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Lightness channel sharpening and printing in Lab mode

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  #1  
Old 09-29-2005, 03:35 AM
cocasana cocasana is offline
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Lightness channel sharpening and printing in Lab mode

Hi there,
I was wondering if the color definition I loose converting from Pro Photo Rgb to Lab mode to apply Lightness channel sharpening is worth while on your opinion. At that point isn't it useless to convert back to ProPhoto Rgb? Why not printing directly in Lab mode?
Thank you very much,
Carlo
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Old 09-29-2005, 09:10 AM
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Duv Duv is offline
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Quote:
Originally Posted by cocasana
Hi there,
I was wondering if the color definition I loose converting from Pro Photo Rgb to Lab mode to apply Lightness channel sharpening is worth while on your opinion. At that point isn't it useless to convert back to ProPhoto Rgb? Why not printing directly in Lab mode?
Thank you very much,
Carlo
Hi Carlo.

Welcome aboard!!
I don't believe you loose color definition converting any profile to LAB. LAB sharpening is one of my most frequently used methods. I don't believe you can print in LAB mode so you have to convert back to RGB or CMYK for prepress.

Cheers

Dave
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Old 09-29-2005, 12:44 PM
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goose443 goose443 is offline
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If there's any loss it'll be from LAB to RGB though that should be small. The reason is that RGB's color gamut is smaller than LAB which really has none. The big loss will be converting to CMYK which, depending on the profile used will have a very restricted gamut. Still, if the photo warrants it, it is well worth the effort of correcting in LAB, especially L channel since you avoid color shifts.
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Old 09-30-2005, 12:05 AM
chromaticstyle chromaticstyle is offline
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better technique

you can lose color information converting from RGB to LAB and back, but it probably won't be much. but, there is a better technique for sharpening just the luminance of a photo, that will cost no loss at all!

once your ready to sharpen, make sure everything is flattened. run unsharp mask just like normal. with the following technique, i will actually oversharpen a bit more than normal. like .2-.3 more on the radius, and 50%-100% more on the amount.

after your run unsharp mask, go to edit > fade (unsharp mask).

change the blend mode to 'Luminosity' and fade it back a little bit, usually to 70%-80%.

spladink! just like that. same as sharpening in LAB. hope this helps. good luck!
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Old 09-30-2005, 01:14 AM
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Duv Duv is offline
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LAB vs RGB Luminosity. Something to consider. (Compliments of Dan Margulis: Photoshop LAB Color) To me the color looks better in LAB plus you don't see the white fringing. While I do most of my sharpening in LAB, most oftern I don't see a difference but when I do it almost always favors LAB.

Cheers

Dave
Attached Images
File Type: jpg D-Origyellow_sign_to_sharpen.jpg (87.5 KB, 12 views)
File Type: jpg D-LAByellow_sign_to_sharpen copy.jpg (91.5 KB, 13 views)
File Type: jpg D-RGB-Lumyellow_sign_to_sharpen.jpg (94.1 KB, 13 views)
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  #6  
Old 09-30-2005, 09:21 AM
cocasana cocasana is offline
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Thanks to you all

for your very interesting and usefull replys!
Carlo
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