Deal 9: Hacking Photography mega-deal
Exposing to the right (often refferred to as ETTR) is a technique that seems to polarise opinions across the internet so you can find plenty of examples of people supporting its use and an equal number of people claiming it adds no value. The principles of the technique however do hold value and are valid to consider when out taking images. As it is a technique that I regularly employ when photographing landscapes I wanted to share the reasoning behind it, and show an example of the benefit it can bring.
The term ‘expose to the right’ refers to the histogram associated with an image. Typically, for a shot to be well exposed, we are taught to aim for an even spread of tones across the histogram, peaking in the middle, and tapering off at the edges. When ‘exposing to the right’, the idea is to push the peak of the histogram as far to the right hand side as possible, i.e. overexpose the image, without clipping any highlights. The resulting file, when processed back to the correct exposure, will contain more tonal information and less noise in the shadow areas, maximising your image quality.
Let’s consider the CCD or CMOS sensors found in most digital cameras. Typical DSLR sensors can capture seven stops of dynamic range and produce 12-bit raw image files, capable of recording 4096 tonal levels in each red/green/blue channel. The ability to record such a large number of tones should guarantee smooth transitions between the tones within the resulting image, however it is not quite that simple.
Whilst you might think that each of the seven stops in the range of the sensor record an even number of tones throughout the dynamic range, you would be mistaken. F-stops are logarithmic in nature meaning that each stop records half of the light of the previous one. Practically, this means that the brightest stop records half of the possible number of tones, i.e. 2048, the second stop records half again, i.e. 1024, and so on until the seventh stop that records only 32 tonal levels. Therefore, if you underexpose an image and correct the exposure during in post processing, the tonal transitions in the darker areas will not be as smooth, and the risk of degrading your image quality is much higher. If you overexpose your image, by pushing the histogram to the right, you will capture much more tonal information that results in much better image quality when correcting the exposure in post processing.
The diagram below tries to illustrate the distribution of tones for each stop of the dynamic range of the sensor. The top image shows the seven different stops capturing different portions the dynamic range from the darkest through to the brightest tones, however the bottom diagram shows those stops but sizes them relative to the number of tonal levels that each stop captures. As you can see, number of tonal levels captured by the brighter stops is significant compared to the stops at the lower end of the dynamic range.
A tangible way of demonstrating the difference in the amount of tonal information recorded is to take two images of the same scene, one underexposed, one overexposed and compare the file sizes: the overexposed raw file will be larger that the underexposed shot as it contains more data.
Let’s look at an example. The image below shows two unprocessed shots taken within seconds of one another, with their associated histograms. The shot on the left is underexposed and the shot on the right is exposed so that the histogram is pushed up to the right hand side, as far as practically possible wihout losing any highlight detail.
During processing, the exposure of each shot can be adjusted to give what seem to be two identical images.
However, when you look in detail at a 100% crop of an area of each image, you can see a huge difference in the quality of the final image. The shot that was underexposed (i.e. exposed to the left) shows much less smooth transitions between tones and much more noise in the darker areas than the image that was exposed to the right.
Images that have been exposed to the right will need some additional post processing to correct the exposure, but as you can see, a bit of extra thought when determining your exposure and some extra steps to correct it during post processing can result in image files with smoother tonal transitions and reduced image noise.
It is not a technique that is universally applicable to all types of photography, as there is a risk of clipping highlights if care is not taken when exposing your image. Exposing to the right is most suited to when photographing in a controlled environment, for example, when shooting landscapes, using graduated filters to ensure that all highlights are contained within the dynamic range of the sensor. The last thing you want to do is to lose highlight detail when trying to maximise your image quality.
So give it a go, take two images at different exposures (one exposed normally, one exposed to the right) and see if you can see a difference. Understanding the performance of your individual sensor in such a way is a step further to knowing how to get the most out of your camera.
May 13, 2013 07:19 pm
Really interesting article - thanks....
I usually do expose more to the right but it was more of a gut feeling that the photos would be recovered in RAW now reading this article I can see why..
I have had photos that I accidentally exposed way to right and then seen how they 'magically' look perfect when I press the auto button on photoshop RAW
March 23, 2013 08:54 am
Yeah, great article and has got me thinking I need to get out and practice! Ha :)
January 18, 2013 02:54 am
Well interesting, but shooting to the left let you take the picture with a little more speed ex 1/60 instead of 1/30 or even 1/15 and this is a good thing when shooting with limited light and no support for the camera.
December 28, 2012 06:12 pm
Thanks a lot for give me right info. This is very necessary for every photographer.
December 19, 2012 05:10 pm
I like how you set about to prove the superiority of ETTR but I believe your selection of data points is flawed. All you have proven is that with ETTR you can achieve a well exposed image in post processing - with extra work. By comparing against an undeexposed image, you have not proven that it is a superior method to properly exposing to begin with. A fair test would have been a comparison between a proper exposure and an ETTR exposure. It seems to me that when you correct the ettr image, it will necessarily have to shed the extra detail when each colour is resolved back to its proper zone. I will definitely attempt this test on my own, but I remain skeptical in the meantime.
December 17, 2012 06:44 am
@Dan Cassat: I definitely agree that ETTR is a valid tool for pulling extra bits of info from an image if needed. If a scene is low enough in contrast that you can safely overexpose, I say go for it. However, it seems that (at least with my cameras) specular highlights blow out in an ugly fashion, as opposed to a smooth transition to white in a proper exposure. I feel like this presents a lot of problems for any scene with a typical exposure range, such as bright clouds in a landscape, streetlights/headlights, reflections off of windows and metal, etc. This seems to limit ETTR's practical application for many types of photography (though when a scene calls for it, I wouldn't hesitate to use it).
@Greg Moffatt: Adjusting either the whites or highlights in Lightroom will bring down the upper-most section of the histogram without affecting the shadows. This makes for a strange looking, midtone-filled image that doesn't match the properly exposed version at all. On the other hand, adjusting the exposure slider centers the entire histogram and matches the other image almost exactly. That's typically how ETTR works (in my understanding); you want to initially overexpose and then bring the entire exposure range down so that it's appropriate to the scene.
Regarding the ETTR test picture, it was exposed about 1.5 stops above the black-clipping point (there was a good deal of empty space on the left side of the histogram). The properly exposed companion image used in the comparison had no black clipping either, though the histogram reaches all the way to the far left.
Similarly, the highlights were initially bunched up on the right-hand side of the ETTR version (prior to adjusting -1.4 exposure), though the only thing that was clipping were specular highlights (and they were also clipping in the "properly exposed" image as well).
December 17, 2012 03:47 am
jon, I looked at your test pictures, and notice that you overexposed the test image by +1.4 and then used Lightroom to reduce the exposure by -1.4. Now unless the histogram was well away from the darkpoint, shouldn't you have just adjusted the whitepoint in Lightroom?
December 17, 2012 03:11 am
I have an additional note directed to Jon's response above and to those others that are worried about the highlights being overexposed. Since I use and test my shots daily with this technique, I really understand the benefits and consequences of its use.
1. You likely have headroom that you are not using (because the camera is over protecting the highlights), therefore optimizing the exposure using ETTR allows more room to pull the shadows up from the bottom.
2. This technique is not for everyone. You must be someone who cares about pulling the last goodness from your images and spending a little time understanding the difference between reality and what the camera thinks the proper exposure is.
3. In order to KNOW that you are not loosing image data from the edges of your histogram you MUST view your images with a tool that looks at the actual RAW file without modifying it in anyway.
4. Once you get used to the DIFFERENCE between the camera's version of proper exposure by using above tool, you will compensate and have the ability to correctly expose your images without guessing.
If you wish to look at your RAW data without modification (like what Lightroom might do to them) use a tool like RAW Digger (which is a free download). It will open your eyes to what is REALLY happening to your exposure.
If you have questions about how I use this technique, contact me @ firstname.lastname@example.org and I will direct you to the procedure and resources that I use.
December 17, 2012 02:12 am
In theory, ETTR is absolutely correct. In practice, to slightly over/underexpose depends on the camera the one uses.
December 16, 2012 01:49 am
Excellent update to the exposure process. I've always been an "expose for the highlights" ( or ETTL) kind of guy. That was from the days of shooting film. I can certainly see the benefits of this new process (ETTR) of exposing for the shadows, especially as it relates to digital imaging (and not film). I will pass along to my students. Excellent. Thanx again. . . bgs.
December 15, 2012 07:16 pm
This article made me a bit curious whether I could see a difference using ETTR with the Panasonic GH2 (which has a slightly noisy base ISO). Turns out there are some benefits, but also serious drawbacks to ETTR. Test images here: http://jonbaker.smugmug.com/Other/ETTR/
For all the pixel-peeping I did in my tests, I couldn't see any additional tonal information in the darkest shadows of the ETTR version (exposed +1.4 stops). Not saying it's not there, but I couldn't see it once adjusted to the correct exposure and compared side-by-side, nor could anyone I showed the images to. There was certainly less noise, even in the midtones, but that difference went away almost completely by adding a touch of noise reduction to the "properly exposed" image.
Specular highlights would blow out in an abrupt and unrecoverable fashion with ETTR. This may or may not be important in a given image (same with the extra shadow detail), but it's something to keep in mind.
So, there you have it. The moral of the story is: don't underexpose, and don't blow out highlights, and you should be fine. There doesn't seem to be much real debate about this anyway; as near as I can tell, the two camps say something like this:
ETTR: "Expose to the right as far as possible while protecting important highlights."
ETTL: "Expose to the left as far as necessary to protect important highlights."
December 15, 2012 02:13 am
Very confusing for me to comprehend.
I don't know how to pp or edit.
December 15, 2012 02:11 am
Looked as if the underexposed landscape was pretty close to clipping shadow, not mentioned in the article emphasizing detail at the light end. Bottom left of the crop suggests that may be slightly so. On that basis the correction labeled ETTR could be just a correction to optimize available information for the particular shot rather than a grand philosophy of light.
December 15, 2012 12:21 am
Excellent article! Very informative and well written. Thank you.
December 14, 2012 11:00 pm
I agree it's worth understanding the role of the histogram, and it indeed can come in handy. For instance, on blindingly bright days, I often can't judge the exposure of the image by looking at it on the back of my camera. Even if I can only see the histogram's spread, I can usually tell if the image will be ok later. That said, I prefer underexposed images to over-exposed, so I tend to go the other way !
December 14, 2012 08:21 pm
If I may respond to Ian C, the profesional portraitist: I think your primary subjects for the ETTR scheme will be the very dark-skinned, the very dark-haired, and those in very dark outfits. Your risk will be the loss of detail in white clothing or bright backgrounds, plus the highlights of the eyes and wet teeth/lips. You'll be able to pull some wonderful texture from clothing and hair that might have been nearly lost during normal exposure, but will risk blown highlights. It's something you'll have to run some controlled tests of before risking a whole shoot on setting your EC+1.
December 14, 2012 03:36 pm
Quick Question. I pretty much always meter plus one because I don't like middle grey. Is this the same thing or am I thinking of ETTR incorrectly. Thanks
December 14, 2012 02:49 pm
Well witten article and accurate. The key is, and you said it, is to expose to the right without clipping highlights. The fact that there are more tonal levels to the right is a scientific fact and one cannot argue against . Some photographer once said that noise is the result of incorrect exposure. Noise is always prone to hurt you in the shadow areas, rather than the midtones and highlights. I started using this technique when bracketing, and plain, even surfaces, like skies show much less noise when combining the images in Photomatix. The key, is however, not to "overexpose" too much...
December 14, 2012 12:08 pm
A note to those who care to try to use ETTR:
There are products that will show you the EXACT exposure of your RAW files. Looking at your images in such a program allows you to see just how much of your image data is lost at either end of the histogram. It may be necessary for you use such a utility to get a 'feel' for the way your histogram relates to the real data. Since the histogram is not based on RAW data but rather a .JPG rendering, the histogram is just an approximation. REPEAT, your histogram is just an approximation!! if you wish to truly maximize your exposure you must understand exactly what the exposure is.
ETTR requires some knowledge about how accurate your camera's histogram is to the real data.
If you are interested in exploring this further you can download one such product called RAWDIGGER for free, highly recommended. I am not affiliated with this company in any way.
December 14, 2012 06:32 am
@david - I imagine that if you shoot at ISO3200 and ETTR, when you correct the exposure during post processing, you would end up with a very similar image quality to the correctly exposed ISO1600 image - I imagine any gains you would get in image quality from ETTR, would be offset by the increase in ISO. Though, that is speaking from using my camera, which is not reknowned for its high ISO performance!. As bruno says, the only person who can know is you if/when you try it out. It's definitely an experiment worth trying though.
@tiberman Typically, when shooting landscapes, I will shoot in aperture priority mode, and I will increase the exposure using exposure compensation. As I am shooting at a defined aperture, with a set ISO, the result is a decreased shutter speed, to allow more light in. Hope that helps, good luck with the book!
December 14, 2012 06:07 am
Elliot - Your article is interesting for a beginner like me. Could please tell me, how, for the illustrated shots, did you 'over expose'? By decreasing shutter speed or through exposure compensation? I have a Nikon D7000, and am presently working on a number of landscapes for my book.
And warm regards from Mauritius
Tiberman Sajiwan Ramyead
December 14, 2012 05:15 am
Great article! Nice to see some analyses instead of just opinions.
I will try this for myself.
I agree with Blak however. In the example picture, I cannot judge whether the 100% crops differ because of the advantages of ETTR or that the left one is worse only because it had to be compensated more than the one on the right (in post production).
This makes the example unsuitable for proving your point. Even if you had good reasons to expose the way you did (to prevent clipping in the sky).
What I want to try is to take one correct exposure and one that is "exposed to the right", and than reduce the ETTR version to the correct exposure in post.
If your analysis is correct, the one comming from the ETTR version should have better tonal definition.
When succesful, meet the new member of the ETTR-posse.
December 14, 2012 05:07 am
@david - I'm not an expert, but I know as a fact that every camera (or rather every CCD) responds differently to the ISO setting, so your question is absolutely legitimate but the only one who can answers it is you (or someone else with your exact camera model): first occasion, try experiment what's best, and then.... write an article for dPS :)
@Elliot - thanks mate, now I really understand why ETTR exists: already used it sometimes, but never fully got why it worked.... :D
December 14, 2012 04:54 am
A really good artical, there are many ways of expressiong signal to noise ratio and this is a good one. I also agree with the forum comments on histogram "shape". I think that the trick is to use both the histogram and the "winking" highlight warning indication. You can see if you have gone too far when stuff you are interested in winks at you :-)
Another trick, good for good landscape clouds is to use a highlight as a keytone. Set to spot meter. Fill the spot with the brightest tone that you are interested in. Set the meter to show an over exposure of about 2.3 stops or so (best done on manual). Reframe and shoot.
Interesting comment Patrik, I use one stop in bright sun. In the "old" days when using slide film I would set the ASA one stop faster.
The process is "measure the light" then "estimate the exposure". The camera meter does both but it estimates assuming an "average scene". So the photographer must estimate the "exposure difference from average" required and use the bias. For average metering that is.
December 14, 2012 04:26 am
Elliot, thanks for the article and the clear technical explanation. When I shoot in low-light situations without a flash, I’m often conflicted about whether to shoot a “correct” exposure at ISO 1600 or ETTR at ISO 3200. (This is assuming I can’t slow down the shutter speed because the subject is moving and I’m already at the widest aperture.) Theoretically I should get better results by ETTR and bringing down the exposure in post, but it would be great if someone could confirm that available-light shooters in the field are actually doing this.
Are there other factors that come into play if I push the ISO? For example, will I lose fine detail due to noise reduction?
December 14, 2012 04:20 am
Shooting RAW allows recovering of an additional 1-2 stops of highlights if you know how to process the image correctly. So even on the camera histogram you can clip a little bit...
December 14, 2012 04:14 am
I ETTR, but newbies should know that this is a technique, primarily for those that shoot in Raw, or at least post-process their out-of-camera jpegs. The jpeg will be overexposed without post-processing. Also, turn on your highlight warning "blinkies" in your preview screen and also show the histogram in your camera's preview screen. With those warnings, you will not blow out important highlights. I often chose to leave unimportant highlights blown out, if I think that pulling up shadow detail will be more important to the image.
December 14, 2012 04:10 am
Interesting point, as most people would underexposed in harsh light so as to avoid highlight clipping. This method sure is risky if shooting ETTL. Surely a slightly noisy image would be preferred to one in which highlights are burnt out accidentally. I'd suppose that this method would be most suitable for those who shoot in predictable conditions, tripod mounted and who would rather not go into exposure blending/HDR/nd grads :) thanks
December 14, 2012 02:37 am
Nikon seems to over-expose every image for me on my d80 and then also on my d7000. This was maddening to me, but now I think they may have done it on purpose. I've been continually putting my exposure compensation to -.7 but now I think I will stop doing that to see if my final images work better. Thanks!
December 14, 2012 01:57 am
As long as the image doesn't clip on EITHER end I could see doing this for the highs OR the lows depending on which end of the spectrum requires more detail to be shown.
The Histogram is simply a visual to show the distribution of info. Read it then decide what to do with it.
Thanks, Elliot, can't wait to experiment.
December 14, 2012 01:50 am
Terrific article. I must admit, I was skeptical as I began to read it. But, the technical explanation and the example were totally convincing. I shoot a lot of landscape and will go out and try this asap. Thank you, Mr Hook!
December 14, 2012 12:53 am
Great article! Learned a lot from it. Exposing to the right is a great way to prevent clipping the blacks in an image.
December 13, 2012 11:32 pm
A very well-written article. Thanks! I've been exposing more to the right for some time now since Adobe came out with the latest version of Camera RAW (7.0) that does a marvelous job of recovering too-bright pixels with the "highlights" and "whites" sliders. I'm getting great results.
December 13, 2012 09:29 pm
Scott - I think you will find that practically “Pond—Moonlight” and “Moonrise, Hernandez, New Mexico,” were effectively "ETTR" Surely the whole purpose of his zone system was to determine the film processing technique in combination with the printing technique to maximise the data available in highlights and shadow areas of the picture. This was of course only possible with large format work where individual plates could be separately processed according to the data required and really has no relevance to roll film work.
December 13, 2012 08:23 pm
Good article. i have used this technique in the last months because noise to signal reduction in the dark areas is fantastic. I recommend to try it.
December 13, 2012 07:09 pm
I hear what people are saying about 'art' and that sometimes it can be under/over exposed - because it's art - and this is something I very much stick to in my work - but the argument is irrelevant to this article. It's true and worth saying always- but it's not a valid debunk. This was interesting and if I ever find myself shooting landscapes (which I so sometimes!) then I'll give this some thought and see if it adds to the 'art' of my shot. But if not, that's fine :)
December 13, 2012 04:31 pm
IMHO, "Exposing to the right" is much easier to do (and prevent highlight clipping) if you use the zone system, in manual mode, to meter. It seems complicated but with practice, becomes second nature.
December 13, 2012 02:25 pm
Ahh, thank you for jogging my memory about the amount of tonal range at each end of the histogram - it had slipped my mind. Generally speaking I will slightly under expose so that I don't blow out the sky ('slightly' under exposing being the main word here). I will now be more consciously nudging my exposure up a touch and see how the results are. Some say it's cheating, but if I really, really want that shot I will always bracket my exposure as an almost foolproof guarantee. As with all articles on DPS - 10/10.
December 13, 2012 02:05 pm
Great article - you definitely have to pick the circumstance to use it. Also, great insight to the operation of the sensor itself.
December 13, 2012 01:03 pm
Very interesting. I am primarily a portrait photographer (glamour, pinup, profressional portraits etc.) and shiit in-studio with cold lights. I've been happily allowing exposure to lean to the LEFT in the comfort that I wasn't risking blowing out any highlights. To be honest, I haven't noticed much noise so maybe it doesn't matter so much for what I'm shooting. I was told (long time ago) that once you over-exposed, you lost detail and could never recover it, but under-exposing gave you at least the chance to correct.
So my question is, is would I have much benefit in using this approach considering I'm shooting in a controlled environment, mostly concerned about skintones etc. and shooting raw? I do know that constantly checking histogram is not alwasy practical in a fast moving photo shoot.
December 13, 2012 12:54 pm
Great article. Thank you. I can see pleanty of debate possibilites but you can't deny the image quality in the cropped shots. Yes if the file size is larger it is due to more usable data it is a better method.
December 13, 2012 11:53 am
Thanks for the article! It was very helpful!
December 13, 2012 10:11 am
Scott - you're right, histograms are a way of showing how data is distributed, but understanding that distribution and what it means to your image quality is the message here, not that the histogram is the be all and end all. It's just another tool.
Blake - you're right, it could maybe have been titled 'The benefits of not exposing to the left", but that's just because of the example I chose. In this instance, a 1/3rd of a stop increase in exposure resulted in the sky near the horizon being blown, so the image is exposed as far to the right as I could, in camera, without sacrificing highlight detail. The 'ETTL image' is just underexposed really, but shows the benefit of exposing correctly/ETTR in terms of image noise/quality in the final, correctly exposed image.
December 13, 2012 09:55 am
Thank you for this explanation! I've been doing this for a long time without actually understanding the details behind it. Seems to me my camera regularly underexposes, often likely due to the metering point, and so I regularly bump up the exposure to compensate. I do so manually, not as exposure bias, such as with this photo (+2.5).
December 13, 2012 09:53 am
If you over expose you will almost always loose the sky.
If you work with the under-exposed image and use SELECTIVE histogram correction (you know, with the masks for example), you will still have some nice sky.
If you work with the over-exposed image, the sky is easily BURNT FOREVER.
Debate, it's interesting!
(crappy english from Italy, sorry about that)
December 13, 2012 09:08 am
The world of exposure IS different with digital sensors now. For landscape photography the ETTR is best way to optimize the DR of the camera while minimizing noise especially in high DR situations. This is the method I use everyday to set my exposure to shoot RAW with manual settings. It is not time consuming, is highly accurate and delivers great results every time.
The potential of overexposure exists with this method and requires that you know your camera well to avoid it in most cases.
December 13, 2012 08:30 am
Histograms are a method of showing how data is distributed. I don't frame histograms and display them in galleries nor publish them in my portfolio. There is no "correct" histogram for exposure data.
The "Pond—Moonlight" wasn't "exposed to the right," nor was "Moonrise, Hernandez, New Mexico," nor was ... (you get the idea)
December 13, 2012 07:20 am
Good article, and I like your point, but I don't think your example is truly illustrating it, or at worst it is misleading. The first paragraph sets up the debate as being between "correct exposure" vs "ETTR". But in your example it looks to be more like ETTL vs ETTR or really more like ETTL vs "correct exposure". Shouldn't you have used an image with a more evenly distributed histogram instead of under exposing?
Furthermore, your processed images look to be exposed even more (lighter) than the ETTR original. One would assume (based on the premise of your article) that the point is to over expose (without clipping) and bring the exposure back down to "correct exposure" in post processing.
Of course an image that is under exposed purposefully and then boosted way up is going to look worse than an image that is properly exposed and then slightly adjusted brighter.
I will have to conduct my own tests to see what my results are, but again I think the point is a valid one, just not the best example. Thanks!
December 13, 2012 07:14 am
I feel bad the most of my pics are not right exposed! Maybe Im so excited shooting subject?
Thanks for sharing this!
December 13, 2012 06:30 am
Interesting debate. I can see how it works to benefit the shot by your point of view. If you believe it to work for you then it works and those that don't shouldn't read past the first paragraph. I think it has it's place and I tend to lean toward the right with you. :)
Shoot raw. You can never go wrong.
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