By Ctein
Got your attention, didn't I?
Unless you don't know what I'm talking about. Lucky you.
For those who haven't been force-fed this bit of dubious dogma, "Expose to the right" is a rule that asserts that to get the best quality in your digital photographs, you should push your exposure as far to the high side (the right side of the histogram) as you can without clipping the highlights.
Once upon a time, this rule made a certain amount of sense, although not as much as its proponents ever claimed. Once upon a time, digital cameras were pretty noisy beasts, and suppressing that image noise was one of the more important ways to improve image quality. Increasing exposure increases the number of photons counted, which improves accounting statistics. Hence, reduced noise. If you can do this without clipping highlights, it's a win.
These days, noise is really not a big source of image quality loss, unless you're that particular kind of photo-fetishist (see "The Photo-Fetishistic League"). Cameras and sensors are so much better. Clipped highlights, as Mike and I discussed last week, haven't gone away. It's still a big issue when trying to get real quality in a digital photograph.
The thing is, digital behaves like slide film—slide film with a really, really sharp toe. The toe of the film curve is low in contrast, so there is not a hugely abrupt transition from no detail in the highlights to a little detail. Digital is abrupt. When you hit the wall, you know you've hit the wall.
The worst thing you could do with a slide film was to blow out the highlights. Many professionals routinely underexposed their slide film to avoid this. Pictorially, the results weren't as great, but you could fix that in printing and reproduction. You couldn't fix blown highlights.
In theory, you can still use the dubious right-hand rule. Just be careful to never blow out any pixels. In practice, much easier said than done. Histograms and camera-back displays are only an approximation of what's actually in the file. Even when they aren't, highlights are frequently small enough regions of the photograph that they don't contain a statistically significant number of pixels. You may not even notice them in a histogram, and on that little screen on the back of the camera that shows you maybe one pixel in ten, highlight warnings may not show.
1. The original photograph was underexposed by more than a stop to maximize the amount of highlight detail it held. A straight conversion in ACR, unsurprisingly, looks quite underexposed.
2. For the sake of clarity in illustration, I've converted illustration 1 to black-and-white in ACR so that color doesn't distract from the important discussion.
Unless you're sure you're dealing with a low contrast subject, pushing your exposure to the high side makes it likely you'll blow highlights. If you're trying to improve your odds of getting a good exposure, pulling away from the right is a much smarter thing to do. If you know your subject is really high in contrast, pull far, far away from the right. Keep those highlights under control and let the shadows go where they may.
Of course, if you don't take steps to correct the tonal placement when you process your file, it'll look lousy. It'll be very dark, with middle-tones that look more like charcoal. Not a pretty sight. Kind of like illustrations 1 and 2.
This photograph was substantially underexposed to ensure that the highlights didn't blow out. Illustration 2 is just a desaturated version of illustration 1, because it's easier to see what I'm talking about without the confounding effects of color. Don't think this is just about black-and-white, though; blown out highlights are at least as annoying in a color photograph. Nighttime scenes like the one shown are especially high in contrast, which is why I'm using this as an illustration for the article, but the rules apply equally to normal daytime photography. This is not a special technique to be used in unusual circumstances; it should be your normal way of working.
3. Even with underexposure, there are some blown highlights, shown in red.
Even with this underexposure, there are some blown-out highlights. Illustration 3 is a screenshot from ACR with the highlight warning (bright red) turned on. In a really contrasty scene or one with glaring or specular highlights, something is likely to blow out, no matter what the exposure range of your film or sensor it is. Underexposing minimizes but doesn't always eliminate that. We can deal.
4. The straight-line curve and the accompanying histogram on the left are from the default conversion in ACR. The curve and histogram on the right are my custom conversion designed to compensate for the underexposure in illustration 1 and 2.
The left side of figure 4 shows the characteristic curve in ACR that I used to get illustrations 1 and 2. It's my standard default ACR setting. Below it is a histogram for illustration 2. Notice how everything is piled up near the shadow end, far from the right side. Overall, way too dark. To fix that, I used a curve setting like that on the right side of figure 4. It produces the histogram below that curve, and illustration 5 shows what the picture looks like with that curve applied.
5. The same photograph as converted with a custom curve. Good tonality, good shadow separation, and no harsh highlight transitions.
That curve has three major benefits. Obviously, it restores the overall tonality of the photograph to something normal without adding more blown highlights. Next, it produces good contrast and separation in the shadows, where it is hard for the human eye to see tonal differences. We see shadow differentiation in prints poorly, so some extra contrast down there is a good thing.
The third benefit, and it's a huge one, is the rolloff in the shoulder of the curve, lowering highlight contrast. That means that what blown highlights are left don't jump out as harsh white blotches; the highlight detail just gradually fades out into white, the same way it does in a well-made darkroom print.
If you really can't stand the idea of any additional noise in your photographs, run a noise reduction plug-in on the image. You won't need a very strong setting; the noise difference between a normally exposed and an underexposed digital photograph is not all that great. Just a whisper of noise reduction will take the noise level down to where it would have been if you'd exposed normally or even to the right.
Just, whatever you do, don't expose to the right unless you're absolutely positive there are no highlights to get blown. It was a questionable rule to begin with; these days I call it downright dangerous.
Ctein
Ctein, who is a high-end custom printer among other things, writes a regular weekly column on TOP that appears on Wednesdays.
Editor's Note: Several readers have referenced an article I was not aware of on The Luminous-Landscape about ETTR. That article was published in 2003, when, as Ctein acknowledges, ETTR made more practical sense. From 2003 to 2011 has been a very long time in this particular stretch of the history of photographic technology.
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Original contents copyright 2011 by Michael C. Johnston and/or the bylined author. All Rights Reserved.
Featured Comment by Joe: "In my opinion, digital photographers have gotten way too used to using Photoshop to bring out detail in the shadows.
"A few years ago I visited a wonderful exhibition in Tucson, at the Center for Creative Photography, of some of the great New York City street photographers, mostly vintage prints from the mid 20th Century. And it turned out to be an eye-opening experience for me, because it reminded me that photo printers didn't used to fear the shadows. There was lots of detail in the highlights, but those blacks were black. Whole swaths of those prints were completely without detail. And they were just stunningly gorgeous.
"That was the end of my expose-to-the-right period."
Featured Comment by Niels Geuze: "I have learned to expose the subject right."
Featured Comment by Bill Pierce: ""I used to feel terribly guilty not exposing to the right, just exposing the same way I did shooting an ungodly amount of slide film over the years. Thanks to Ctein my sin has been washed away and I feel whole again (and I’m often using a handheld incident meter that favors exposure for the highlights)."
Pierce, as he's known to his friends, wrote the "Nuts and Bolts" column at The Digital Journalist from 2006 to 2010. —Ed.
. Lest anyone get distracted by my blathering, let me be clear: this is the best small digicam on the market—Number One amongst the numberless legions—and a refresh/upgrade without changing the S95's essential character is all that's needed or wanted.
. Except Canon used that exact name 11 years ago for the U.S. version of the IXUS. So then they can't...? They wouldn't...? Wrong, they did. The new Canon is the third coming of the S90...and also the second coming of the S100.
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by the talented Jennifer Michael Hecht (she's also a poet) or the delightfully entertaining Ecce Homo! by the French materialist Baron d'Holbach. And I'm actually not a big fan of "The New Atheism"—Hitchens, Dawkins et alia—which as a rule I find tendentious and ponderous as well as partially if not largely irrelevant. For believers, I don't think logic enters into it, so logical refutations are sort of talking past the point.
. Not only are they Englished quite differently, but the translators in either case had quite different sources from which to work. Then there are commentaries for both the credulous and the skeptical which further illumine the experience. (The one I wanted to recommend I can't find...I wonder if I loaned it to someone.)
arrived here at TOP World Headquarters (a.k.a. my house) yesterday. It's a lovely little thing, seeming somehow tinier than the 40mm pancake because it's so much narrower, even though of course it's longer. The silent autofocus is almost disconcerting at first, if you're not used to it, but fits the lens's premium/luxe gestalt. The lens is at least so small and light that it will be a burden to no one's camera bag to carry it.
. Why? Well, because that's the one I got first and have been able to put through its paces. You'll get the other two reviews by the end of the year, I promise.
