Half-tone

From Nikonians Wiki

Half-tone is the method of reproducing continuous tones in commercial offset litho, and in most laser printers.

The continuous tones are replaced by black or coloured dots, of varying size, on a grid. At normal viewing distance, the dots appear to the eye to be smooth tones of colours. Generally, all colours are made up of Cyan, Magenta, Yellow and Black (CMYK), although advanced printing systems now use six or more colours, to enhance the gamut.

Half-tone resolution is in Lines per inch LPI. Because of the way half-tone works, the lines per inch achievable is dramatically less than the resolution of the printer, in dots per inch (dpi), if 256 values are to be achieved.

Typical values

When preparing images for half-tone reproduction, they must be oversampled, typically by 2x, so that for standard 150 lpi magazine reproduction, an image of 300 pixels per inch (ppi) at the desired size should be supplied. In practice, values of 1.5 and 1.25x oversampling can produce fine results, as long as no geometrical patterns are included, which might cause moiré.

• This page was last modified on 28 December 2008, at 14:33.
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