'Expose to the Right' is a Bunch of Bull

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.

Comments

[CN]

Finally some common sense written about ETTR. The thing about rules like ETTR is that they do not necessarily apply in all situations. A good understanding of any general rule and your equipment is mandatory to choosing how you are going to expose and process an image – shock, horror!

Personally, I never understood the obsession with always retaining shadow and highlight detail. Why can't shadows be black or highlights be pure white? Because it's "common practice"? How about exercising some aesthetic and technical judgement?

A good image is not always dependent on having full tonal range. Conversely, a bad image is not necessarily one that lacks tonal separation. The aesthetic and emotional quality of an image is made up of more than just tonal range, noise and/or grain. Daido Moriyama's work is a perfect example of this.

ETTR has progressed from being a useful rule of thumb to dogma.

[Semilog]

"The darkest stop = 32 tonal values"

That would be correct if the accounting started at zero. However, because there is a noise floor, and for other reasons, in essentially all digital cameras there is always an "offset" at the A/D converter*, such that there are a few bits that fall below the noise floor. The offset is introduced in part to prevent the under-quantization that Mr. Pedde and others on this thread have shown some concern about. Noise (read noise, and under some circumstances shot noise) is a concern. Under-quantization is not. People who say that do not understand that the EE's who design sensors are smarter than they realize. The EE's recognized these problems decades ago, and solved them.

*Note that except for highly specialized scientific cameras, "digital" cameras are actually analog devices, accumulating charge (potential) that is first amplified by one or more analog amplifiers. Thes amplified analog voltage is then quantized by an A/D converter. Single electrons (or holes) are not quantified.

[ctein]

Dear Folks,

Data is not information. "Maximizing data" does not mean you are maximizing the quality of your photos.

Being concerned with "maximizing data" is one of those wonderful bits of physical theory that has very little to do with real photographic image quality.

pax / Ctein

[John H. Maw]

Let's not get too bound up with rules (Rules are for people who can't see. If you can see, why would you need rules?) Sometimes you want to blow the highlights because you don't want or need the detail.

If you want a full tone print you will need to have some white and some black in it anyway (otherwise it isn't full tone).

[ctein]

Dear CN,

I don't think that's entirely fair. I think most people who even heard of ETTR treat it as a rule of thumb. Oh sure, there are a few dogmatists out there. We've got a few comments here from people who think we're talking about hard and fast rules (any time you see someone say something like, "Well, yes, but there will be cases when..." you know they don't understand what "rule of thumb" means).

But, by and large, I don't see that as a bigger problem here than in any other part of photography. I'm arguing that it's a very poor rule of thumb, that's all. Not taking on the dogma issue (although that might be a good future column topic).

Blocked shadows are rarely objectionable in practice. Annoying from the practioner's side, who always knows what they started with in the scene but had to settle for in the photograph, but they rarely prevent attractive art or are an evident flaw to the viewer.

For the reasons Mike and I discussed in the "B&W sensor" column, blown highlights tend to be much more objectionable. Not always-- rules of thumb, remember-- but often-to-usual. It's not merely their presence, it's that they're abrupt holes in the middle of the composition. They may be the single thing that skilled practioners hate the most about digital photography.

Anyway, I'm still just producing a rule of thumb, not a dogma. As many people have said, what you really want to be able to do is get the exposure right. (For whatever that means for you.) Unfortunately, that's not simple, in total -- it's a complex and difficult subject. Rules of thumb are valuable practical tools.

pax / Ctein

[David Luttmann]

Nice to see that even well known photographers like yourself can be wrong.

[Gerry Winterbourne]

This seems to be a departure from your usual style; it seems to be 1.1/2 of two separate topics.

As you point out, actually achieving a correct ETTR exposure is tricky given the capabilities of current cameras. But you usually give advice on how to achieve difficult things rather than saying "let's forget about them". As I understand ETTR - exposing TO the right, not PAST the right - it is identical to exposing for the highlights. So the first topic (about 1/2 of which you have written) covers these things.

The second topic is about the use of tone curves to deal with any shot whose exposure (necessarily to protect highlights or for any other reason) looks dark. In this one you have, as usual, given a clear exposition.

It just seems a pity to me that you felt the need for the first part to get to the second.

[Rob]

One of the motivating forces for some who practice ETTR is a dread of dark shadows. Absence of shadow detail to them is a cardinal sin. You frequently encounter this kind of thinking in photo critique forums, and I have no doubt that it is also what motivates much of the hideous HDR photography that is so popular these days. (I'm not saying that all HDR is hideous.)

I write this having just browsed through a book of photos by Mario Giacomelli. Now, there was a man who was not afraid of black shadows, but rather saw them as strong aesthetic elements in his photography. Others might take a lesson from him and learn to embrace the darkness.

[ctein]

Dear David,

You flatter me; I do wish I were well-known enough to be considered "well known." But thanks, it's nice to hear.

I've been wrong more than once in the past; you probably missed it because it's not all that common.[ahem]

I try to thank people when they correct an error, because I like to learn things. I'd rather not be wrong.

Happily, this is not one of those occasions.

pax / Ctein

[CN]

Ctein

I guess I should qualify my final sentence as:

"ETTR has progressed from being a useful rule of thumb to dogma" by it's proponents, as experienced by me.

In my experience, the dogmatists, like the fetishists, are always the most vocal (rabid?) on a particular subject. I have had some personal encounters with ETTR dogmatists, so I guess my comment betrayed my own particular bias.

I agree that digital highlights are less likely to be aesthetically pleasing, but as you noted in your article, this is due to the characteristics of the digital medium. The few photographers that I can recall off the top of my head who have used areas of white in their images (e.g. Daido Moriyama, Rinko Kawauchi, Trent Parke) all use(d?) film.

More generally, I also wonder if it there is a discomfort in Western culture with the concept of having holes (as you put it) – i.e. emptiness – in a composition. (Again, betraying my own personal background and interests.)

An article by you on dogma would be interesting, especially as to how it may relate to the fetishists.

Regards
CN

[Kelvin]

http://theonlinephotographer.typepad.com/.a/6a00df351e888f8834015436021b2e970c-popup

Looks like Friedlander exposed to the right :)

[ctein]

Dear Gerry,

I think you misunderstood the impetus for this article. Go back and read the discussion that Mike and I had about B&W sensors to get the backstory and the context.

This is not a gratuitous dig at ETTR on the way to some other topic/technique.

~~~~~~~~

Dear CN,

Excellent points. Dogmatists are an inevitable part of our universe. I tend to ignore them (except when skewering them en masse) because they don't represent the merits of an idea or technique. It's unfair to us to reject potentially useful methods because they're championed by fanatics.

I don't have any kind of opinion on your very intriguing idea that our collective dislike of abrupt holes is part of a larger aesthetic. It's worthy of serious thought.

As Mike and I talked about, and I explained in this column, there's no objection to true whites (or blacks) in a print anywhere in our discussion. It's the slam-into-the-brick-wall effect which offends, and WHY it offends is a fine question.

pax / Ctein

pax / Ctein

[Lars Clausen]

Hi Ctein,

Thank you for a very nice article on how to do ETTR.

Despite your titling (and you're probably aware of this), what you're carefully explaining in this article *is* ETTR, it's just that "ETTR" is a horrible, misleading, confusing name. ETTR has always been about exposing as far to the right as you can *without clipping highlights* - in high-contrast situations, this is "exposing for highlights", but in low-contrast, you can get a bit of extra quality by overexposing.

ETTR is emphatically not about setting your camera to +1 exposure. In fact, even getting close to the highlights without clipping can twist the colors unpleasantly. But saying that ETTR is bull, is... bull. It just heavily misunderstood and needs a name that people can understand. Like, say, "expose for the highlights". Or "expose to just before blow-out".

And to various commenters: It has nothing to do with "rules" like the golden ratio. It's a technical recommendation just like "use a tripod" or "keep your glass clean". There are technical limits to when it applies - I wouldn't use it in street photography, as I would not be able to adjust the exposure fast enough to ensure lack of clipping. But it does not tell you how to compose your shot in any way, just how to get the best tonal values possible when the situation allows it.

[CN]

Ctein

Regarding the aesthetic quality of digital highlights, I have recently begun noticing a "crunchiness" to highlights in editorial images (whether in newspapers or higher-end magazines)*. This may or may not be related to improper sharpening and/or digital processing. I wonder also if the delivery of files in JPEG format may be compounding the problem. In effect, perhaps the inherent weaknesses of the digital process is being amplified by a combination of editorial expediency and/or lousy workflow practice.

Whether this also applies to exhibition/fine-art work is another matter, but I have not come across any glaring examples of such, and given the nature of such work, I don't expect to.

*Not to imply that newspapers are low-end, but the nature of newsprint stock doesn't exactly lend itself to high-quality image reproduction.

[Feel free not to post what's below, as it's very off-topic.]

Going even more off-topic, I mentioned the larger aesthetic considerations purely as a spur-of-the-moment thought in the context of my interest in graphic design and Buddhist art, especially with regard to constructivist and modernist-era graphic design and Buddhist ink painting.

Photography hasn't seemed to me to wholeheartedly embrace the concept of white/empty space. (As much as I love Irving Penn and Richard Avedon's personal work, I don't generally consider that the backgrounds in still-life and fashion photography count.)

Regards
CN

[David Luttmann]

Unfortunately, this is one of those occasions Ctein. I have compared the shadows in B&W conversions on prints of 16x20 to 32x40 in size from a Canon 7D and Pentax K20D. Exposing to the right rather than allowing the metter to do its thing resulted in lower shadow noise. If you were correct, there would be no difference. As there was a difference, you can add it to those rare occasions when you were incorrect.

No disrespect intended....but I trust my eyes and what I see over someone who tries to convince me that the difference that I find obvious isn't there.

Sorry, and all the best.

[stacymarie]

You can't compare film to digital sensors. It's just not a fair comparison. Film and digital see the light in different ways. With film, you expose for the shadows. With Digital, you expose for the highlights. There is more detail in the shadows (for digital) when you expose to the right.

Sure, as sensors get better there is a possibility that this may no longer be the case, but many of us are using older equipment and must expose to the right in order to make sure we have detail in our shadows.

It's really frustrating to hear this from you.

[Bryan]

I always thought that ETTR was exactly what you're advocating here. You expose the image as far to the right as possible without clipping the highlights. By doing so, you get the most information possible in the highlights and the shadows. It might be hard to judge in the field, but that doesn't make the technique invalid.

On difficult shots such as this one, it pays to bracket.

[Bob Fisher]

Didn't read all the comments so not sure if anyone already mentioned this. Even if so, it bears repeating.

There are some flaws in this analysis of ETTR. There are two conditions that need to be kept in mind when using ETTR.

First, the exposure is pushed as far to the right as possible without blowing out any hightlights. Some will say without blowing non-specular highlights but that's wrong. It's push to the right without any clipping. Period.

The second, and more important aspect of ETTR is that the scene/subject contrast or dynamic range has to fit within the range of the sensor. So if you're shooting something with a 12 stop range using a camera with an 8 stop sensor, you're hooped as far as ETTR is concerned.

Ctein seems to be considering the first but not the second. The scene in question is high contrast and outside the range of the sensor. For those situations you have to make a decision. Are you going to have blown highlights, blocked shadows or are you going to use some other method (exposure blending/HDR) to get what you want?

To be clear, I'm not one of those ETTR zealots. I rail against them as loudly as anyone. But even with today's low noise, improved DRange sensors, ETTR can still have a place provided it's used properly.

All the falderal about the in camera histo being based on a JPEG is just so much noise. With a modicum of testing, it can be pretty easily figured out how the in camera histo is showing the brightness range and how much head room there is to push to the right.

[tony harrison]

if you are shooting at 1600 and over expose by one stop to the right, to have less noise,you also halve the shutter speed. your effectivly exposing at 800, in which case you would have less noise anyway, so why not just use 800. with a balanced exposure. if anyone can tell me something I am missing please reply. tony harrison.