Print images to a commercial printing press

From Photoshop, you can prepare image files for offset lithography, digital printing, gravure, and other commercial printing processes.

Generally, your workflow depends on the capabilities of the prepress facility. Before you begin a workflow for commercial printing, contact the prepress staff to learn their requirements. For example, they may not want you to convert to CMYK at any point because they may need to use prepress-specific settings. Here are some possible scenarios for preparing your image files to achieve predictable printing results:

• Work entirely in RGB mode and make sure that the image file is tagged with the RGB working space profile. If your printer or prepress staff use a color management system, they should be able to use your file’s profile to make an accurate conversion to CMYK before producing the film and printing plates.

• Work in RGB mode until you finish editing your image. Then convert the image to CMYK mode and make any additional color and tonal adjustments. Especially check the highlights and shadows of the image. Use Levels, Curves, or Hue/Saturation adjustment layers to make corrections. These adjustments should be very minor. Flatten the file if necessary, then send the CMYK file to the professional printer.

• Place your RGB or CMYK image in Adobe InDesign or Adobe Illustrator. In general, most images printed on a commercial press are not printed directly from Photoshop but from a page-layout program like Adobe InDesign or an illustration program like Adobe Illustrator. For more information on importing Photoshop files into Adobe InDesign or Adobe Illustrator, see Adobe InDesign Help or the Adobe Illustrator Help.

Here are a few issues to keep in mind when you work on an image intended for commercial printing:

• If you know the characteristics of the press, you can specify the highlight and shadow output to preserve certain details.

• If you use a desktop printer to preview the appearance of the final printed piece, keep in mind that a desktop printer cannot faithfully replicate the output of a commercial printing press. A professional color proof gives a more accurate preview of the final printed piece.

• If you have a profile from a commercial press, you can choose it with the Proof Setup command and then view a soft proof using the Proof Colors command. Use this method to preview the final printed piece on your monitor.

Set output options

If you are preparing your images for commercial printing directly from Photoshop, you can select and preview a variety of page marks and other output options using the Print command. Generally, these output options should be specified only by prepress professionals or people knowledgeable about the commercial printing process.

For information on the Include Vector Data option, see Print vector data.

Print separations from Photoshop

When preparing your image for prepress and working with CMYK images or images with spot colors, you can print each color channel as a separate page.

Prepare an image with spot channels for printing from another application

Create a color trap

A trap is an overlap that prevents tiny gaps in the printed image caused by a slight misregistration on press. Contact your service provider before you do any trapping. In most cases, your print shop determines whether trapping is needed. If so, the print shop staff will tell you what values to enter in the Trap dialog box.

Trapping is intended to correct the misalignment of solid colors. In general, you don’t need traps for continuous-tone images such as photographs. Excessive trapping may produce an outline effect. These problems may not be visible on-screen and might show up only in print. Photoshop uses standard rules for trapping:

• All colors spread under black.

• Lighter colors spread under darker colors.

• Yellow spreads under cyan, magenta, and black.

• Pure cyan and pure magenta spread under each other equally.

Determine scan resolution for printing

You can use a number of techniques to determine the resolution at which to scan a photograph. If you are scanning photos to be printed, and you know the exact size and the printing screen frequency, you can use the following techniques to determine the scanning resolution. Often it is easiest to scan at your scanner's maximum optical resolution and then resize the image in Photoshop later.

Estimate scan resolution

You can determine the resolution for your scan using the original and final image dimensions and the resolution of your output device. Scan resolution translates into image resolution when you open the scanned image in Photoshop.

Calculate the file size before scanning an image

You can create a dummy file to predict the file size needed for the final output of your scan.