Before we get stuck into todays post, let me just clarify that the following words are designed to speak to the digital photographer not the analogue, and is only applicable to those of us that shoot in raw format.
So what is ETTR, or expose to the right?
ETTR is a fundamental rule if you are shooting in raw and plan to do any level of post processing. It’s basically as described, you expose for the highlights by keeping a close eye on your histogram.
What is raw?
Raw is a shooting format like a jpeg. A raw file is simply 100% of the image data that was captured by the sensor when we pressed the shutter vs jpeg which is around 40% of the image data. If you shoot raw you keep it all, if you shoot jpeg the camera automatically deletes 60% of the data.
What is a histogram?
A histogram is a visual guide to how tone is distributed throughout your image.
So based on what the histogram is telling us, we should be close in saying that this image has a good tonal distribution, with deep blacks, bright whites and a good range of mid-tones. It when the tones are bunched up at either end that we run into trouble as when we see this happen it means we have blown the detail on either the blacks or the whites, this we want to avoid unless it’s done on purpose.
So getting back to ETTR, and the raw image. Look back to the histogram on the right, where the black arrow is. Now run your eye til the end of the histogram where the white (highlights) tones are greatest, this is about 1.5-2 stops of light. It’s in these stops that over 50% of the raw image data lives, the other 50% is distributed from the black arrow to the left where the black (shadows) tones are greatest. So we must make sure that we have data in these stops, otherwise you will only get so far in post. We must always get as close as we can to the edge but without going so far that we blow the highlights. This is exposing to the right, and this will improve your photography and post production no end.