If you’ve been taking digital photographs for any length of time, you have probably heard the phrase “dynamic range.” It’s one of those phrases that other photographers use under the assumption that everyone knows what it means, even though most beginning photographers have at best a rudimentary understanding of it.
Dynamic range as it pertains to photography has something to do with light and something to do with camera technology, and understanding what those somethings are can really help you improve your photography, especially while you are in the learning stages. So why is it that no one has ever really told you what dynamic range is, and why you should care? Because it’s so fundamental that those old timers just assume its like breathing. Except of course that it’s not.
What is dynamic range and why is it important? Keep reading to find out.
Blown out to the max by Flickr user Jim Grey
Dynamic range is actually one of the most common lighting problems that a photographer is likely to encounter. It has to do with the difference between what your eye can see and what your camera can see. So really, it’s a problem with the technology, and the good news is that that technology gets better and better all the time. One day, dynamic range will likely no longer be a problem because all cameras will be capable of dealing with it. But today you need to be aware of dynamic range and have a good understanding about what your camera’s limitations are.
IMG_7515 (explore) by Flickr user snorski
Defined, dynamic range is basically just the difference in tones between black and white. In certain lighting situations (such as high noon), there is so much difference between the blacks and the whites in the scene that your camera is simply not capable of capturing the complete range of tones between those two values. So what happens is you either get burned-out highlights that lack detail, or you get too-black shadows that also lack detail. That’s going to be a problem for you if you wanted to capture both the detail in a very bright sky as well as the detail in the darker foreground.
Dynamic range is measured in Exposure Value, or EV, otherwise known as “stops” (which is probably the more familiar term). Our eyes can see roughly the equivalent of 10 to 14 stops difference between white and black. Now, depending on who you ask this number could actually be as high as 24 stops or more, but since the human eye is always making adjustments whenever we look from one part of a scene to another, this is not really an accurate number to use when comparing our eyes to the average digital camera. If we keep our attention on one specific part of a scene, then the dynamic range of the human eye is closer to 10 to 14 stops. Still, that’s a lot better than the average point-and-shoot (which can only capture somewhere between five and seven stops of dynamic range) and marginally better than a good quality DSLR, which can capture somewhere between eight and 11 stops of dynamic range.
Now sometimes this matters and sometimes it doesn’t. Let’s say you’re shooting on an overcast day—there may be only three stops of dynamic range in any given overcast scene, just based on the fact that the clouds are filtering out most of the very bright light and bathing the scene with a soft, diffused light. So from a dynamic range perspective, it doesn’t really matter if you shoot that scene with your point-and-shoot or with your DSLR, because you’re not going to be losing any detail in the shadows or the highlights. Every modern camera can capture a scene that has only three stops of dynamic range.
If, on the other hand, you’re shooting a scene at noon on a very bright sunny day, you may have more than 12 stops of dynamic range in that scene, so even your very expensive DSLR may have trouble capturing a complete range of tones. When this happens, you end up with an image that has blown-out highlights or too-black shadows, and unless you take some evasive action you’re going to either have to choose to expose for shadow detail or for highlight detail.
So you really have to think about two separate things whenever you’re shooting a brightly lit scene—how much dynamic range is in the scene itself as well as how much dynamic range your camera is capable of capturing. Cameras that aren’t capable of much dynamic range may obscure details on both ends of the spectrum, while cameras that are capable of good dynamic range may capture a perfectly exposed image. So it really does help to have some understanding of how much dynamic range your camera is capable of.
How can I tell?
Most camera manufacturers don’t publish the dynamic range capabilities of specific camera models, or if they do, it’s not really part of their marketing (unless of course the capability is particularly excellent). After a while, you will get a good feeling for which scenes your camera will handle well and which scenes it’s going to have some trouble with, but in the meantime you can use your camera’s histogram to give you that information. When in doubt, shoot a test image and then look at the histogram for that shot (if you’re not sure how to do that with your camera, you may need to refer to your manual—some cameras have a setting you can enable that will show you the histogram when you review the image on your LCD, and others will even show you the histogram before you make the exposure). Look for “clipping” on either end of the histogram—this will show up as an abrupt end to the pixels on the highlight or shadow side of the chart, rather than a gradual tapering off towards the horizontal bottom of the chart. If you see clipping on either end or on both ends, you’ve got a dynamic range problem for that particular photo.
Sometimes it’s just a problem with the exposure itself—you may have under or overexposed the shot, for example, and a slight adjustment to the settings will fix the problem. But sometimes there isn’t anything you can do to the settings to change that clipping, and that’s when you’ve got a problem.
How to deal with dynamic range issues
Depending on what you’re shooting, there are a number of ways that you can handle dynamic range problems. The first and most obvious is to simply come back at a different time of day. During the “golden hour”, (the hour just after sunrise or just before sunset) there is actually less dynamic range overall because sunlight has more atmosphere to travel through before it reaches the surface of the Earth. So for the most part, scenes shot during this time of day are going to have less dynamic range—with a single exception. If you include the sky and the sun in your photograph (if your subject is the sunset or sunrise itself) you’ve now got a scene with very broad dynamic range, because the sun and sky have much greater brightness than the foreground.
If you’re shooting landscapes, simply shooting closer to the golden hour may not be enough to cope with the dynamic range problem because you’re still going to have too much difference between the brightness of the sky and the foreground. So you can either expose for the sky and let everything else in the frame become a silhouette, or you can use one of two techniques that can help you cope with the problem.
Molten Horizon by Flickr user ecstaticist
The first thing you can do is purchase a simple graduated neutral density filter (GND), which is a filter that is darker on one end and gradually transitions into clear on the other end. When you place the darker end of the GND over the sky and the clear end over the foreground, you’re actually bringing down the dynamic range to a point where your camera can capture the entire scene without losing detail in either the sky or the foreground. With a GND, you’ll get a rich, deeply textured sky and a well-exposed foreground—the best of both worlds. This tool can help you regardless of what time of day you shoot, at any time when there is a big difference between the brightness of the sky and the foreground.
Another thing you can do to cope with a dynamic range problem is to shoot in HDR. Now, you’ve probably seen over-the-top HDR images on Flickr or elsewhere on the web, and I’m not suggesting that you try to duplicate any of those images. HDR doesn’t have to look over-processed, it just has to capture detail in both the highlight and shadow areas of a scene.
The process for achieving this is relatively simple: you do need a tripod, because you’ll be making at least three different exposures of the same scene and you need them to line up correctly. Set your camera up on the tripod and take one shot at about a stop below where your meter thinks your settings should be, then take another at the exposure your meter thinks is correct, then make a third exposure at one stop above that reading. Ideally you want to be shooting in Raw, but you can also do this successfully in JPG.
Now you need to combine all three exposures into a single image, which is a lot simpler than it sounds. Depending on your post-processing software the technique varies a little, but in Photoshop you just go to File > Automate > Merge to HDR Pro and then you select all three exposures. The software will automatically merge the three images, though you will also get a selection of presets so you can choose how much processing you’d like to apply. If you’re going for a natural look, select a preset that doesn’t look over-processed but still gives you plenty of detail in the highlights and shadows.
HDR fireweed sunset by Flickr user Traylor Photography
If you’re shooting a human subject (or something else that moves), you can’t really shoot HDR because it’s too difficult to get three shots that line up perfectly. In a situation like this one you need to fill in those darker shadows, so that you’ll end up with less dynamic range overall. You can do this with fill flash (your pop-up flash will usually do a pretty good job) or you can use a reflector to bounce light into the shadows. Either option works very well for those midday portraits or even for smaller subjects like flowers that happen to be sitting in direct sunlight.
The dynamic range problem may go away one day as camera technology improves, but until then it’s still something you need to be thinking about all the time. Whenever you are in an outdoor lighting situation, think about how bright the scene is. Chances are if you feel like putting on a pair of sunglasses, you’re probably going to have to consider dynamic range when you take photos in that environment. A GND is a great investment if you shoot a lot of landscapes; if portraits are your thing, stash a set of reflectors in your camera bag. If you’re prepared for those high dynamic range situations, you won’t be disappointed when you look at your photos later on because you’ll be able to cope with those issues before you even press that shutter button.
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