The Expose-to-the-Right (ETTR) Debate

Man versus Nature. Boulder County, Colorado, 2012

“Debate?” you ask. “I didn’t know there was a debate!” I thought the same until I started investigating a bit. ETTR is not necessarily what you ought to be doing. At a minimum, you need to understand what it is all about, then you can make your own decision.

Before you read farther, make sure you understand that this technique does not apply to you if all you shoot are JPEGs. It does apply when you shoot RAW and you open your images in a RAW converter where you then make your initial basic exposure adjustments. The links I give below will explain all of this.

Now, lets start with some background–what is ETTR? The idea stems from the fact that digital sensors capture many more levels of data on the right side of the histogram (that is, in the brights) as opposed to what is captured in the dark shadows. (Dark Shadows…now that was a good TV program! Barnabas! But I digress.) So, the idea goes, I should always make sure the pixel graph of my capture sits as far to the right in the histogram as possible without, of course, pushing it into the right hand wall which would mean desired highlight detail might be clipped. Then, in post-processing, I use the Exposure slider (or other, more subtle, techniques) to set the desired final exposure. Doing this, so the theory goes, will make sure I avoid unnecessary noise and/or banding in the shadows as I try to pull detail from those darker areas.

For a very detailed explanation of the theory of ETTR as well as the various arguments related to employing the technique, go to the extensive and interesting Luminous Landscape article by Michael Reichmann, entitled “Optimizing Exposure“.

There are, however, some important problems with ETTR which may negate its practical effectiveness even if the theory is sound. I’ll list three:

1) The histogram, being based on the in-camera JPEG conversion of your RAW image, is not an accurate estimate of where the histogram actually lies. You could be clipping highlights without knowing it. So, in an effort to avoid shadow noise and banding you could end up with crappy highlights.

2) What’s more…the histogram does not display all pixels–only a representative sample. So, if you ETTR and push your graph right to the toe of the right hand wall, you may in fact have blown highlights and not know it. Once your highlights are clipped, they can’t be recovered.

3) Today’s digital cameras are much better in terms of capturing dynamic range and we don’t have quite the same issues with shadow noise and banding as we had back in 2003.

You can find a really good summary of the problems with ETTR at The Online Photographer website at this link. Ctein’s article is appropriately titled, “‘Expose-to-the-right’ is a Bunch of Bull”. He makes some very good points.

Naturally, I have to conclude with my personal opinion. ETTR may, in fact, work in some situations–especially in cases where you are particularly worried about getting as much detail as you can out of the shadow areas of your image. But, beware that, in the process, you might very well clip important highlights and thus ruin you image in another, unexpected way. So, think about what your intent is, analyze the dynamic range of the image you are trying to capture, then make your decision whether ETTR will work for you in that particular circumstance. That is my plan, anyway. Good luck to you!