Process Color File Prep for Polyester Plate Lithography

1. Make your image in Photoshop, unfettered by strategic planning
   
2. Once it is pristine, change the mode to CMYK (you can do this first, if you want)
   
3. Adjust the midpoint of the entire image (Ctrl-L) to about 1.8:
   
   
   
   
   
   
   
4. Click on the "Channels" tab of the Layers palette
   
5. Select the Cyan layer, with all other layers off
   
6. Adjust the whitepoint (in Levels) of the Cyan layer (this is just to add a bit of contrast and get rid of some of the "noise" of the digital file, as hand printing is not as precise as offset):
   
   
   
   
   Before level adjustment
   
   
   
   
   After level adjustment
   
   
7. Continue this with each channel
   
   
8. Click on the "CMYK" channel again; the image should have decidedly more "punch" than it did a few minutes ago.
   
   Use your judgement. This is not an exact science and could be based on the lunatic ravings of an instructional technician.
   
   
9. Select Cyan channel
   
10. Convert to Grayscale
    
11. Print as usual (see Polyester Plate Lithography if you have questions), being careful to adjust angle for each color:
    
    Black / Darkest Color: 45°
    Cyan / Next Lighter: 15°
    Magenta / Next Lighter: 75°
    Yellow / Lightest: 90°
    
    
12. Repeat for Magenta, Yellow, and Black plates