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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 photons. You haven't "lost" anything, you've simply blown the highlights by making an incorrect exposure, which, as I've said repeatedly in this thread, is not something anyone here is advocating. You've still captured 4096 levels, they just aren't the ones you wanted because you screwed up the exposure. If, on the other hand, you underexpose by a stop, you really have lost 2048 levels in the camera.

-->Of course, with a short scale subject whose dynamic range is less than that of the camera we do have exposure lattitude, but I agree it is best to place the highlight as you suggest to cut down shadow noise.

That's really all I've been saying, throughout this thread. You always want to make full use of the camera's dynamic range. When the scene dynamic range fits inside the camera's, that means you want to expose as hot as possible. When it's overrange, the critical decision is where you place the highlight point: You may want to blow highlights to capture shadows, or you may want to clip shadows to hold highlights, but the last thing you want to do is to underexpose, because then you are NOT making full use of the camera's dynamic range.

In practice, the Canon cameras I shoot will almost always allow a stop of highlight recovery—things start getting nasty when I need to recover more than a stop and a half. Some cameras offer less headroom, others offer more. A good deal also depends on the absolute luminance of the blown highlights—if the sun is in the frame, for example, you may only have blown 1 stop of your intended capture, but there are about 18 stops above that that are driving the camera into its nonlinear range, so significant highlight recovery tends to produce strange color artifacts.


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