Lab luminosity is not necessarily the same as calculating the luminosity from an RGB channel and this would be influenced by Gamma, color profiles and other things. You would need to actually produce the luminosity result using channel operations e.g. with Calculations or stacking duplicate layers.
Lab luminosity is not necessarily the same as calculating the luminosity from an RGB channel and this would be influenced by Gamma, color profiles and other things.
I tried it with the lightness channel from the HSL (derivative of RGB) color space, but I got the same result.
You would need to actually produce the luminosity result using channel operations e.g. with Calculations or stacking duplicate layers.
I don't have any idea how I can produce luminosity from a RGB image with the channel calculations. A web link would be greatly appreciated ... thanks.
When a channel with its inverted are added together, their opacities are perfectly added to each other ... all the pixels are turning to pure white (255,255,255).
But, when a channel with its inverted are used as masks in the layer panel, their opacities are not added to each other perfectly for showing the following layer ... in my case HSL adjustment layers.
Is there a solution for this case?
Turgay, if your intention is nothing else but image desaturation, you may use
Image Adjustment > Desaturate
Image > Mode > Grayscale
Image > Mode > RGB Color
In Lab an image can be desaturated by setting a=0 and b=0 simultaneously.
This is as well a nice approach for assigning a tint (a not 0, b not 0).
HSL or HLS is not a colorimetrically correct color system.
Best regards --Gernot Hoffmann
Thanks Gernot ...
HSL adjustment layer was just an example ... indeed, I want to correctly split highlights and shadows with a luminosity mask (without any leakage between the masks) for controlling different type of adjustments for different tonal regions.
I would like to ask a question about the Lab color model to you ...
Can we separate saturation from the a and b channels for a saturation mask?
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I would avoid HLS (HSL). This is more a kind of navigational system, an easily
understandable color space but much less one for calculations (therefore I had
used a somewhat modified approach in my doc).
Lab is a good choice. Saturation is approximately the radius in the plane a-b,
(vector length from the origin to a point (a,b) ).
For your purposes I would recommend this proceeding:
Image > Mode > Lab Color
Layer > New Adjustment Layer > Curves
...modify L and eventually a,b
Layer Style > Blending Options
Here we have for each channel two sliders for top layer / bottom layer.
Each slider can be split by ALT+LeftMouseClick (move mouse) in order
to create soft transitions.
This is a direct approach for selective corrections. With masks I'm not
Hope this helps a little.
Best regards -- Gernot Hoffmann
Thank you so much ...
Very nice approach for tone and color corrections.
I think ... I should spend much more time on this.
Thanks again ...