+1 for you to share the raw file. I'm curious now On Sat, 4 Feb 2017, 13:38 Stéphane Gourichon, < [email protected]> wrote:
> Le 04/02/2017 à 04:03, Anton Aylward a écrit : > > I have a picture of a white barrel cactus (Cleistocactus icosagonus) which was > taken in strong light, bringing out the white 'leafs'. The illumination is > along one edge, rather like a crescent moon. The crescent is overblown > whenever > I convert to JPEG, and I can't figure out how to manipulate it down without > the > rest of the image being darkened or distorted. > > Other than ending up dealing with layers in GIMP, or somehow masking the > crescent, which, because of the spiky leaves might be awkward, what can I do > about this? I there some way to 'flatten' the top end of the white alone? > > I know some controls have sliders, but, for example, keeping the R&G&B all > aligned is difficult. Is there a way to do numeric input or lock sliders > together? > > Or am I just approaching this the wrong way? > > > > Hello. > > This is a case of overexposure in strong light, which is a specific case > of high dynamic range situation. > > Can you share the RAW file ? I'm curious about the situation and would > like to experiment. > It would allow to confirm that something can be recovered indeed. Else the > following will not be of any help. > > > No one has mentioned global tonemapping, which is a tool intended for > dynamic range issues. > > It may be good here in spite of caveats : > > * You seem to want the rest of the image unaffected (which is virtually > never actually *strictly* desired, for it would look unnatural anyway). > * Drago operator feels like a hack when you read the research paper > https://scholar.google.fr/scholar?cluster=11303574887036255127&hl=fr&as_sdt=0,5&as_vis=1 > * Drago operator takes some practice to get something good, and has some > surprising properties. For example, changing the (upstream of the filter) > exposure settings actually changes resulting color rendering. It's easy to > wreck the picture by fiddling blindly with the settings. > > That said, it might be useful in this case. > > * (suggestion) Take snapshot (left column) to allow left/right > before/after comparison at any time. > * In most cases it makes sense to disable base curve when using global > tonemapping (because it is somehow similar to a basecurve in itself). > * Enable global tonemapping which defaults to drago. > * Because supposedly the picture is not that high dynamic range and you > don't have much dark details to recover, in tonemap module possibly adjust > bias, towards 1 for a weaker effect/more natural rendering. > * Then focus on color: to get the "warmness/sunbathing feel" right / > natural, adjust upstream exposure. Easiest is to use mouse wheel on top > right histogram (on center or right of it, not left part of histogram which > changes black level). > * If resulting picture is too dark or bright, in tonemap module adjust > "target" parameter in small steps. > > > Hope this helps. > > > -- > Stéphane Gourichon > > > ____________________________________________________________________________ > darktable user mailing list to unsubscribe send a mail to > [email protected] > -- Regards Dave Jones 0794947061 ____________________________________________________________________________ darktable user mailing list to unsubscribe send a mail to [email protected]
