Photoshop - The Key to Working with Black

Using process black on small objects such as body copy text and fine keyline borders is OK. But if you have a large background of solid black or very large black type, then the solid black may look washed out when printed.

All process inks are translucent. They allow light to pass through them, much like a color filter. The light is then reflected back to our eyes and the result is a washed out looking black.

To increase the “richness” of the black it is necessary to add additional color to the black. In prepress this is called “Rich Black” or “Undercolor Black”.

Rich blacks are created by adding amounts of process cyan, magenta and yellow to the black. The amount of CMY added can vary, based on many things, such as the design of the project, press conditions, and the paper the project is to be printed on.

The Castle Press standard rich black will depend on the press that your project will be printed on. For our lithographic presses the callout is C=30%, M-20%, Y=20% and K=100%. For digital the callout is C=60%, M=40%, Y=40% and K=100%. (A)

Now, a problem arises when you place an image with its own black background. The black background of a scanned image will not be 30-20-20- 100 or 60-40-40-100! It may look correct on your monitor but it isn’t.

An easy way to check is to set your color channels in Photoshop to be viewed in black & white. (B) Using the “Control” key and pressing 1,2,3, you can scroll through the channels and check the differences in density. (C)

To make the necessary adjustments, go to Image➔Adjust➔Selective Color. Using the sliders, adjust while watching the dot% in the Color palette. Continue to adjust until the scanned image background matches the rich black background. (D)

photoshop windows

GLOSSARY

Process Inks

Inks used in process color printing of full color illustrations and images. The colors used are cyan, magenta, yellow and black.

Translucent

Descriptive of a surface or object that allows light to pass through it.

Rich Black

Black that has percentages of cyan, magenta and yellow added to it to make black ink look richer in large solid areas.

Density

The perceived darkness of a substance, material or image caused by the absorption or reflection of light.



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