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Subject: Re: Exposure to the right and tone placement

-->Disregarding highlight recovery (which won't work if all channels are blown) I've lost 2048 levels.

Well, no, not really. You've lost everything that's too bright to capture,
but levels are an artifact of the digitization process, not something
that exists in the scene, which is for our purposes an analog stream of

I would consider photons and the electrons they produce in the sensor via the photoelectric effect to be more akin to digital than analog, since they are discrete and can be counted. I regard analog as continuously variable. That said, if overexposure causes the 12 bit AD converter to overflow, data are lost but some reconstruction is possible through the genius of Thomas Knoll.

If, on the other hand, you underexpose by a stop, you really have lost
2048 levels in the camera.

That loss may be tolerable since 200 levels at most can be seen by the eye in a print, and my highlights would still be preserved. Of course, a one stop underexposure is not good technique and I fully believe in exposing to the right within reasonable limits. Since I currently use an amateur camera with lossy compression of the raw file (Nikon D70), highlight recovery is less effective and I feel more comfortable leaving myself a little headroom. Your method is probably better for a professional with a professional camera.


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