it lessens the intensity of the colors. By changing the opacity you'll see more of the base paper show thru! HTH!
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Katie - owner of DesignerDigitals
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My Blog : Documenting + Designing
Camera: Nikon D700 with Speedlight SB-600
Lenses: 16-35mm F4, 24-70mm F2.8, 70-200mm F2.8
Software: Adobe PSE3 and CS3, Illustrator CS3
computer platform: Mac