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Channels for B&W conversion

PostPosted: Tue Apr 07, 2009 2:54 am
by MichelB
A very interesting resource on Retouchpro:
http://www.retouchpro.com/forums/photo- ... f-vid.html
Another thread on this topic:
http://www.retouchpro.com/forums/rp-tut ... r-ten.html

Remember that with smartcurves, you can even create layers from the L*a*b a and b channels in Elements... details later on.

Re: Channels for B&W conversion

PostPosted: Thu Apr 09, 2009 9:48 am
by squirrelflight
Thanks for the links! I'm going to try that action out tonight..

And I'll be anxiously awaiting more on the channel layers in smartcurves!

Re: Channels for B&W conversion

PostPosted: Thu Apr 09, 2009 10:40 am
by MichelB
squirrelflight wrote:
And I'll be anxiously awaiting more on the channel layers in smartcurves!


Here it is:
Test it with the following image:
http://www.prestophoto.com/photos/view_image ... itcomments

First duplicate your background
Then use smarcurves with the Lab mode
- to keep only color and eliminate tones, move the lightness end points to get an horizontal line in the middle of the graph= 50% luminosity
- to eliminate the blue/yellow component (b), move the a component horizontally in the same position.
Click ok

The result goes from green to magenta (a channel)

http://www.prestophoto.com/photos/image/1355747/34004
http://www.prestophoto.com/photos/image/1355748/34004
To extract the color, add a green (or magenta) solid color fill in difference mode. Merge down (Ctrl E) and desaturate (Shift Ctrl U)
To get the most of the mask, use levels or auto levels (Shift ctrl L)

To extract the a channel, do the same by neutralizing the b channel and using blue or yellow solid color fill.