halftone


Also found in: Dictionary, Thesaurus, Medical, Financial, Wikipedia.

halftone

Art a tonal value midway between highlight and dark shading

halftone

[′haf‚tōn]
(graphic arts)
An engraving used in printing to reproduce photographs and drawings that contain continuous tones, that is, grays (middle tones or halftones) in addition to black and white; preparation involves photographing the artwork through a screen.

halftone

(graphics)
The reproducion of greyscale images using dots of a single shade but varying size to simulate the different shades of grey.

Laser printers that cannot print different sized dots, halftones are produced by varying the numbers of dots in a given area.

This process is also used to produce a black and white version of a colour original using shades of grey in place of colours.

See also device independent bitmap.

halftone

In printing, the simulation of a continuous-tone image (shaded drawing, photograph) with dots. All printing processes, except for Cycolor, print dots. In photographically generated halftones, a camera shoots the image through a halftone screen, creating smaller dots for lighter areas and larger dots for darker areas. Digitally composed printing prints only one size of dot.

In order to simulate variable-sized halftone dots in computer printers, dithering is used, which creates clusters of dots in a "halftone cell." The more dots printed in the cell, the darker the gray. As the screen frequency gets higher (more cells per inch), there is less room for dots in the cell, reducing the number of shades of gray or color that can be generated.

In low-resolution printers, there is always a compromise between printer resolution (dpi) and screen frequency (lpi), which is the number of rows of halftone cells per inch. For example, in a 300 dpi printer, the 8x8 halftone cell required to create 64 shades of grays results in a very coarse 38 lines per inch of screen frequency (300 dpi divided by 8). However, a high-resolution, 2400 dpi imagesetter can easily handle 256 shades of gray at 150 lpi (2,400 / 16).

PRINTER RESOLUTION & MAXIMUM SCREEN FREQUENCYShades of     Gray or  --At printer resolutions--Cell  Colors  300 dpi  1200 dpi  2400 dpi4x4    16    150 lpi   300 lpi   600 lpi

  8x8    64     38 lpi   130 lpi   300 lpi

 16x16  256     19 lpi    75 lpi   150 lpi



Analog Vs. Digital
The analog world of commercial printing prints dots in varying sizes. The digital world prints in grids of dots. Increasingly, digital printers use techniques that overlap dots to achieve greater variability in dot sizes.
References in periodicals archive ?
14] proposed an image hashing scheme using the halftone mechanism, which can be applied in the field for image authentication and retrieval.
Esta forma de ordenar los elementos de la matriz de umbral produce una imagen halftone tipo AM.
Halftone algorithms can be essentially divided into two basic groups.
The factor "w" describes the optical spread function of substrate relative to the spatial frequency of halftone dots.
A halftone image could be reproduced in gray scale by arranging the black and white pixels in a grid.
There is a valid rule in halftone reproduction which says that the size of the printed screen elements increases with the increase of the halftone value.
The ink's printing characteristics make it a perfect substitute for process black inks in halftone and other applications in which a strong black is required.
Writing of his partiality to halftone color reproductions of food and flowers from the 1890s to the 1950s, he opined in a text celebrating a new, denim-upholstered sofa that "beauty that issues from such banal and especially accessible sources seems a perfect metaphor for the American experience to an upwardly mobile son of immigrant parents, .
Willoughby, Ohio - Kase 908 sidewall printer for dairy cups and containers is a nine-color unit that can reproduce line, halftone, or process printing.
Promising faster halftone imaging and better quality for newspaper photos at a cost comparable with that for existing technology, the University of Rochester, in N.
A screen is defined by conceptually laying a uniform rectangular grid of halftone cells over the device pixel array (Adobe Systems I.
The new halftone dot technology divides the conventional round dot into thin concentric rings that limit ink film thickness on the offset plate.