On 1/11/13 12:55 PM, Robert William Hutton wrote:
> Sounds to me like what you really want to do is raise the gamma
> rather than raise the exposure.

Gamma is a non-linear modification that has no equivalent in real world
photography.

Exposure is a well understood concept (multiplication with a fixed
number) that maps directly to the real world.
Then you want to manipulate the full tonal range of the resulting image,
possibly bringing parts that were pushed >1.0 back into to 0..1 range to
recover detail.

Of course, you can partly express this with a gamma curve, that is:
anything that was shifted outside 0..1 and the brought back into that
range. But if you want to keep 5% of your pixels still overexposed gamma
won't let you do this. Lastly, it is anything but intuitive, in the OP's
use case.

Furthermore, when you want to work on parts of the tonal range and leave
the rest absolutely fixed, you need a lot of points on the tone curve
and it becomes fiddly and unintuitive.

I think the (between the lines) feature request of the OP is to extend
the working tonal range of the highlights/shadows module, by a certain %
or automagically, to the highest value present in the image.

So for highlight recovery, there would be modes of working:

- Normal (current code, clips at 1.0, no way to recover values pushed
outside that range by previous modules in the pipe or present in the
original image)
- Auto (highlight tonal region extends beyond 1.0, to highest value in
image)
- Extended (user defined % of values above 1.0 becomes part of
highlights tonal range, i.e. 80% means highlights can go up to 1.8, etc.
Maybe this needs to be a an exponential slider, instead of % though)

Does that make sense.

.mm


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