You stretch the contrast of the mask to have mid-tones at like -6 or -8 EV, then you manipulate the the right-hand part of the chart, which now actually covers the upper range of brightness. The mask’s contrast can be very different from that of the image.
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Yes, I know all this, but I’m saying there’s no precise way of entering values to work on a specific range. It gets fiddly depending on the image to get the exposure comp and contrast comp exactly how you want it.
I don’t want to beat a dead horse, and we’re veering off-topic here. But thanks everyone for their input.
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I thought that’s what the egif is for? It finds the edges well in my use.
I find it does an excellent job on the whole image, and especially brighter images, yes. But what I have in my head, on my wishlist, is a something like a picker to sample the darkest tone and brightest tone, so it automagically spreads that range across the nodes of the Tone EQ.
For example, say you have a picture of a white-sand beach. Beaches tend to have little hollows and peaks on them, a bit like waves. With a photo taken in certain conditions, the EV values of the hollows and the peaks might be very close. So if I want to increase contrast on that beach, I might be looking at a very narrow EV range. By messing with the Exp comp and contrast comp sliders, you can sometimes get to where you want, but it’s not always easy. What I think would be cool is to grab a picker and sample the hollows, then sample the peaks, and you would just have this narrow EV range spread across your nodes. Then you can manipulate the contrast in this range.
Ultimately the Tone EQ might not be the best tool for this.
In Color Balance RGB, you could sample a tone between the darkest hollow and brightest peak as your fulcrum, then adjust the contrast slider. But this usually requires some parametric masking to ensure the brightest and darkest parts don’t clip.
I don’t know if I’m making myself clear, and I want to emphasize that this is not a big problem of mine. I usually find a way to do what I want. But I usually find that there’s quite a bit of fiddling with masks - whether that’s the EIGF in Tone EQ or parametric masks in other modules.
There are lots of tools, so we’re kind of spoiled for choice really. In fact, the old Shadows and Highlights tool is very easy to use, and by decreasing the highlights while increasing the white point, you can do exactly what I was saying about the beach. It’s just not the best module for scene-referred editing…
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I use color balance for this, particularly the offset luminance for the black point, and gain luminance for the white point. This gives you an arbitrary and easily controllable stretch of the histogram, without any masking and their associated artifacts.
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I am not sure that is very useful in practice. Practically, any image with darker areas will have some pixels close to the black level just because of noise, and conversely, specular highlights will give you some pixels which are clipped white. We can of course winsorize but even then some judgement may be required.
Noise effects can be largely eliminated by sampling an area, not just one pixel.
A more important problem in my view is that when you correct a sharply delimited tonal range, you have to be very careful at the edges of that range, to avoid inversions of the tone gradient over those edges. E.g.: darkening a selected gray area on a darker gray background: go too far, and your selected area becomes darker than the background… And “increasing contrast” means that you darken the dark tones, and brighten the bright tones.
So you either use a mask with feathered edges (making the tonal selection less “sharp”, but that only diminshes the problem) or you keep the tonalities at the edges fixed. But that means that contrast near those edges is changed in the opposite direction from your main contrast change (cf. filmic/sigmoid: more contrast in the mid tones means less contrast in shadows and highlights).
This issue is one of the reasons tone equaliser uses a such a blurry mask by default (another is that that helps keeping local contrast).
In the case of that beach, wouldn’t it be better to select the area of interest with a mask and add local contrast?
We are getting rather far away of the original topic, though
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