Want to make your digital images really pop in print? It’s time to get back to the Photoshop training basics! In the first two installments of our series on getting the most from your digital images in Photoshop, we focused on some basic scanning advice and provide a bit of background on highlights, shadows, and contrast. Understanding those topics will give you a good grounding. While the program may change from version to version, the essentials of Photoshop training for print production hold true.

With that in mind, lets touch on the topics of selective color adjustment, sharpness, and image resolution …

Selective Color Adjustment

Selective color adjustment is one of the last steps in completing a color separation. Selective color adjustment allows the user to adjust CMYK values within colors. For example; reducing the cyan value in the red without affecting any other colors such as blues and yellows.

Up to this point we adjusted the white, black, gray, and contrast of the image. These four steps in the process will change the appearance of the image dramatically. After adjusting these four steps, the colors in the image should typically improve. If however they do not, selective color adjustment is necessary.

To understand selective color adjustment, you’ll need to understand wanted and unwanted colors. For example; the wanted colors in red are magenta and yellow. The unwanted color is cyan. Cyan and black control saturation in red. The only way to brighten a red that consist of solid magenta and yellow is to reduce the cyan and/or black.

Some scanners provide you with this capability directly in the scanner software. If your scanner does not, Photoshop has a selective color adjustment that also allows correction in whites, blacks, and grays.

Look Sharp

Sharpness can either be applied on the scanner or after the initial scan. It’s a good idea to apply sharpening after the final tone adjustments. Unsharp masking (USM) as it is often refered to, works by examining where light and dark gray levels meet. The process then creates a fringe effect between the light and dark gray levels.

Think about an image of a person wearing a white shirt and black slacks. The point where the shirt and slacks meet is a prime example of where USM will apply a fringe effect. The white area will take on a slight white line where it meets the dark slacks. The dark area will take on a black line, creating the illusion of sharpness. Because you’ve adjusted the tones throughout this process, it’s best to apply USM when the tones are close to their final setting.

Specify the Right Resolution

Choosing the proper resolution before making the final scan can save valuable time and storage space. The rule of thumb is that the resolution should be 1.5 - 2 times the line screening. For example; an image printed at 150 LPI should be scanned in at 225 - 300 pixels per inch. You may have read that anything more is a waste of time. In most cases this is true, however, not all images are created equal! Most high end scanners allow the operator to scan at a high res mode to improve overall quality.

Images with lines or patterns can benefit from a higher input resolution. For example; the vent of a monitor that is made up of horizontal lines may look jagged with the normal suggested resolution. Increasing the resolution to 350 pixels can reduce the jaggedness.

This section on selective color adjustment, sharpness, and resolution originally appeared in The Photoshop Plug-Ins Book.

Photoshop Training Links