Max Out Your DSLR Sensor

Make the best exposure for a scene when you know how your camera will respond to the full spectrum, from highlights to shadows
This Article Features Photo Zoom

A. Overcast days are great for shooting intimate landscapes because of the soft, uniform lighting, but present an exposure challenge when you include the sky, which is always much brighter than the land. To capture this scene of Longs Peak from Bear Lake in Rocky Mountain National Park, I spot-metered the brightest clouds and opened up three stops. That put the aspen leaves at one stop under a midtone, within range for my sensor to record adequate detail at both ends of the tonal scale.

 


B. I calculated the exposure for this view of Delicate Arch in Arches National Park by spot-metering the bright, colorful clouds and opening up two stops, which put the shadowed rock at two or three stops darker than midtone. I used Photoshop’s Shadows/Highlights to recover good color at both ends of the tonal scale.

Sometimes your first capture is your only capture. Blow the exposure, and you’ve blown a once-in-a-lifetime opportunity. You can’t bracket high-action wildlife or outdoor sports—you’re all but guaranteed to get the wrong exposure at the decisive moment. Even landscape photographers like me need the ability to nail the exposure on the first try. I made one of my top-selling wildflower photos when the wind stopped just once during the fleeting seconds of perfect sunset light. Don’t “spray and pray,” I tell my students. Don’t turn on autobracketing, blaze away and hope for the best. Instead, I urge them, “Master the craft, and the art will follow.”

To successfully photograph a high-contrast scene with a single capture, you need two key pieces of information: What’s the dynamic range of the scene? What’s the dynamic range of your sensor? Once you have that information, you can fit the range of tones in the scene into the range your sensor can capture as well as possible.

The dynamic range of the scene is just the difference, in ƒ-stops, between the darkest important shadow and brightest important highlight. Let’s say you meter the darkest shadow and get 1/60 sec. at ƒ/2.8. (In other words, you fill the frame with the darkest shadow—nothing else—and your camera recommends an exposure of 1/60 sec. at ƒ/2.8.) You meter the brightest highlight and get 1/60 sec. at ƒ/22. The dynamic range is six stops. (Count up from ƒ/2.8 in full-stop increments: ƒ/4, ƒ/5.6, ƒ/8, ƒ/11, ƒ/16, ƒ/22.) If you expose the scene at 1/60 sec. at ƒ/8 (midway between the shadow and highlight readings), then every part of the scene that meters 1⁄60 sec. at ƒ/8 will be rendered as a midtone. The darkest shadows will be three stops darker than midtone, and the brightest highlights will be three stops brighter than midtone.


C. For accuracy, don’t include the sun in the frame when metering backlit scenes such as this view of Partition Arch in Arches National Park. To get the best compromise exposure, I spot-metered the sky near the horizon in about the middle of the arch and opened up three stops. That put the sky farther from the sun (and horizon) at about two stops over midtone and the shadowed rock at two to three stops under midtone.

The best tool for measuring the dynamic range of a scene is a handheld spot meter. It allows you to mount your camera on a tripod and compose precisely, then leave your camera locked down while you meter the scene and calculate the exposure. My Sekonic L-608 spot meter also lets me memorize the exposure for any part of the scene, such as the darkest shadow. The meter then reads out the difference, in stops, between the memorized value and the value of whatever I meter next, such as the brightest highlights. That makes it effortless to measure a scene’s dynamic range.

If you don’t have a handheld meter, use your in-camera spot meter, coupled with manual exposure mode. Almost all DSLRs will display an analog exposure scale when placed in manual-exposure mode. Point the spot meter at a part of the scene you want to render as a midtone. Green grass and medium-gray rocks often are good starting points. Adjust the exposure until the pointer is in the middle of the analog scale, indicating a “correct” (meaning midtone) exposure for that part of the scene. Now point the spot meter at the darkest important shadow. Don’t adjust the shutter speed or aperture. The pointer will move down the analog scale and tell you, in stops, how much darker than midtone that part of the scene will be. Now point the spot meter at the highlights and see how much brighter than midtone they are. If need be, switch to a telephoto to get a narrower angle of view for your spot meter.


This Article Features Photo Zoom

D. To get the best exposure for this winter scene of Capitol Peak, I spot-metered the sunlit rock and opened up two stops, which put the white aspen trunks in the foreground at about one stop under midtone. To bring back the richness of the sunset light, I decreased exposure by three-quarters of a stop in Adobe Camera Raw, then used Fill Light to restore shadow detail. If the foreground subject had been darker in tone, the dynamic range of the scene would have been considerably greater.

Some analog exposure scales only extend +2 or -2 stops from midtone. If the dynamic range exceeds that, you’ll need a different approach. Start by pointing the spot meter at the shadow and setting the “correct” exposure. The pointer will be in the middle of the analog scale. (This isn’t the exposure you’ll actually use to make the picture.) Then point the meter at the highlight, reset the “correct” exposure and calculate the difference. To avoid the mental math, you can count clicks as you adjust the aperture and/or shutter speed. Each click will represent a change of a 1/3- or ½-stop, depending on the settings you’ve chosen in your camera’s menus. If it takes 18 clicks, each representing a 1/3-stop, to go from the correct exposure for the shadows to the correct exposure for the highlights, then the range is 6 stops. It’s usually easiest to adjust shutter speed alone, since its range is much wider than the aperture range.

If you have a quick-release tripod head, you can compose your shot, lock down the tripod controls, remove the camera from the tripod head, meter the scene and reattach the camera without disturbing your composition.

Knowing the dynamic range of a scene is meaningless unless you also know how wide a range your sensor can capture. Unfortunately, camera manufacturers rarely publish a number, which means most photographers don’t know the dynamic range of their sensor—but should. In the days when nearly all outdoor photographers shot transparency film, the dynamic range of the capture medium was essentially fixed. If you were shooting Velvia, for example, you knew you had a range of about 5 stops. You could place the brightest important highlights 2.3 stops brighter than a midtone and expect bright white highlights with barely printable detail. If you placed the darkest important shadows at 2.7 stops darker than midtone, you would get dark shadows just shy of pure black.


E. This 700-year-old limber pine near Lake Haiyaha in Rocky Mountain National Park doesn’t get sunrise light at anytime of year. I placed the sunlit rock on Hallett Peak at two stops over midtone, which put the foreground tree one or two stops under midtone, using Photoshop’s Shadows/Highlights to darken the highlights and brighten the shadows.

Unlike film, the dynamic range of sensors isn’t a fixed, known quantity. In fact, it varies from camera to camera. Older, less expensive DSLRs might have a range of six stops. Newer and more expensive models usually have a greater dynamic range, as do cameras with larger sensors—perhaps as much as nine stops. The only way to determine that range accurately is by performing a simple test. In brief, it involves selecting near-white and near-black subjects and making a series of bracketed exposures, then examining the images in a RAW converter to determine the sensor’s ability to hold detail in progressively lighter and darker captures. (See the sidebar for full details.) For my Canon EOS-1Ds Mark III, I measure a range from +4 stops to -5 stops at the extreme limit, from near-white to near-black. Further testing showed I could hold reasonable color and detail over a range of about four stops (+2 to -2).

Armed with this information, I can approach high-contrast scenes with confidence. Last fall, for example, I photographed Longs Peak in Colorado framed by colorful aspen. Using a split-neutral-density filter, either virtual or physical, to tame the bright sky would have rendered the tops of the trees too dark. The fluttering leaves made HDR techniques unworkable. But my testing had showed I could spot-meter the bright gray clouds and place them three stops over a midtone. In other words, I could meter the clouds at 1/30 sec. at ƒ/16, let’s say, then open up three stops to ¼ sec. at ƒ/16. I then metered the leaves at 1½ sec. at ƒ/16, or one stop darker than the exposure I actually used (¼ sec. at ƒ/16). The final exposure gave me light gray clouds in my digital file and excellent detail in the leaves. When a shaft of sunrise light found an unexpected hole in the clouds and spotlighted the leaves, I was ready.


This Article Features Photo Zoom

F. I wanted to preserve the warmth of the sunrise light on these aspen trees in front of Capitol Peak, so I walked close enough to spot-meter the sunlit side of the trunks and opened up one stop. That put the bright sky about two stops over midtone and the shadowed snow around midtone.

Don’t assume that you can just average the shadow and highlight readings and blaze away. Let’s say you meter some shadowed flowers and sunlit mountains and determine that you have a five-stop range—within the range of almost any DSLR. “Eureka!” you think. I’ll just pick an exposure in the middle of the range and it will be perfect.

Wrong! Flowers (or at least the green foliage around them) need to be exposed close to a midtone density to look right in a print. If you choose an exposure in the middle of that five-stop range, your flowers will be 2½ stops darker than midtone, and your highlights will be 2½ stops brighter, giving you very dark, muddy flowers and washed-out peaks. If you expose the flowers as a midtone, as you should, that puts the highlights 5 stops brighter than midtone—well beyond the range of even the best DSLRs. The solution in this case almost always will be a physical or virtual split-ND filter or some variation of HDR technique.

As this example shows, your exposure strategy needs to consider the proper density for the various elements in your scene, as well as the dynamic range of the scene and your sensor. But the starting point always is this: If you know both your sensor’s and your scene’s dynamic range, you can place the brightest important highlights just below your sensor’s limit. That, in turn, will give you the best shadow detail possible in a single capture that also preserves the highlights. And if the scene won’t fit gracefully inside your sensor’s dynamic range, you’ll learn that in the field when there’s still time to do something about it.

How To Measure Your Sensor’s Dynamic Range

To measure your sensor’s dynamic range, start by selecting near-white and near-black subjects that have some variation in tone. I chose a piece of dirty-white deck furniture and a dark shadow beneath that furniture. Now make a series of bracketed exposures of each subject.

For the near-white subject, start with the exposure the camera recommends when you fill the frame with the subject and open up a 1/3-stop for each successive frame by adjusting the shutter speed in manual-exposure mode. Your final frame should be 5 stops overexposed. For the near-black subject, start with the exposure the camera recommends and close down a 1/3-stop for each successive frame. Your final frame should be 5 stops underexposed.

Examine the photos in a RAW converter (I used Adobe Camera Raw). I adjusted the Exposure, Recovery and Fill Light sliders as necessary to get the best possible detail. As you examine lighter and lighter exposures, you’ll eventually find one where you can’t recover printable detail no matter what you do. This is the point where your sensor has saturated. As you examine darker and darker exposures, you’ll eventually find one where you can’t recover printable detail without generating unacceptable noise. This is the lower limit to your camera’s ability to hold shadow detail. For my Canon EOS-1Ds Mark III, I measured a range from +4 stops to -5 stops at the extreme limit, from near-white to near-black.

In addition to knowing the outer limits of your sensor, it’s also important to know the range with reasonable color and detail. To test this admittedly subjective parameter, I photographed some flowers, bracketing +3 and -3 stops in 1/3-stop increments. I used Camera Raw to adjust each exposure to match, as closely as possible, the middle exposure in the set (the one shot at the camera’s recommendation, which proved to be correct). That testing showed I could hold adequate color and detail over a range of about four stops (+2 to -2). Images overexposed more than two stops remained pale and washed out no matter what I did. Images underexposed more than two stops became muddy with excessive noise when I tried to bring them close to midtone.

While it’s always best to expose a midtoned part of a scene as a midtone in the original capture, this second test showed I could hold decent color in parts of the subject exposed within a range of +2 or -2 stops from the meter’s recommendation.

For more information and to see more of Glenn Randall’s photography, visit www.glennrandall.com.

28 Comments

    With all due respect to Mr. Randall’s obvious skill and ability; I must ask, why complicate a simple process? Without any knowledge of my sensor’s range, I can take a point and shooter or a quality DSLR and shoot -2,0,+2 and process it through any HDR software and achieve exactly what Mr. Randall is proposing. HDR is a gift from God for landscape photographers, we really should embrace it.

    I appreciate Glenn’s detailed explanation of metering and the available range of today’s digital sensor. I think he is presenting just another alternative to those who want to get an image without hit or miss, or relying on HDR software. HDR software effects brights and shadows, and the results are not always as natural as a single image captured/processed. If your artistic vision can be had with HDR, so be it. Otherwise, this is useful information in getting the most out of a single capture. Enjoyed the example images he used as well.

    All depends on whether you are one who believes Photography is the art of capturing an image within the Camera or one who believes in post manipulation as the art. I prefer the former and use a computer as little as possible.

    Think about the first time you drove a manual transmission automobile. Now think about the 1,000th time you drove that same automobile. What was quite complicated the first time is now done with 0.1% the concentration of the first time. Not only that, but it is done much more smoothly and consistently with that greatly reduced concentration. It has become what we call, natural. Practicing what Glenn is suggesting will be complicated the first time; but when practiced over time, the procedure moves from being complicated to being natural.

    It?۪s very informative to a purely amateur camera totter like me to read how people who know how to take pictures use the zone system in digital format while keeping it simple and non-technical. That?۪s a lot more fun than program mode, and the highlights don?۪t blow out as much.

    HDR can be a very useful tool but it is not the end all Holy Grail for every photography challenge. It is not going to work very well if you have subject movement in foilage, water, etc. in landscapes. It is also not an excuse for not mastering the craft of photography and that starts by getting a firm grasp on your equipment.

    Mr Randalls very first sentance was the main resone to learn appropriate mettering. He said, Sometimes your first capture is your only capture. Blow the exposure, and you?۪ve blown a once-in-a-lifetime opportunity. That is (I think) his point in this article. Learn how to meter correctly and you’ll not have to use gimicks like HDR. Keith also makes a good point with his comment, HDR will not always work well when you have moving objects. Don’t get me wrong. people seem very adept at making bad images look better in post prossing. but this was not an article on post prossing. it was about metering and how to get the best out of your camera.

    I don’t mean any disrespect but the days of having to calculate setting are gone. I came into photogrphy in 35mm too and we no longer have to over work to produce good photos like Mr Randalls is suggesting. My Sony Alpha 350 and my Canon T2i are the work horses of todays DSLRs and PS3 is my darkroom now and no-one has to over think their shots anymore. Getting a great shot is in the eyes of the photographer today and know how to compose a picture is the art of photography now. I no longer have to work for long periods of time and take a chance on missing the shot with calculations. Now I share my shots with others by letting them see what I saw.

    Camera technology is now at the point where we can make a decent looking photograph with minimal knowledge of exposure. In fact, it wouldn’t be a huge stretch to say that you can create a print that’s every bit as expressive as Ansel’s work using a capture that was slightly off (artistic vision notwithstanding). But does that make us better photographers, or simply better at pushing a button? With the dynamic range described in Glenn’s article, there’s absolutely no reason we shouldn’t be aiming to create substantially better prints than the Masters created, rather than simply settling for “every bit as good.” Given the continuing breakthroughs in digital capture, now is PRECISELY the time to be learning the Zone System; proper exposure now allows us the ability to create a more dynamic print than ever before.

    With all due respect, if I an working on my pictures and I find that I need more out of shadows and highlights, then I get more natural looks from just doing a duplicate layer, desaturating it, inverting the values, then making the layer an overlay, then tweaking the results than I would from HDR. Unless I’m illustrating a comic book…

    But I appreciate the time and effort Glenn put in to sharing this with us. Very informative and extremely useful. Thank you Glenn.

    Thank you for the article. This is just the kind of article I have been looking for. I don’t want to rely on post processing to nail (or try to) correct exposure after the face. I wan’t to learn to get it right straight out of the camera. But, it is not a simple matter. I look forward to more articles that teach us how to properly meter and expose in difficult situations coming!

    I totally agree with some of the comment’s here. Getting the image on a single capture is the art! HDR can be gorgeous and fun to play with but almost always not realistic. Our naked eyes do not make the adjustments between the lights and shadows within a scene that HDR does. In my opinion, HDR images are nothing more than a novelty effect item rather than a tool for great photography.

    Bravo,bravo. I appreciate your article on f-stops! Finally someone who is brave enough to enlighten us about a subject no one before would alow any deliberate explaination of. The one technique I have seemed to failed to grasp. I feel this will lead to the next step in my goals of becoming something other than an photography enthusiasist/ameture photographer.I wait paitiently for continuing articles about the “craft of photography”.

    Interesting article. As I read it this is not about HDR or not but about getting as much you can from a single exposure (and even HDR are composed by just that – single exposures). One thing I don??t see explained is how to define middle exposure – is that a constant or a relative thing?

    I’m a little confused. 1?_ sec. at ??/16 is not one stoP below ?_ sec. at ??/16. It’s about 2 and two thirds. It makes the article hard to undestand for a newbie like me.

    I’m a newbie. The article makes sense but how the author goes about fitting a scene’s dynamic range onto a sensor doesn’t make sens to me. For examlPle, 1?_ sec. at ??/16 is not 1 stoP darker than ?_ sec. at ??/16

    It saddens me to read comments that seem to say that there’s too much thinking involved with the techniques explained by Mr. Randall in this article. I own and use PS, LR, & other software for ppc on my images but I no longer have to use them as much to correct an exposure, or even to prepare and print an image as I saw it. Learning fundementals of image capture under different conditions yields a greater likelihood of ultimately capturing the desired image for presentation. Just as some images can only be properly realized using ppc software, there are images that today’s software has no hope of getting right. I believe work such as Ansel Adams’ could be approximated, not duplicated, strictly using software, without using proper capture fundamentals. The zone system is a tool – just like software, for realizing images. It is important, I think, for a photographer to become as versed and adept in all aspects of capture and ppc as possible; if one is serious about the craft.

    I find that this article is very interesting. If all it takes is to reference the midtone and highlights and open up the aperture. Then why would I sit in front of the computer for 15 minutes when I can get the result that I want IN-camera. I agree with Mr.Phil and with Glenn Randall (the author). Learn your craft. And the art will follow. Too many people come out of photography school with no concept of shutter-speed/aperture relationships and how ISO affects it.

    I too have concluded that my Canon 5D Mark II is limited to +/- 2 stops of useful, natural looking detail before highlights are washed out & shadows block up or look purple with noise.

    Despite all the fabulous digital progress, this very nice camera is still several stops short of the best film technology.

    My own approach is to never clip the highlights in any scene & suffer block out shadows when the dynamic range is exceeded since dark/black shadows are more natural looking that featureless white parts of a scene.

    The article was interesting but I don’t understand why there was no discussion of using the camera’s histogram to assess exposure. Take a shot, analyze it and take another. This usually works with landscape photography where there is no movement. If there is movement and you need to get a perfect exposure rapidly, there is often no time for the zone system analysis. Then, with modern cameras, you can set up automatic bracketing and shoot three quick shots which will give you the option of picking the best exposure or using HDR if you prefer that. In you don’t use HDR, you can simply use the basic Exposure adjustment on a RAW file with one of the bracketed shots. In digital, we don’t need to worry about a slide that cannot be adjusted.

    HDR looks fake to a trained professional photographer and editor. Add to the fact that most outdoor and nature magazines do not accept them because of that and when a professional submits them they then get labeled. Outdoor Photographer only accepts them when are labeled so they can let the reader know when they are looking at HDR! I can spot them almost everytime and when I can’t I can not understand when the person shot it in the first time since a well exposed single image can do the same without the wasted time to create one. HDR is fine for prints and those magazines that do not care about realism.

    It’s always best to start with the best possible image. Then, use hdr to bring out the best of all exposures. Ansel Adams did the same thing in the dark room…he believed 1/2 of his photography was in the printing and would be the first to embrace hdr. On the issue of moving subjects: when you’re stopped down to f11 for sharpness across the scene, subject movement will always be an issue. That’s when the discipline of waiting comes into play.

    Mr Randall’s article is just as essential as the thousands that preceded, discussing the same old topic, appropriate exposure as compared to the dynamic rage of the scene and that of film, and now of our incredibly sophisticated camera sensors. Nothing has changed and one cannot dismiss the so called ‘old school’ photographic techniques just because something came along seemingly trying to make our picture making efforts easier. One must consider articles the likes of Mr. Randall’s as an essential part of ‘growing up’ as a photographic artist. It succinctly summarizes the essentials of exposure as related to today’s cameras. I would recommend it as a standby resource, until you are as comfortable with the procedure as you are driving your trusty standard vehicle, as ‘tdsutter’ suggests. Keep on reading and practicing, and don’t settle for the ‘quick fix’.

    I also shoot many HDR photos but as stated in many comments above, it’s no excuse not to learn everything you can cram into your brain about your gear. Maybe it’s just the nerd in me but I love learning new techniques for using DSLR. I also have used this metering method for outside portraiture and it gives me more time to shoot when I do not have to do much post production.

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