Effective Resolution of Images

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Effective Resolution of Images

Applies to: QuarkXPress 8 – Mac OS 10.4 and 10.5

 

Problem Description: When I have a raster image, such as a JPEG or TIFF, selected in QuarkXPress 8, there is a new value listed in the lower right hand corner of the Measurements palette called Effective Image Resolution. However, I can’t seem to modify the value that is displayed. What is this for and why can’t I modify its value to set the image to the resolution I want?

 

Background: When an image is created or scanned, the creation or scanning software sets the number of pixels per inch (ppi) for the image. When you scale the image up or down in QuarkXPress after importing it, the resulting resolution of the image decreases or increases according the amount you have scaled the image. The resulting resolution is called the effective image resolution. As an example of how this works, if you import an 2”x 2” image that has a resolution of 150 ppi, and scale it down to fit a 1” x 1” box, you are effectively doubling the number of pixels that occur over a one inch distance, which results in an effective resolution of 300 ppi. If you import the image and scale it up to twice its size (4” x 4”), you are effectively cutting the number of pixels per inch in half, resulting in an effective resolution of 75 ppi. While effective resolution changes have always occurred when you scale an imported image up or down in any version of QuarkXPress, QuarkXPress 8 is the first version where this value is actually displayed.

 

Solution: The Effective Image Resolution value in the Measurements palette only reflects image resolutions that are the result of a scaling operation. You cannot select the value in the Measurements palette itself and set the effective resolution. Rather, the value shown is the result of any scaling operations you have already applied to an image.

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Topic Information
  • Topic #: 30026-1443
  • Date Created: 11/20/2012
  • Last Modified Since: 09/05/2016
  • Viewed: 1694