In an effort to see the affect of various image PPI and printer DPI settings I created five image test files and printed them to spool files (not to paper). Each image file consists of simply alternating black and white pixels in a 4 by 6 inch image, but at various PPI settings.
|Image File||Image PPI||Image Pixels||Image Size||2880 DPI||1440 DPI||720 DPI||360 DPI|
|4x6 Printer Dots||99,532,800||49,766,400||12,441,600||3,110,400|
I expected that at a given DPI setting the spool file size should be the same irrespective of the image PPI. Clearly it isnít. At 2880 or 1440 DPI it varies from 8MB to 23MB. And at 180 PPI various DPI settings produce spool file sizes from 32KB to 23MB. Note that this image was selected to maximize resolution testing. It only contains two tones.
With a more traditional photo image the spool file size was essentially consistent at all PPI settings. 40MB at 2880DPI, 24MB at 1440DPI, 11MB at 720DPI, and 3MB at 360DPI. Using an image with mixed photo, text, and resolution patterns, the spool file size varied between 2 and 64MB (in the Windows printer status window) based in the image PPI, at either 1440 or 2880 DPI. Clearly there are some dynamics in the RIP software that I donít understand yet.
Rags Int., Inc.
204 Trailwood Drive
Euless, TX 76039
April 19, 2004
This page last updated on: Thursday April 12 2007