This check makes sure that pixel image are placed at a size so they output at a minimum of 250 PPI (pixels per inch). This check also allows the GreenLight user to allow exceptions to this rule.
‘Links’ are extra files which are referenced by an InDesign document. Although links can be other file types, such as text, typically links refer to images placed into an InDesign document.
When placing pixel images onto an InDesign page their original resolution (how many pixels the image has over a given measurement) becomes their Actual PPI.
Scaling the image up or down on the InDesign page does not alter the original linked image but does affect the PPI when outputting. The resulting resolution is referred to as the Effective PPI. Increasing the scale of an image causes the Effective PPI to go down; decreasing the scale causes the Effective PPI to go down.
Scaling the image up so that the Effective PPI drops below 250 will result in less than optimal output.
Aside from file size issues, having too many pixels is rarely a problem. Having too few, however, can mean a loss of definition and image quality.
There may be times when an image is so good or unique that it needs to be used despite having a low effective resolution. Also a soft image e.g. a natural landscape and clouds can often be output at a lower resolution but still with good image quality. In either case, or when you simply don’t have an alternative, you can mark the image as OK when prompted by GreenLight.
Fix this problem by sourcing higher resolution version of the same images, using an alternative image, or by marking the image as OK.
Tip: It is possible to switch on an Effective PPI column in the Links Panel. (Window > Links)
Adobe links and graphics help
