Expose to the right - ETTR

If you are into serious digital photography, chances are you are shooting raw files. There are several varieties of raw files, with several camera manufacturers using proprietary file formats. Nikon, for example, names its RAW files NEF files, while Canon uses the appendix CRW or CR2. One thing all RAW files have in common: they contain all the data recorded by the image sensor at the time of exposure.

Photographers then move to their computers to transform the RAW files into JPEGs or some other shareable format for practical use. This practice has spawned terms such as “digital darkroom” or “development”.

ETTR, or expose to the right, is a fully digital concept. Image sensors have a great deal of dynamic range and are capable of recording both shadows and highlights, but they do reach a point where shadows are dark and without detail. By the same token, highlights can also become washed out, totally transparent and without texture.

It’s all in the histogram

A good photograph makes optimal use of all the useful tones found between clipped highlights and image-less blacks. Photographers learn to expose so that their images fall right in the middle of this range.

Digital cameras can display a histogram for each individual image. The histogram is a graphic showing the distribution of dark and light pixels. The dark pixels appear at the left, and the light ones at the right. An average photo will usually show a histogram with most of the pixels in the center of the graphic, a curve with a bump in the middle of the scale. A full-frame photo of a white surface will produce a sharp peak of medium pixels right in the center. Of course, when you do this, your exposure meter is trying to produce a uniform grey image: that’s what it’s supposed to do!

Kill that noise

In order to avoid digital noise in the shadows (those pixels that collect on the left side of the histogram) some photographers choose to “expose to the right”, in other words, overexpose. This moves the histogram values to the right. When the RAW file is converted into an image, the photographer makes a negative exposure correction which moves the curve left, and returns detail and texture to the highlights… and produces shadows with very low noise!

Of course, ETTR comes at a price. First, there is an increased risk of clipping the highlights, with the resulting loss of detail, and an unusable shot. Also, the ETTR shot will look quite overexposed on your camera LCD, and will require heavier adjustments than you may be used to.

Your own tests and experience will help you decide if ETTR is for you or not. But many photographers swear by this practice. A simple internet search will provide you with more than you need to know, and hopefully supply some insight into which way you want to go. Wherever you end up, you’ll know a lot more about exposure when you’re done.