T-shirt designs

index color separation

“Separate Separation”- force the colors to appear as the way you want it to be
There will be circumstances where you want to eliminate a color (spattered dots) within a particular area for the reason it will spoil the color purity of that area.

I'm going to show you (with a demo) how to eliminate a color in an area in Index Color separation. Here are the steps...

This is the 8 colors index separated (index mode) image :

But I found that the gray dots spattered within the midtone purple area spoil the purity of the purple.

Don't solve by simply select the area with lasso and use color range to select the spattered gray dots, apply the color range to select the spattered dots and fill them with purple. (This is not the proper method, this will interrupt the "natural diffusion dither pattern" formed.)

Here is the correct method :

Open the original RGB image, index the image once more. Load the Color Table saved but this time set the Gray color in the Color Table to White (become 7 color Index separation). Continue index separation process. You will find that there is no more Gray Dots in the area. The purple looks pure.

Now I'm going to transfer the purified purple portion to the actual 8 color indexed file. Select the portion precisely with lasso or path tools, don't select the portion that looks incorrect because this 7 color index separation procedure is done purposely only to purify the purple portion. Drag and drop the selection into the 8 color indexed file. (The selection will land precisely at the place where it should be in Photoshop 3.0. For Photoshop 5.0, hold down "Shift"+"Ctrl" during drag & drop).

You can use this mothed more than once in a image until you are satisfied with the color distribuiton of the entire image.

Article by : John Lean
john@teedesign.com