Question for Photoshop/LAB gurus about blend modes

Discussion in 'Retouching and Post Processing' started by JeffKohn, Nov 19, 2005.

  1. JeffKohn


    Apr 21, 2005
    Houston, TX
    OK, normally I use an action for sharpening that creates a duplicate layer of the image and lets me run my sharpening tool on that. This has two advantages, in that I can use "Luminosity" blend mode to help prevent color sharpening artifacts, and it also allows me to selectively apply the sharpening to only part of the image via layer mask (no sense in sharpening bokeh only to make it grainy, for instance).

    This works well, but reading the LAB book convinced me there are still some cases where sharpening the 'L' channel is superior to sharpening on an RGB luminosity layer. So for images where I'm already in LAB mode I'd like to do my sharpening there. Unfortunately there's no easy way to use a mask for selective sharpening when you're sharpening a channel as opposed to a layer (yes, there are a couple ways I can think of but they're rather cumbersome).

    So what I'm wondering is this. If I create a duplicate layer in LAB mode and change the blending to Luminosity, will I get the same effect as working directly on the 'L' channel? I would think the answer is 'yes', but if anybody can give me a definitive answer I'd appreciate it.

  2. JeffKohn


    Apr 21, 2005
    Houston, TX
    Hmm, well I'm still curious about the answer but it turns out not to be terribly relevent to the problem at hand because my sharpening plugin won't run in LAB mode unless only a single channel is active. Oh well. I think I'm going to stick to the RGB Luminosity layer for most of my sharpening unless I think the artifacts coudl be an issue. Being able to quickly paint out the background on the mask to avoid sharpening it is just too darned convenient. A similar effect can be achieved with the history brush, but it's less precise since you don't have the visual feedback from the mask showing you where you have/haven't applied the sharpening.
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