Quote:
Originally Posted by glend
… I usually limit luminance opacity to 17-20% depending on the object.
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Glen:
At face value, that would mean that you have just thrown out 80 to 83% of your luminance data. You may as well have not taken it if you are photographing LRGB.
If you are photographing RGB and producing a fake luminance layer from the colour data (with a view to reducing colour noise, which is the only conceivable reason) your maths will have negligible effect. It is easy to prove this: the values of neighbouring pixels have no effect on any given pixel.
The way to reduce colour noise without losing saturation would be to separate into L and RGB, filtering the RGB to reduce colour noise without affecting topographic data or losing saturation, and finally recombining the L with the RGB.
There are tedious methods converting RGB into HSV for example, and then topographically filtering the H without filtering the S or V, and converting back to RGB, which achieve much the same result, but if you've already separated into L and RGB, there is little point.
In summary, the way to increase the saturation is to increase the saturation, not to reduce the opacity of the luminance layer.
Mike
Postscript: I wonder if Glen is adding the luminance layer with properties set to "Normal" instead of "Luminance". That would explain the confusion.
