The Difference Between DPI and PPI

Digital camera resolution

A pixel is not created with fixed size. Instead, its three RGB ingredients can recreate the same - coloured pixel be it an inch square or a metre square - you set the pixel size to match the intended output. Using photoshop's Image Size dialogue box, pixel size can be set to any size, usually 72 per inch for screen viewing or 300 per inch for printing. The number of pixels in the image remain the same, but those pixels can be made physically bigger or smaller. At an inch square, pixels will look like tiles from a giant mosaic and would be a poor photographic illusion. The smaller your pixels are, the more invisible they become and the more realistic a printout willbe. All digital cameras create images with pixels set at 72 per inch, but if you made them smaller, for example 300 dpi, the printout will be physically smaller, but of a much higher quality

Scanner resolution

The term resolution is just another way of describing potential image quality. Like the variously sized sensors found in digital cameras, flatbeds are also sold on their basis of their resolution. Scanner quality isn't described in megapixels or in pixel dimension, but by the ability to capture pixels across one linear inch. Thus a 600 pixel per inch ( or ppi ) scanner will create a 3600x2400 digital image from a 6x4 in print. Even budget 1200ppi scanners create more data than is really needed and anything over 2400ppi is overkill for desktop photo printing.

Printer resolution

Most printers can be operated in lower-quality mode for making rough prints to keep your cost down. A printer resolution of 360 dot per inch (dpi) will drop less dots of ink on the receiving paper no matter if your image is a high resolution file. Best photo quality is made using 1440 or 2880 dpi, but expect each print to take a lot longer to print and more ink to be used. Never select the High speed setting for photographic quality results- some printer resolutions may become unavailable, as they are deemed inappropriate for the paper.

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