Printing digital images also has an often-neglected parameter. It's called line frequency and is a measurement of how many lines/inch the image is rasterized at for printing. Unless you're using a continuous-tone printer like a dye sublimation rig, the image will be rasterized. Regardless of the resolution or size of the image in pixels you will need to use the proper line frequency when it's printed or it won't look good.
This is especially important for grayscale images. There you want to have as many shades of gray as is practical, but you have to trade off gray shades with line frequency to find the correct balance.
To find the resuting gray shades given a certain line frequency is found by:
(Printer DPI/Line Freq.)^2
a 300 DPI Laser Jet at a line freq. of 53 (default for this printer in many DTP apps) = 32 shades of gray. You can see how as you increase the line freq. for a sharper image, you are trading off gray shades which is equally important
Typical newspapers may run line frequencies from 50 - 100. Magazines will run 100 - 200 usually. You can see where a high resolution printer is a necessity
This isn't an issue if you're starting out. And there are many online places where you can upload your digicam files and have them printed on silver halide paper, the same stuff film negatives are printed on, and extremely stable compared to dye sub