halftone


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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 ?
Please Note: Formica and the Formica Anvil Logo are registered trademarks and Formica Forever (TM), the Formica Anvil Logo Forever, the Formica Forever (TM) ellipse logo, Ellipse (TM), Endless (TM), Dotscreen (TM) and Halftone (TM) are the trademarks of The Diller Corporation.
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.
The voltage change on DD ([DELTA]U=300V), the printed screen dots will oscillate: in the area of 10% halftone value ([DELTA]d=6,82 [micro]m), in the area of 20% halftone value ([DELTA]d=8,10 [micro]m) and in the area of 30% halftone value ([DELTA]d=6,97 [micro]m).
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If the halftone screen that we are developing rapidly changes its shape through the grayscale, we can increase the number of discrete gray levels in this 2D simulation model in the course of experimenting.
Mark Samworth, vice president of technology, said the basic geometry of the conventional halftone dot has hardly changed since the inception of offset-litho around the late 19th century.
Corel and IKONICS Corporation today released a new, joint solution enabling users to quickly and easily convert simple line images into photographic quality halftone images.
NASDAQ: CREO, TSE: CRE) (`Creo') is pleased to announce that CreoScitex showcases a range of professional desktop, continuous-tone and halftone contract, and imposition proofing innovations at Drupa 2000, the world's largest trade show for the printing industry, underway in Dusseldorf, Germany, May 18-31.
Developed in partnership with Enovation Graphic Systems (A Fujifilm Company) to meet the requirements for creating spot color libraries for the Fujifilm FinalProof GxT digital halftone proofer, PerfectPalette tackles the challenge of getting the right spot color simulation the first time, avoiding multiple adjustments to make spot colors match the target from prepress to the pressroom.
Latran Technologies, a manufacturer of digital halftone proofing equipment, and Esko-Graphics, a leader in integrated packaging pre-production systems, have entered into a distribution agreement for the USA and Canada.
Combining the highest quality equipment with over 10 years of color management experience, the company staff provides a full service color management solution with services including "administered" color management, remote proofing and Vendor Neutral Proofing(TM) on the Polaroid PolaProof 2230 digital halftone proofing device.