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Separate Luminance
July 2, 2009 - 16:43 — Roy Johnson
FX-Foundry/Color/Separate Luminance...
Creates two new layers: one containing the Luminance, and the other the Chroma information in the form of a Grain Merge. Optionally, it will color-enhance (maximize saturation in) the Chroma layer while still keeping it luminance-neutral.
This allows you to do noise-reduction and sharpening on the two layers separately.
Update (23-Jul-2009):
Noticed that highly-saturated colors exceed the ability of the grain-extract/grain-merge to handle without clipping the color, so I have made the excess color get folded into the luminance layer. Most of the time, it will be un-noticeable, and even when it is, it shouldn't make any real difference. If you want to be sure your Lum layer is pure luminosity, you can check Excess color on separate layer. When merging, always merge onto the Lum layer rather than merging the two color layers together.
| Attachment | Size |
|---|---|
| roys-lum-separate.scm | 3.1 KB |
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Comments
Nice script for photographers!
Very useful, thanks!!
Pascal
Example?
Would sure like to see an example and a few instructions.
Thanks
Nick
How to use this script
The Unsharp Mask docs say
To prevent color distortion while sharpening, Decompose your image to HSV and work only on Value. Then Compose the image to HSV.
This script provides an alternative: Instead of the decompose-recompose cycle, you simply split the image into two layers. One has the gray values (Luminance) and the other has the Color information. You can do your sharpening on the Luminance layer and not affect the colors at all. As a bonus, you can see the effects in real-time, because you don't have to put anything back together to see the image.
In addition, it's often a good idea to do noise-reduction on Luminance and Color separately. You can apply a lot heavier noise reduction to the Color layer and your image won't suffer.
I don't have a good idea of how to show an example of this, because it's really preparation for editing, rather than a complete edit in itself. If you don't do Color Spiff, what you see after running this script is exactly what you had before running it; the information is just separated into two new layers. Color Spiff is just a boost to saturation, and there's nothing novel about that. I'll note that if the Spiff makes things too saturated, you can tone it down by adjusting the Opacity of the color layer.