Suppose you wish to publish an image captured by a 12-megapixel camera. This camera creates files with a resolution of 4288 by 2848 pixels. To determine the print size of this file (width by height), divide the pixel dimensions by the resolution. Typically, the resolution will be 300 dpi (dots per inch), which produces a print with a highly attractive appearance. Ideally, printouts should have a dpi between 100 and 360 (anything below this will start to look ugly because the pixels would be highly visible) (more dpi at this point will not be seen by the naked eye). Images can be reproduced at a resolution of 200 dots per inch with minimal loss of visible information. Divide 4288 by 300, which represents the longer of the image's two pixel dimensions (the intended dpi of the image). This will result in the longer dimension of the printable image size.
The length size of a 12-megapixel camera with a 3/2 format will have 4288 pixels per inch (ppi). When 4288 ppi is divided by the photo's 300 ppi, the answer is 14.29 inches, which is how long the photo will be in inches. This is the formula: Width dimension of the photo multiplied by the specified resolution equals the width of the photo as printed when the file leaves the camera.
The relatively new 4/3 format permits the production of an 8 10 print with minimal cropping, as well as a double-page magazine spread. This is a "open" format, therefore all lenses are compatible with any 4/3 manufacturer bodies.
Changing the image's resolution (dpi) will result in a different output size.
print. If the identical 8 megapixel image was printed at 200 dpi, the finished dimensions would be 3265 divided by 200, or 16.36 inches on the long side and 12.24 inches on the short side.
The short dimension divided by the required resolution (300) equals the resulting size of the image's short side when printed from the camera file.
It is simple to enlarge or reduce the image size from the native file size, and Photoshop's tools provide the digital darkroom a great deal of power.