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Presentation and Formatting: Screen to CMYK

File formats

Screen captures are low resolution RGB images that typically show a feature of a software program's user interface. They typically mix graphics and text, and possibly also images. Accordingly, many of our recommendations for photographs and illustrations don't apply. In particular, there are differences in sizing and scaling the image and in converting it to CMYK.

File format -- TIFF, not JPEG

To preserve the quality of text and the appearance of small user-interface elements, only lossless compression should be used. TIFF is the best choice for prepress (with LZW compression). JPEG compression will almost always degrade this sort of image and should not be used.

Size and scaling

If you resize screen captures in Photoshop, they will usually become less clear, particularly if you reduce their size. If you need to upsample them in Photoshop (perhaps to layer with other imagery) andy you wish to preserve the original appearance of each pixel, consider using "Nearest Neighbor" interpolation instead of the higher-quality "Bicubic" and restrict yourself to multiples of 100%. From the Image -> Image Size... dialog:

It is often useful to set the resolution of the image without resampling it. This will allow you to place it at its final size without having to scale it in your layout application. (Personally, I find that showing screen captures at 150ppi makes them look sharp without being too small.) Use Photoshop's Image -> Image Size... command, but turn off the "Resample Image" option:

Our usual practice is to check for low-resolution images and warn the designer / client if any are found. This can sometimes delay a job. If your job will be including screen captures at less than 200ppi, please mention this with your job instructions; it would also be helpful if you noted which images are screen captures.

Conversion to CMYK

RGB images must be converted to CMYK for traditional or digital offset printing in color. (Just convert to grayscale if you're printing in black only.) However, the default conversion used in the RIP or by Photoshop blends cyan, magenta, and yellow ink along with black to make shades of gray. This is appropriate for photographs, but can make screen captures look muddy, particularly any text.

To avoid this, Photoshop can be instructed to use as much black as is possible when converting the RGB screen capture to CMYK. Here's how to do this in Photoshop 7 (screen captures here are from Windows XP):

  1. Open the Color Settings dialog box from the Edit menu
  2. Change the working RGB color space to "sRGB IEC61966-21"
  3. For the working CMYK color space, select "Custom CMYK..."

    This will open a second dialog box. (Max GCR for screen captures will not be listed; we're about to create it.)
  4. In this Custom CMYK dialog, the most important setting is to set the Black Generation to maximum:

    I named this CMYK setup "Max GCR for screen captures." If you know that you will be printing on uncoated paper, you can choose those inks instead. If you know that the paper you will be printing on is very absorbent, you may wish to increase the dot gain to reduce the amount of ink put on the paper.
  5. OK the Custom CMYK dialog to create the "Max GCR for screen captures" CMYK setup and use it as your working CMYK space.
  6. If you will be working with more than one screen capture, it's probably worth your time to save this color setup. Click "Save" and after entering a name and comment, you should see something like this:
  7. Open your saved screen captures (or paste them into a new RGB document) and convert to CMYK while this color setting is selected. Save as TIFF with LZW compression.

--Dave Brown, September 2003