Digital Photo Printing

What can I expect from an Inkjet printer ?

Digital images have pixels, film has grain and digital printers have dots.

All of these limitations have one thing in common -- human visual acuity and color perception. What matters most is what we can see.

For digital images, it is easiest to think in terms of the following relationships:
  • Camera - Image size in pixels (like 3888 x 2592 for the Canon 40D)
  • Computer - Print image resolution in PPI (pixels per inch) when printed
  • Printer - Printing resolution in DPI (dots per inch) on the photo paper
It is easy to see that an image configured as 200 PPI and sent to a printer with 1200 DPI resolution, will print an array of 6x6 printer dots for every pixel in the image. This would mean that only 36 ink dots are available to display the printed color of any pixel in the image.

What is not so obvious, is the relationship between printer spatial resolution, print color resolution, image pixel dimensions, human visual acuity and desirable viewing distance. All these factors are dependent on each other and combined, they decide the range of what is reasonable to print.