Resampling – Adobe Photoshop CS4 User Manual
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USING PHOTOSHOP CS4
Opening and importing images
Last updated 1/10/2010
Screen frequency is the number of printer dots or halftone cells per inch used to print grayscale images or color
separations. Also known as screen ruling or line screen, screen frequency is measured in lines per inch (lpi)—or lines
of cells per inch in a halftone screen. The higher the resolution of the output device, the finer (higher) a screen ruling
you can use.
The relationship between image resolution and screen frequency determines the quality of detail in the printed image.
To produce a halftone image of the highest quality, you generally use an image resolution that is from 1.5 to at most 2
times the screen frequency. But with some images and output devices, a lower resolution can produce good results. To
determine your printer’s screen frequency, check your printer documentation or consult your service provider.
Note: Some imagesetters and 600-dpi laser printers use screening technologies other than halftoning. If you are printing
an image on a nonhalftone printer, consult your service provider or your printer documentation for the recommended
image resolutions.
Screen frequency examples
A. 65 lpi: Coarse screen typically used to print newsletters and
grocery coupons B. 85 lpi: Average screen typically used to print newspapers
C. 133 lpi: High-quality screen typically used to print four-color magazines D. 177 lpi: Very fine screen typically used for annual reports and
images in art books
More Help topics
Resampling
Resampling is changing the amount of image data as you change either the pixel dimensions or the resolution of an
image. When you downsample (decrease the number of pixels), information is deleted from the image. When you
resample up (increase the number of pixels, or upsample), new pixels are added. You specify an interpolation method
to determine how pixels are added or deleted.
A
B
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D