23 September, 2014

Expose to the right

Noosa Heads, Queensland

People whose opinions I respect, seem to differ about, "exposing to the right."

Expose To The Right (ETTR) is a tactic designed to exploit the way that digital files are organised. The tactic is based on the recognition that half the digital data of any photo is in the brightest stop, half of the remaining data is in the next stop, and so on. This means that when you get down to the shadows, there’s not much information left to be manipulated — or printed.

The "right" in "expose to the right," refers to the right (brightest) side of a histogram. The theory is to expose the image so as to push it to the bright side without going to white ("blown" highlights). The seeming overexposure will then be pulled back down in the post processing of the RAW image. (This is not useful for JPEGs.)

There's no information (except pure white) in a blown highlight. So, unless you really have a bright highlight, like a spectral highlight from a metal object for instance, you probably don't want to go there. If a shiny nose or forehead gets blown out in a portrait, for example, then the portrait is probably done.

If histograms are a bit of a black art, then I suggest the Luminous Landscape discussion of histograms as a precursor to this discussion.

If you're interested in the debate, then here's where to look. (If you don't want the debate, then you can skip down to my view at the foot of the post.)
So where do I stand? I agree that ETTR can be a useful tactic. But care is required when you start pushing up the exposure. And, I agree with Ctein that times have changed; that cameras are now much better at delivering files with lower levels of noise, and noise reduction in post processing is much better at fixing it.

So, if:
  • You know how histograms work in general and how it works on your camera in particular; and
  • the exposure range of your scene falls comfortably within the exposure range of your sensor; and 
  • you're already at the base ISO; and 
  • there's detail in the shadows that you'll want to bring out; and 
  • the shot will be displayed in a medium where that shadow detail will actually show; and 
  • no part of the scene will get blown out unintentionally by moving to the right; and 
  • you have the time to consider all these matters while still getting the shot; then
Go ahead, expose to the right.

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