channels/channel mixer question

DF
Posted By
David_Freed
Dec 7, 2007
Views
264
Replies
1
Status
Closed
Assuming I’m starting with a CMYK file, in the Channels window, I can select any one or a combination of the channels for an image. And if I do select more than one channel (say cyan and magenta), I’d be getting 100% of each.

I’m wondering how this relates to the Channel Mixer (CM). If I go into CM layer, select Monochrome, then if the source channels are at Cyan 100% and MYK are at 0%, would this be the same as viewing the Cyan channel in the Channels window?

And in CM layer with monochrome selected, if I had Cyan 66% and Black 37%, would this be like combining 66% of the Cyan channel with 37% of the Black channel?

And finally, in the Channel Mixer layer, the sliders go up to 200%, but I don’t understand how you get 200% of a grayscale tone when its already at or near black (100%) or white (0%). If I was viewing say 100% of the magenta source channel in CM, and some of the pixels were already showing 100% K, I don’t see how going up to 200% changes them, though it certainly would change some of the "lesser" pixels (for example at 55%, 67%, 12%, etc.)

Thanks, David

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GA
George_Austin
Dec 8, 2007
David,

You are correct on all points.

When the product of the slider percentage and the existing value exceeds 100% (as 200% slider * 75% existing value = 150%) 100% applies. Likewise, negative percentages become zero. The slider percentage applies globally so, as you point out, lower existing values will be affected even when higher values are blown out.

Checking the monochrome mode behavior in PSCS3, I am surprised to see that the default slider positions in RGB become 40/40/20, whereas they used to preserve luminosity (equivalent to 30/59/11), and in CMYK the default sliders are 100/0/0/0.

George

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