Thoughts from this side of the camera.
Recently a client asked me to give them a digital photo sized at 300 pixels. This request is meaningless. When we speak of pixels we usually mean the number of pixels in an inch. Without knowing the size of the reproduced image, it is impossible to supply the requested photo. Example: Asking for a photo 300 pixels at 10 inches makes more sense. By adding the other dimension one can calculate the file size. (8 x 10 inches at 300 pixels creates a file size of 7.2 megs.) This will print very nicely on most glossy stocks like magazines etc. It is overkill for newspaper reproduction, however. Knowing all the details like where and how large the photo will be used insures the proper file size necessary for good reproduction.
Some guidelines are: Glossy Stock Color Printing – 300 pixels per inch at the printed size. Newspapers require around 200 pixels per inch at the printed size.
Below is an example of two same sized photos with different pixel dimensions.
Notice the difference in how the images appear. Size matters in in Pixels.