Separating saturation from a contrast adjustment

[ajohnw]

Rawtherapee has what it calls standard and saturation with value blending. Also film like and another which will change highlight behaviour.

I think Ted needs to be careful here. Applying a curve change alters contrast in that region. The saturation and value blending hardly shifts anything at all. Standard changes all 3 significantly.

This is the result visually copying the curve from the post, same one applied to both.

Standard



Saturation and Value blending, if it was LAB I suspect they would call it that as they do everywhere else.



Then for comparison GIMP's Value curve. Couldn't use the same curve so bound to be some difference but I would say it's probably more aggressive than RT's. I didn't try to match the RT images, just the curve.



If switch GIMP to an Alpha curve this happens - have to add the Alpha channel manually these days.



I could load it up in some others and even add a LAB curve I expect but that one should try and mimic eye behaviour as colour lighting levels change - I think. Only played with briefly. I suspect that would have to alter all.

John
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[rpcrowe]

here is the image with the foliage selected and -30 desaturation applied

[xpatUSA]

Rawtherapee has what it calls standard and saturation with value blending. Also film like and another which will change highlight behaviour.

I think Ted needs to be careful here. Applying a curve change alters contrast in that region. The saturation and value blending hardly shifts anything at all. Standard changes all 3 significantly.
John
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There appears to be a misunderstanding here. All I wanted to do is replicate the OP experience but with a color card image so as to get some numbers. So, what exactly do I need to be careful of? Here's what I did:



To reduce confusion, I'm now going back to delete the Lab result form my earlier post. I wasn't trying to fix anything with it and certainly was not recommending it to others as a fix either.

[xpatUSA]

Hi Ted,

Interesting. Glad to see that I understood the L curve in LAB space correctly. No need to apologize for the statistics, at least to me.

One question. You wrote this:

Then I applied a luminosity tone curve which was the same shape as that posted in the OP.

I don't know Raw therapee, so I don't know what you mean by a 'luminosity tone curve.' In photoshop, if you apply a tone curve without doing anything else, it applies the change to the color channels. You only get a luminosity-only curve by setting the blend mode to luminosity, rather than RGB, or by switching to LAB as you did. I'm assuming that the luminosity curve you are referring to is the garden-variety adjustment that acts on the color channels. Is that right?

Dan

I believe so, Dan. In my turn, I have no idea what is meant by "setting the blend mode", sorry. Having said that, please see the screenshot of my adjustment in my previous post #23.

[Richard Lundberg]

They all look the same except the last two, which are washed out.

[ajohnw]

They all look the same except the last two, which are washed out.

That's the general idea Richard - damp down mist without changing saturation values. Where they aren't as flat something else has been done to them as well.

I have removed mist from a couple of shots posted on here using a contrast mask following by a graded contrast increase. More increase added to mid contrast levels. I would need a much bigger image to start with to do the same with this one.


One of Christina's as some one criticised alignment.




Much less aggressive this time




Manfred was up to "999" layers on this one from raw. This is the sort of thing that crops up from raw




Colin's PP was better in "!! some ways !!" than mine but even he had to add an Orton effect. I didn't and could probably do better now




To me this all means I will be sticking with the initial use of a contrast mask.

John
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[DanK]

I believe so, Dan. In my turn, I have no idea what is meant by "setting the blend mode", sorry. Having said that, please see the screenshot of my adjustment in my previous post #23.

I am guessing that the "standard" in the dropdown box over the curves tool is equivalent to "normal" in PS. From what you posted, it behaves the same way: the curve tool seems to act on the RGB channels