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Easy question about Photoshop (medium of all pixel signals)

post #1 of 9
Thread Starter 
I have a problem in Photoshop. I think it's easy, but I can't figure out how to do it.

I have this RGB image. Then, I need to create a grayscale copy of it. But I need to do this manually. Look:

- First, I need to create a grayscale copy of each R, G and B layer. So, I will have three layers, each of them grayscale corresponding to the signal intensity of each color.
- After separating each channel, I want to add all of them, to create the final grayscale image I want, but here is how I want it:

Each pixel in each channel will vary from 0 to 255. What i want is that in the red channel, the value will be multiplied by 0.3. On the green, by 0.59, and on the blue, by 0.11. (R x 0.3) + (G x 0.59) + (B x 0.11).

How can I do this?

Thanks a lot!

ps.: I know it's the channel mixer tool, but what values (and where to put) should I use to accomplish the desired effect?
post #2 of 9
Thread Starter 
OK. Nobody knows ?!?
post #3 of 9
You could try "action" called "custom rgb to grayscale". It's not actually what you are looking for, but has good control over different chanels in changing to b&w.

I understand what you mean, but I don't get it why to do it so complicated way? Is the workflow you desgribed a must, or can it be more simple if you could get similar results in an easier way?

Edit: The custom rgb to grayscale is in "production folder" in Action tab. (at least in CS2)
post #4 of 9
Sorry dont know photoshop well enough to be able to guess on that one. I would imagine it is fairly simple to do in Gimp with the scripting language, but I dont know if Gimp will work for you on this project(IE Is it destined for digital or print) or if you are even willing to look at learning the scripting, which I couldnt help you with myself, sorry.

Seablade
post #5 of 9
And yes the channel mixer is what I would be looking at to do it as well, creating duplicate layers with each and then flattening it, but I unfortunatly dont know the numbers you would want.

Seablade
post #6 of 9
Humm... Try creating 3 duplicate layers of the image. Go to the first duplicate and go to image/adjustments/levels and drag the channel box to the the respective color (red/gree/blue) and drag the right most slider just below the input levels all the way to the left. I think this will work with what you are trying to do. I know there is a better way to do this, but i dont remember exactly how to do it.
post #7 of 9
The problem is he has specific requirements for the summing output when he flattens these layers, that to do this correctly would need specific numbers for intensities of levels on those identical layers, those are what he is looking for I believe.

Seablade
post #8 of 9
Yup, channel mixer. What you are doing is for each pixel converting the color (R,G,B) into (0.3R+0.59G+0.11B, 0.3R+0.59G+0.11B, 0.3R+0.59G+0.11B), so the new R = 0.3R+0.59G+0.11B, new G = 0.3R+0.59G+0.11B, new B = 0.3R+0.59G+0.11B.

You can do this via the channel mixer by selecting Output Channel Red and setting the sliders to 30% for red, 59% for green, 11% for blue, then before pressing OK select Output Channel Green and repeat (30% red, 59% green, 11% blue), then go to Output Channel Blue and do the same thing, then press OK.
post #9 of 9
Thread Starter 
(later answer after a 2 week vacation)

Exactly jacobi, thanks... I was trying to create a B&W image by manually adjusting the luminance signals of each color.

In case any of you were wondering, this was what I was trying to reproduce. Photoshop's grayscale does not follow this rule (it does not follow the "33.3% each" either)...
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