Resolution

Image shows the Image Size dialog box in Photoshop and the resolution of 1`00 pixels per inch is highlighted.
Resolution is the number of pixels per linear inch in a digital image.

Definition:

Resolution is a measurement of the output quality of an image, usually in terms of samples, pixels, dots, or lines per inch. The terminology varies according to the intended output device. PPI (pixels per inch) refers to screen resolution, DPI (dots per inch) refers to print resolution, SPI (samples per inch) refers to scanning resolution, and LPI (lines per inch) refers to halftone resolution.

Often images are referred to as high resolution (hi-res) or low resolution (low-res). High resolution would be an image intended for print, generally having 300 samples per inch or more. Low resolution refers to images only intended for screen display, generally having 100 pixels per inch or less.

Scanner and digital camera manufacturers often refer to two different types of resolution when listing product specs: optical resolution and interpolated, or digital, resolution. The optical resolution is the true measurement of resolution that the output device can capture. Interpolated, or digital, resolution is acquired artificially.

With the rise of mobile another term has crept into the the resolution discussion. You may have seen "DP" used when discussions break out around imaging for mobile. DP refers to what is called a "Device Pixel". This is the the pixel on your smartphone. The problem is, depending on manufacturer, they are not the same size.

Using the iPhone as an example, a "retina display" has 2 to 3 times as many pixels on the screen as a computer screen. This means, there are two or three pixels where there is just one on your computer. We have a rather involved discussion about this in "All About Pixels".

 

Updated by Tom Green

Graphics Glossary

 

Also Known As: rez, res, dpi, ppi, lpi, spi, hi-res, lo-res, low-res

Common Misspellings: rezolution, resolusion, resulution, resolition