Raster

An image made of a fixed grid of pixels. Rich for photographs, unforgiving when stretched past its size.

A raster image is a census: this grid of pixels, each with its colour, counted once at one size. Within that size it holds what vectors cannot, the grain of a face, the noise of light, the accidents that make a photograph a document rather than a diagram.

Unforgiving when stretched because enlargement asks the grid for detail it never recorded; software can only guess, and guesses read as blur. The working rules follow: capture above the largest intended use, scale down, never up, and keep the master untouched. A raster resized destructively has testified; it cannot be re-asked.