L*a*b* Adjustments - histograms

(Wayne Sutton) #1

When I activate the curves for the Lab channels in the Lab Adjustment module, the histogram for the L* channel shows up OK but doesn’t for the a* or b* channels. There is no histogram either for the CL and the LC curves, but there is one for the CC curve. I’m not sure whether this is normal or if there is a problem. I use the daily v5.5 builds.
Any help would be appreciated.

Wayne Sutton

(Morgan Hardwood) #2


It’s normal.

(Wayne Sutton) #3

OK thanks. The Rawpedia entries for the CL and LC curves show histograms in the example images in fact so I thought I had missed something.
The reason I asked about the a* and b* channel histograms was that I was experimenting with the following technique: https://petapixel.com/2017/09/14/using-lab-color-photoshop-add-color-punch-images/
However thinking about it, this may be simply what the chromaticity slider does anyway?

(Morgan Hardwood) #4

Then you may be right, this could be a bug. I will take a closer look later.

(Morgan Hardwood) #5

By the way, check out the Color Toning tool’s Regions method, it allows you to create masks.

(Wayne Sutton) #6

Will do, thanks for the suggestion!


Is there any update? Is it a bug, or did I do something wrong?

All Lab histograms are missing. And in ‘Linear’ mode the chart doesn’t show up at all.

RT v.5.5 on Windows 10

(Morgan Hardwood) #8

(Ingo Weyrich) #9

L* and CC have a background histogram, a* and b*(the one you selected in your screenshot) never had a background histogram.


And please add a color picker too. I use that combination a lot in Darktable.

(Ingo Weyrich) #11

Why not use the already existing?


Without the Lab curve there is no color location on the curve. They can copy that from Darktable.

(Ingo Weyrich) #13

Maybe I misunderstand you. Each curve in ‘Exposure’, ‘Lab* adjustments’ and ‘RGB curves’ has a picker

(Wayne Sutton) #14

as mentioned above, the CL and LC curve histograms are shown in Rawpedia. Does that mean they used to be there and were removed for some reason?

(Ingo Weyrich) #15

I don’t know. Maybe @Morgan_Hardwood knows