At 11:00 PM 11/24/2008, Fernando wrote:
>...
>Also, I've just learned what could be old news for you the experts:
>sharpening using brightness channel in LAB mode.
This is one of my standard techniques as I like to use Lab mode.
Luminance sharpening can work better if there is noise in the image.
It helps avoid increasing chroma noise and chromatic aberration
along edges.
I suspect there is a way to do the equivalent in RGB, perhaps with
a luminance blend mode of a another layer? But that may not
work as well as Lab mode at preventing color side effects
along the edges.
For example, creating an edge mask from a channel that is created
from RGB luminance, then blend using luminance.
... all speculation on my part as I have never tried this.
As with anything Photoshop, there are many ways to do things.
Here is an interesting method:
http://photoshoptutorials.ws/photoshop-tutorials/photo-retouching/edge-sharpening.html
I suspect the halo effects from sharpening are similar to over-shoot
in filters. Only Bessel filters produce no over or under shoot in a step
response. Bessel filters have a very smooth frequency transition.
Very sharp filters will have over/under-shoot in the step response.
Wayne
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