How do PS CS mix channels ‘Image->mode->Grayscale’

CT
Posted By
Constantin_T
Oct 6, 2006
Views
375
Replies
2
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Closed
I’ve always thought that converting RGB image to Grayscale with menu command:Image->mode->Grayscale works exactly like channel mixing with some internal presets like (?R=30%G=60%B=10%) sum 100% and I could do exactly the same with channel mixer if I could fit the numbers. But I couldn’t. Than I measured gray colors had converted of pure R=255, G=255 and B=255. It was 160% in sum! I’ve tried it few times with different profiles – approximate the same result. Why this happenes or am I doing/understanding something wrong?
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Ann_Shelbourne
Oct 6, 2006
You use the Channel Mixer to adjust the way that you want your GS to be adapted from your color image.

In Channel Mixer, check the Monochrome box.
Then enter red=30%; green=60%; blue=10%.

You can use any other values but the total of all three values should = 100% to maintain the density range of the original.

Changing the percentage that you take from each channel is similar to using color correction filters with black and white film.

Increase the red and green values and cut the blue ones to darken a blue sky in the same way that a Wratten yellow filter would do; or increase the green and cut the others to lighten the GS rendering of green grass like a Wratten Green filter would do.
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Chris_Cox
Oct 6, 2006
It’s not that simple because you aren’t taking the exact values from your RGB colorspace and the transfer curves from that or the grayscale space into account.

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