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Subject: Re: Exposure to the right and tone placement



OK. Back to the beginning.

Yes, the camera devotes half of its bits to the brightest f-stop. This is not in any way a good thing, it's just how things are.

To get the best image, you need to make use of all the bits. You've paid dearly for a camera that captures 12 bits rather than 8. If you want to avoid noise and posterization in the shadows, you want to capture all 12 bits. For a low-key subject, you have two choices:

1.) Make a capture that places Zone V at around 50% lightness in the camera's encoding of the tone scale—that's around level 47 on a 0-255 scale.

2.) Make a capture that is as hot as possible without clipping highlights, then use tone-mapping to darken the image.

In my experience, 2 works MUCH better than 1. It MAY involve negative exposure compensation in the raw converter, but the midtone control is Brightness, not Exposure, and it's the control that is most effective for placing the midtone when you tone-map from linear to gamma-encoded space. The tone mapping is not a simple gamma correction—it's whatever you make it, and the more bits you've captured, the more control you have over the tone mapping. It's not about preserving some mythic non-reproducible invisible highlight detail—it's about making full use of the camera's dynamic range to provide maximum flexibility on tone-mapping.

Where we came in was how to determine when we're running into irrecoverable highlight clipping. Trying to estimate where 255 lands by metering on 47 is a very uncertain excercise....

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