Digital Prints

Resolution
This seems to be the single most confusing word in all of the digital imaging world. And
it doesn’t help that there are different terms and definitions for camera resolution, scanner
resolution, monitor resolution, file resolution, and printer resolution. Since this is a
book about printing, let’s concentrate on the last two: file and printer resolution.
File or Image Resolution
In basic terms, the resolution of a digital, bitmapped image is determined by how many pixels
there are. This is called spatial resolution. If you have a scanned image and can count 100
pixels across (or down) one inch of the image (remember, bitmapped images actually have
no physical size until they are rendered into a tangible form; at that point, you can measure
them), then the resolution is 100 pixels per inch or 100 ppi. Technically, it’s pixels per inch
(ppi) when you’re talking about image files, monitors, and cameras. But it’s dots per inch
(dpi) when it comes out of a printer because, if it’s an inkjet, the printer’s software translates
the pixels into tiny little marks or dots on the paper (see “Dots, Drops & Spots” box).
An image’s resolution will, in part, determine its quality or the degree of detail and definition.
The more pixels you have in a certain amount of space, the smaller the pixels, and the
higher the quality of the image. The same image with a resolution of 300 ppi looks much
different—and better—than one of 50 ppi at the same relative output size (see Figure 2.5).
Figure 2.5 Image resolution affects detail and definition. Left: 50 ppi, Right: 300 ppi.
Chapter 2 ■ Understanding Digital Printing 41