Why Exposing to the Right (ETTR) is BAD!

Started Mar 30, 2013 | Discussions thread
(unknown member) Senior Member • Posts: 1,321
Not Exposing to the Right (ETTR) is BAD

ETTR is not bad. It is smart.  It is smart to record a photograph with the highest possible signal-to-noise ratio and this is exactly what ETTR does.

The physics of digital imaging tell us increasing exposure increases the signal-to-noise ratio of the shadow regions. The shadow regions are where the SNR of any exposure is lowest.  This means ETTR is critical to achieving the best possible result for the regions with they least amount of light.

Not every single highlight is always important to the aesthetic purpose of a photograph. By over exposing unimportant highlights, the SNR of the shadow regions is the best it can be. When every single highlight region must be retained to achieve the photographer's aethetic goals, then the SNR ratio of the shadow  regions will suffer. But in this case the exposure should still be as high as possible  without clipping the signal in all three channels.  You should still ETTR, but you must do so with  great care. This is difficult because practically all in-camera histograms are only estimate the real, but unknown, exposure since the histograms are computed from from JPEGs.  Fortunately flexible exposure bracketing is trivial  to implement on most modern cameras.

More signal is good.  Less signal is bad.  ETTR is good because it insures your photograph has the highest SNR possible.

By the way, exposure (SNR) also has a significant impact on dynamic range. Guess what? More SNR = more dynamic range.

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