Photoshop & Rich Black
Not all black is created equal, especially when you are preparing artwork for print.
Using 100% black on small objects such as body copy, fine keyline borders, and other delicate details is recommended. But when you have a large area of solid black or very large black type, 100% black alone can sometimes look less substantial when printed.
The reason comes down to how process inks work.
What Makes a Black "Rich"?
Process inks are translucent. They let some light pass through, much like a color filter. That light is reflected back from the paper, which can make a large area of 100% black appear less dense than you might expect.
To increase the richness of the black, you can add additional process color to the black ink. In prepress, this is commonly referred to as rich black.
Rich blacks are created by adding varying amounts of process cyan, magenta, and yellow to black. The right combination can depend on the design, printing process, press conditions, paper, and other production requirements.
At Castle Press, our typical standard rich black is:
C = 40% | M = 40% | Y = 40% | K = 100%
That doesn't mean 40/40/40/100 is the right rich black formula for every printing situation. Ink coverage, paper stock, and color requirements vary by project and production conditions. Adobe likewise recommends using a CMYK working space that matches the intended output conditions.
Watch for Mismatched Blacks in Images
A common problem occurs when you place an image over a rich black area in a page layout, and the image itself contains a black background.
The black background of a scanned image may not be 40/40/40/100. It may look like a match on your monitor, but if the CMYK values differ, the difference can become noticeable when you produce the printed matter.
One way to check is to open the image in Photoshop and use the Info panel to inspect the color values. Position the cursor over the black area, and Photoshop will display the color information for that location. In a CMYK image, you can see the percentages for cyan, magenta, yellow, and black.
If you are working with an RGB image, don't automatically convert it just because you're using it in a print project. The appropriate color workflow depends on the intended output and the printer or press specifications. Adobe's current Photoshop guidance recommends editing an image in RGB when appropriate and converting to CMYK at the end of the editing process when preparing the image for CMYK printing.
How to Match the Black in Photoshop
If the black in an image doesn't match the rich black in your layout, can you are correct it in several ways.
One approach is to use a color adjustment in Photoshop to modify the black area while watching the CMYK values in the Info panel. The goal is to bring the image's black closer to the rich black used in the layout.
You can also select the black area in Photoshop and fill the selection with the matching rich black percentages. A Color Range selection with a relatively low fuzziness setting can help isolate a black background or other areas with similar colors. Photoshop's current tools support using Color Range selections as masks for targeted, non-destructive adjustments.
For more flexible editing, Photoshop's current adjustment-layer workflow allows you to make targeted color changes without permanently altering the original image.
Another option is to adjust the rich black in your page-layout program to match the black used in the image.
The important thing is consistency. When a large black background in a layout meets a black background inside an image, matching the underlying color values can help prevent a visible difference between the two areas.
Because color appearance can vary across monitors, applications, printing processes, and papers, keeping color profiles and color management consistent throughout the workflow is also important. Adobe recommends embedding color profiles so that other applications can interpret the image's color information correctly.
Have more questions about an upcoming printing project? Contact us!
