at high ISO. The physics of sensor design dictate that the noise will increase as the pixel size shrinks (as in the Dimage A1 and A2), or as the pixel density increases (as in Sony’s 10 MP sensor, versions of which are used in the Pentax 10D and most of the Nikon lineup (except the D2X) as well as the Sony Alpha 100).
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• The amount of light on the subject influences the amount of noise you can see. If you’re shooting in a dark room with poor light and your histogram looks heavy on the left side (lots of darkness and shadows), that’s where noise will be most prominent. If on the other hand your subject is well-illuminated (and its associated brightness shows up in the right-hand half of the histogram), the amount of visible noise will be markedly decreased. (See below for more detail on this characteristic). • High ISO 35mm film showed much higher levels of noise (affectionately referred to as “grain” by film lovers and for some reason never complained about in online forums). If I didn’t want grain back in the film days, I’d simply shoot with a lower ISO film. The same rule applies to digital. If I have to shoot at high ISO, I would vastly prefer the digital noise at ISO 1600 over the film equivalent. • When designing in-camera image tweaking algorithms (i.e., the software used by the camera to create .jpg’s), there is a continuous tradeoff between sharpness and noise. Cameras which use the Sony sensor that display less noise in their .jpg’s also display less detail. You can always reduce noise after the fact (via post-processing software tools such as Noise Ninja (http://www.picturecode.com), NeatImage (http://www.neatimage.com) or Noiseware (http://www.imagenomic.com/, who ironically also make software to add film graininess to your image)), but you can never restore detail once it’s been taken away by in-camera .jpg noise removal. I’ll take the sharper image any day! Okay, enough talk. How bad is this “noise problem” anyway? Figure 23 shows some comparisons taken with the Konica Minolta 7D (6 MP), Minolta A2 (8 MP), and the Sony Alpha 100 (10 MP). And, just as a reference point, compare these noise levels with an ISO 1000 image taken with conventional B&W film from the 1970’s (Figure 24).
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Figure 22: Back in the days of film, I invented an automatic exposure bracketing device for making time exposures incredibly easy. Once the camera was set up on a tripod and set to “B” (long exposure) mode, I would hook up my Hewlett Packard 41C programmable calculator with the special interface circuitry to my camera, and tell the camera “Take six pictures in ½ stop increments, starting with a 2-minute exposure”. And the calculator would dutifully take six pictures of 2, 3, 4, 6, 8, and 12 minute duration – all while I stayed inside where it was warm. I’m using this image for demonstration purposes because, well, I’m tired of using stuffed animals for test subjects. ☺ See Figure 23 for enlargements of the yellow box.
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Figure 23: Enlargements of the yellow square from Figure 22 taken with three different cameras. From left to right: 1) The KM 7D (6MP at ISO 1600), 2) the KM A2 (8 MP at ISO 800 (as high as it could go)), and 3) The Sony A100 (10 MP at ISO 1600). As one would expect, when compared to the A2 the Sony isn’t so bad. The noise is tolerable when making 4x6 prints, but can be quite noticeable when printing to 8.5 x 11” or larger.
Some people have no problem with noise; they are usually happy just to have a shot which was taken under difficult circumstances. Others are not so easily pleased; and will often stress out as if noise were somehow more important than an interesting image. (Both points of view are perfectly valid, by the way!) And I will say that I once was in the first camp. Then I went to China for six months in 2003, taking with me only a Minolta A1 and leaving my film cameras at home. You can see the results of that trip at http://friedmanarchives.com/China/Page1/index.htm . Have a look at some of these images; you will notice that quite a few of them were shot at high ISO (which I had to do because of poor existing Contents of this book Copyright © 2007 Gary L. Friedman. All rights reserved.
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light and I couldn’t use a tripod which would have allowed me to use a lower ISO setting) and have noticeable noise. Although I was lamenting the noisiness of the images at first, that uneasiness faded over time and now all I see is the image (composition and light). When word of the China gallery reached a discussion forum on dpreview.com (http://forums.dpreview.com/forums/readflat.asp?forum=1024&message=11955568&q=gary+friedman s+china&qf=m), the issue of noise did indeed come up only once, and here are excerpts from my
Figure 24: This existing-light shot was taken with ISO 1000 B&W film and developed normally. Although the grain gives the image a certain old-world charm, I vastly prefer the lower noise of digital for such work.
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responses: Most of the noisy images were taken in existing light using ISO 800. I believe that any digital camera available at the time would have handled the situation similarly. I don't mind; I got the shot and in situations like this where you can't control your environment or the subjects, the shot is far more important than the noise. I have always believed that the more compelling the image, the less important the technical issues. Think of the more important images of the past - Kennedy after he was shot, Elvis meeting Richard Nixon, the protester standing in front of a tank at the Tien An Men Square uprising, Rodney King beatings (although that was video tape),... All of these images were technically sub-standard, and yet nobody ever commented about them being underexposed, too grainy, or that the lens that took them had 0.2% pincushion distortion at the wide end. Powerful images do not need technical finesse!! It is important to note that high ISO doesn’t always mean lots of noticeable noise. Check out Figure 25 which provides an example. The reason for this will be described in the next section: illumination that falls to the right in the
Figure 25: A well-lit image shot at ISO 1600 can have very little visible noise.
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histogram tends to look quite good, whereas light which falls to the left (‘shadows’) will have the most visible noise.
Some things you can do As mentioned earlier, there are some software packages that allow you to reduce the amount of noise (usually at the expense of retaining detail) in your images once you get back to your computer. (See Figure 26 for an example of noise reduction using Noise Ninja.) If you’re a user of Photoshop, there’s also the old trick of using Filter Noise Reduce Noise… and then select “Advanced” and have it operate on the blue channel only, the channel which tends to contain the majority of visible noise in an image. This is an intermediate technique which can reduce visible noise without sacrificing as much detail in your image. Earlier in this e-booklet I mentioned a technique that has come to be known as “Exposing to the right”, where you overexpose an image in RAW (careful not to blow out the highlights!) and then correct for it later, with the result being a lower noise image. Figure 27 shows an example of this technique in action. The principle is the same as the one at work in Figure 25; that is, if you’re careful to place the subject’s brightness range into the right-half of the histogram (and taking care not to over-do it and blow out the highlights), you’ll significantly reduce the visible noise. To achieve this noise-reducing technique, I performed the following steps: 1. Put the camera into RAW + JPG mode 2. Overexpose by about 1 stop (your mileage may vary; the idea was to get the bright areas of the histogram shifted to the right without actually “clipping” or blowing out the highlights). 3. Open the RAW file using Sony’s Image Data Converter SR software.
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4. Use the Tone Curve to darken the image, and restore the histogram to what it was before you overexposed it in Step 2. (See Figure 28.) A more technical explanation of this technique can be found on the Luminous Landscape website: http://www.luminous-landscape.com/tutorials/expose-right.shtml .
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Figure 26: A handheld image from the inside of an aircraft carrier shot at ISO 1600. (“Male Berthing” – that’s funny! ☺) The lower-left image shows a close-up of the original image (corner); the lower right shows the same image post-processed using Noise Ninja. The downside to this technique is you can sometimes lose detail if you apply too much noise removal.
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Figure 27: Sony A100 shot at ISO 1600 (left) and the same scene at ISO 1600, overexposed using RAW and darkened in post-processing (center). Tremendous reduction in noise, but how does it compare with just shooting at a lower ISO to begin with? The answer is in the right image, which was shot at ISO 800, and has more noise than the center RAW image shot at 1600! As unintuitive as it is, it seems to be better to overexpose at a higher ISO and post-process later to reduce noise!!
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Figure 28: Post-processing the RAW image using Sony’s Image Data Converter SR software. To darken the image and shift the histogram back to the left, grab the tone curve in the center and pull it down enough to darken the image. You will see the histogram move to the left when you let go of the mouse. You can then save the image as a .tiff or a .jpg.
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Cold Weather Operation I grew up in California (where I still live), so you could argue that I have no idea what cold weather is. (And you’d be right!) However, I can tell you one thing about today’s digital cameras that make them significantly different from the old film cameras of the 1950’s and 1960’s: Because of their electronics, they can’t perform nearly as well in extremely cold weather. The Sony Figure 29: How to connect wires to your camera’s battery. The Minolta battery on the left can be connected to using alligator A100 camera is rated to work between clips and rubber bands, and then sealed in a container with 32-104° F/0-40° C, but with a little strain relief, The Sony on the right can be tapped via alligator effort you can probably use the camera clips and paper clips into the rightmost and leftmost holes. in much colder conditions. There are lots of culprits of why a camera will stop working in cold wether – the one thing you’re most likely to read about elsewhere is the lithium-ion batteries, which stop working at around 0 degrees Celsius. (Interestingly, this is also what the Alpha camera is rated at – how much of that rating was due to the battery?) But there are other factors as well, and so what I’d like to do is spell out the problems you’re likely to encounter as you shoot outdoors in progressively colder weather:
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Figure 30: This picture was taken on Super Bowl Sunday in Chicago, when the Chicago Bears were playing the Indianapolis Colts, and all of the city was rooting for their home team. On this night it was about minus 17 degrees F (with wind chill); and it took me about 20 minutes to get this shot. Had the battery stayed in the camera I probably wouldn’t have been able to snap off more than 20 shots; however in this case the battery stayed warm in a pocket close to my body so I could shoot many more frames until I got one I liked. (The Bears lost, by the way.)
BATTERIES: The batteries will be the first to fail. According to one digital photographer who wrote about his experiences shooting at Alaska’s Iditarod race, during the cold temperatures he was only able
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to squeeze 5 shots out of his camera before the battery died. This is because as the temperature gets colder, the ability for the Lithium-ion batteries to deliver energy is greatly diminished (it’s not fatal though – they will start working normally again once they warm up). This is the rationale behind the oft-heard recommendation “Always keep spare batteries under your coat, next to your body to keep them warm until you need them”. This isn’t bad advice, however it means you will be swapping batteries a lot. A better solution (if you don’t mind a little extra effort) is to keep the battery next to your body and tether the battery to your camera. There are two ways to do this that I know of, and they are illustrated in Figure 29 and Figure 31. And while I realize that most people do not feel electronically inclined, there is nothing here that is horribly difficult. “Alligator Clips” (sometimes called “Croc Clips” in the UK) are easily obtained at any electronics hobbyist store, and, like duct tape, have been known to hold the world together. They can instantly create a connection from one metallic surface to another. In this case they will bridge the space between the metal on the battery’s contacts, and their corresponding mating contacts within the battery chamber. The method pictured in Figure 29 and Figure 31 will work for any camera. Two different alligator clips are attached to the battery via either rubber bands (Minolta) or paper clips (Sony), and then these clips are clamped to the same
Figure 31: A slightly easier way to attach a tethered battery to either Minolta or Sony cameras – have the alligator clips directly clamp onto the contacts in the battery chamber. (Make sure you tape the wires to the camera body for strain relief.)
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contacts that the battery’s contacts would normally mate with had it been inserted normally. (In other words, don’t cross-wire them and hook the battery up backwards!) The battery and clips, once secured, should be mounted in a protective housing (the cardboard core of toilet paper works nicely) and the wires taped to the outside edges for strain relief. Ideally about 3-5 feet of wire between the camera and the battery will be more than enough to freely place the battery anywhere it will be warm, and allow great freedom in manipulating the camera and changing lenses out in the cold.
Figure 32: The preferred way to attach a tethered battery to a Minolta digital camera. Use a Radio Shack (“Tandy Electronics” in the UK) “Adaptaplug type B” and “Adaptaplug Socket”
If you own a Konica Minolta digital camera, there’s an easier way to attach the battery to the camera: the external “DC In” connector lets you feed the external battery’s power via a commonly available connector. (See details in Figure 32.) Such connectors are not so easily available for the Sony cameras, since they chose a non-standard connector to accommodate their external power. The only way to connect to Sony’s external power plug is to purchase one of their dedicated AC adapters (AV-VQ900AM, if you can find one), cut off the cord near the part that plugs into the wall, and then attach these leads to your battery via the clips. Once you get the external battery connected and working on your camera, you can actually replace the battery with a set of 6 “C” or “D” batteries (as pictured in Figure 33), again keeping them at working temperature by keeping them close to your body) and have the batteries last about 10 times longer out in the field. Although in theory only 4 such batteries are
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needed to generate the required 6V, in my own experiments I’ve found that 9 volts are actually required, especially if you’ve got a long wire going to the camera (which usually has a lot of resistance to overcome.) Don’t worry; the cameras have internal voltage regulators so feeding it too much voltage won’t damage it. (I also discovered that the cameras have built-in reverse-polarity protection, so if you happen to hook up the camera backwards you won’t actually damage it.) CONDENSATION: Once you get the battery issue taken care of, the next issue you’ll be fighting is moisture and condensation, both of which can cloud your optics and ruin your ability to get good shots long before your camera fails. Usually condensation will Figure 33: You can use 6 “C” or “D” occur during transitions between the warm, often moist batteries together instead of the camera indoor environments to the cold, sometimes dry outdoor batteries. As long as they are kept warm, environments. (And in the opposite direction as well!) they should last substantially longer out in In these cases just doing nothing for five minutes the field. (Here it is being shown attached to should be enough time for the condensation to go away a 7D via the “DC In” jack. See text on how to connect to the Sony Alpha.) on its own. Sometimes your own breath on the camera will cause problems too – it could easily condense on the lens, or elsewhere on the camera body, and there are plenty of places on the camera (knobs, buttons, etc.) where this moisture can creep in and condense onto the delicate electronics, causing no end of operational failures.
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The threat of moisture and condensation intensifies greatly if you change lenses out in the cold (or at times your camera is prone to condensation, such as when you bring it from a cold environment into a warm, humid one.) For taking your lens off exposes critical components to the elements; namely the shutter and the sensor (but it also exposes lots of non-sealed areas in the mirror box into which moisture can creep). Moisture can accumulate on the shutter blades, and then freeze if it gets cold enough, making the shutter inoperable. Probably the best protection against moisture is to use the infamous Ewa Marine underwater camera bags (www.ewamarine.com). If your camera is in a dry room when sealed in this bag, it will completely eliminate the threat of moisture in outdoor, cold-weather operation. If you also tether your camera to batteries worn next to your body, then you’re addressing both major impediments to shooting in cold weather. LCD DISPLAY: The LCD readout on the back of the camera will be the next to go. Your camera will still capture, process, and store the image onto your memory card; however you just won’t be able to see it on the LCD screen. Like the batteries, when the temperature warms up again, your display will revert to normalcy, having suffered no ill effects. COLDER STILL: As the temperature gets even colder, your digital camera will fail. It could be any number of things that trigger it – the anti-shake (sorry, “Super SteadyShot™”) mechanism could stop working, moisture could freeze on sensitive parts (as discussed in the previous section), or the electronics will just stop working. That’s the nature of the beast. Most photographers who just want to shoot cold weather pictures as a hobby will probably throw in the towel at this point and say “This is too cold – I’m going inside.”. Professionals, scientists, researchers, or people who are just plain determined may wish to keep going, however.
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If you STILL want to shoot at this subzero stage, then say hello to our old friend “The Mechanical film SLR” from the 1960’s. (I own two that can be used in Siberia in the wintertime! See Figure 34). The Minolta SRT-series, the Nikon F or F2, the Canon F-1, or any other allmechanical camera with a horizontallytraversing cloth shutter curtain all have shutters that can work without batteries, and have the ability to work in temperatures as low as -100 F! Figure 34: Nothing beats these all-mechanical film-based (Horizontally-traversing cloth shutters SLRs from the 1960’s (and, in the case of the Russian Zenit were preferred over the vertically- camera on the right, circa 1988) for extremely cold shooting traversing metal blade shutters because conditions. These will continue to work in the cold long after the vertical metal blades are susceptible the electronics in your digital camera have died. (Make sure to tiny droplets of water vapor which can you keep a handheld exposure thmeter close to your body, or just shoot negatives at 1/125 of a second at f/5.6 and freeze, rendering the shutter useless.) correct for exposure errors at the lab. ☺ ) Mechanical rangefinder cameras, such as most of the classic Leica M series, are ideal for this kind of work as well. Of course there are caveats to using mechanical cameras in cold weather as well. For one thing, at -100 F the film will get brittle and snap, or static electricity will build up and discharge with a spark (fogging adjacent frames) as the film is advanced. And the lubrication which protects the camera’s mechanical parts from wear can become so viscous that it can actually goo up and prevent parts from moving! (In the old days (like when people knew what a mechanical camera WAS), professional photographers Contents of this book Copyright © 2007 Gary L. Friedman. All rights reserved.
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working in extreme cold would often have their cameras “winterized”, where the factory service would remove all internal part lubricants so that the camera would still work.) I have never actually had the pleasure of shooting in conditions so cold that I needed to revert to my mechanical film cameras. But here are the writings of someone who has, and he offers even more useful tips: http://ephotozine.com/techniques/viewtechnique.cfm?recid=75 Plus, I plan to take two cold-weather trips in 2007, and if I discover any erroneous advice in this e-booklet, I’ll email a new version to you free of charge. ☺ (A footnote about the Zenit (pronounced “Zyeh-neet”) camera – this was the most interesting souvenir from my venture into the Soviet Union back in 1988. At that time I was using my best-in-the-world Maxxum 9000 autofocus camera, and this throwback to 1940’s camera technology was the pride of the Soviet manufacturing and innovation. It had a built-in meter (on the top deck, not visible in the viewfinder) and you had to stop down manually before you could shoot. I laughed at this at first until I realized that the Zenit would probably work in Siberia in the wintertime, whereas my fancy Japanese camera would not!)
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The End Thank you for your purchase of this e-booklet! I hope at least a few parts proved to be both interesting and relevant to some aspect of your photographic endeavors. If you have any ideas for future Advanced Topics e-booklets, please let me know at
[email protected].
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