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DPChallenge Forums >> Tips, Tricks, and Q&A >> How do you separate CMYK layers in Photoshop?
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 05/15/2009 09:04:05 PM · #1
I am doing a silk screening project and in order to do a full color silk screen, which is apparently very difficult, i have to separate my selected photo into CMYK, one for each channel i assume. I tried duplicating each layer and changing the blending option to Multiply, and then i filled it with white. But I don't know what to do from here. In addition i have to apply the threshold adjustment so that there are no grays.
 05/15/2009 09:07:03 PM · #2
on the top bar third option is image, then mode and cmyk is the 6th one down, select it and in channels the seperations are there for you.

Message edited by author 2009-05-15 21:09:55.
 05/15/2009 09:08:46 PM · #3
I am on CMYK mode, but for silk-screening apparently i have to print off each colour? I'm not entirely sure. Anyone an expert on this?
 05/15/2009 09:11:26 PM · #4
They need the channels , the images look B&W but all you need is the luminosity for each channel

Message edited by author 2009-05-15 21:11:46.
 05/15/2009 09:12:09 PM · #5
Originally posted by BrennanOB:
on the top bar third option is image, then mode and cmyk is the 6th one down, select it and in channels the seperations are there for you.


I understand, but for silk screening i need to print off each channel. I kinda need a silk-screening expert here. I think i have to turn off each channel and leave only one on.
 05/15/2009 09:13:21 PM · #6
Originally posted by BrennanOB:
They need the channels , the images look B&W but all you need is the luminosity for each channel


so when i print off each channel, they should just be in BW with different luminosities?
 05/15/2009 09:15:16 PM · #7
yup, but usually they take a disk, if you print it they will have to scan them, adding another level of noise.
 05/15/2009 11:56:49 PM · #8
Originally posted by cujee:
Originally posted by BrennanOB:
They need the channels , the images look B&W but all you need is the luminosity for each channel


so when i print off each channel, they should just be in BW with different luminosities?

Yes, CMYK separations look like four different grayscale images of the sam escene. When you print from Photoshop, there should be an option to print separations. But unless you are printing to film for the silkscreeners, you should just be giving them a CMYK TIFF image file, which they can print or place as necessary. You can see what the four images look like by looking at the color channels individually (turn of the preference to display color channels in color).

Message edited by author 2009-05-15 23:57:28.
 05/16/2009 12:17:54 AM · #9
Originally posted by GeneralE:
unless you are printing to film for the silkscreeners, you should just be giving them a CMYK TIFF image file, which they can print or place as necessary.

If you give a CMYK (TIFF, EPS, PDF or PSD) file to a silkscreen printer, they'll know how to separate it. If YOU are the one printing the separations, then you need specific instructions from the printer on the line screen and correct angles for each channel. If you just copied the channel to a grayscale file and printed each that way, it won't work because the ink dots will all be stacked on top of each other.
 05/16/2009 12:26:11 PM · #10
Originally posted by scalvert:
Originally posted by GeneralE:
unless you are printing to film for the silkscreeners, you should just be giving them a CMYK TIFF image file, which they can print or place as necessary.

If you give a CMYK (TIFF, EPS, PDF or PSD) file to a silkscreen printer, they'll know how to separate it. If YOU are the one printing the separations, then you need specific instructions from the printer on the line screen and correct angles for each channel. If you just copied the channel to a grayscale file and printed each that way, it won't work because the ink dots will all be stacked on top of each other.


I am taking my file and printing it off at a store most likely, but I'm not entirely sure they will know how to print it off with the proper instructions.

I am the one who is doing everything including registering the 4 images and exposing it to the silkscreen. The only thing I need to be able to do is print off the 4 separations, but are you telling me that if i print off the images individually for each channel it won't work cause they will stake?

Message edited by author 2009-05-16 12:29:29.
 05/16/2009 03:45:51 PM · #11
The silkscreen process, similar to offset printing, requires the conversion of pixel densities in solid "half-tone" dots, which cover anywhere from 0-100% of the paper, giving the human eye the illusion of continuous tone. These dots must be be of a certain size, frequency, and angle, depending on the printing method. If you use more than one color, the screens must be placed with the dots at precise angles to each other to avoid interference patterns called moire.

Further, exposing silkscreens involves powerful lights, equipment, and chemicals, and the screens are not cheap. If you've never done this before (as it sounds), this is not a good first project.

You should either take your CMYK to a silkscreen shop, or print your image to iron-on transfer paper on an inkjet printer.

Films for silkscreen are typically positive-image, right-reading emulsion-up, 65LPI or coarser. If you don't know what that means, you probably should not be taking on this project ...
 05/16/2009 05:43:02 PM · #12
I've only done silk screening once, but it was not in full color. It was simply take a photo, turn it completely black and white using threshold/levels, and I did expose it onto the silk screen and so forth.

But it sounds like a full colored one is really complex.

I am aware of the overlapping and stuff, which is what my teacher said is very difficult to do. I found out something but I'm not entirely sure this will work, couldn't i just use the filter>pixelate>halftone in Photoshop? If i do this I can see the angle and frequencies.

Message edited by author 2009-05-16 17:46:22.
 05/16/2009 06:21:45 PM · #13
Originally posted by cujee:
couldn't i just use the filter>pixelate>halftone in Photoshop? If i do this I can see the angle and frequencies.

No, the screen settings are in the Output panel of Photoshop's print dialogs. You must know the correct settings or you're wasting your time.



05/16/2009 07:36:43 PM · #14
Originally posted by scalvert:
Originally posted by cujee:
couldn't i just use the filter>pixelate>halftone in Photoshop? If i do this I can see the angle and frequencies.

No, the screen settings are in the Output panel of Photoshop's print dialogs. You must know the correct settings or you're wasting your time.



ohh i see, how do you get to that halftone screen? I'm starting to get this junk, so is there a way to find out what angle and frequency you need for each channel before printing? When i silk screened the first time all i did was align the two photocopies by eye, but i'm assuming because there's going to be 2 for each channel, it'll be way more difficult to register the images.

Edit: Nevermind, i know where the halftone screen is.

Message edited by author 2009-05-16 19:41:23.
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