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 ?
where [a.sub.t] is the predicted area coverage and [R.sub.[lambda],m] is the measured reflectance values of the halftone patch.
[14] proposed an image hashing scheme using the halftone mechanism, which can be applied in the field for image authentication and retrieval.
donde h es la imagen halftone y tn es la matriz de pantalla que se genera usando la matriz de umbral aplicando (2).
Digital Halftone originated in the 60th with the need to reproduce images for binary displays.
The light that enters the substrate between the halftone dots can scatter laterally within substrate before returning to the surface as a part of reflected light.
These wonderful publications exemplify how the halftone created "a new medium, in which photographs and text worked together to create a third meaning." (2) Now sharp, documentary-like pictures confirmed the text and showed California as a viable place to live, while always promoting its lyric inland landscapes and ruggedly beautiful coastline.
Bahram Javidi have combined the 2-D halftone image and barcode by slightly shifting the positions of the arrangement halftone dots.
The new IBM Infoprint 4100 family of printers offers a combination of 19.5-inch width, halftone image quality and high speed.
The new CNC-K-908 from Kase Equipment is described as a versatile sidewall printer for high-quality line, halftone, or process work.
Sharp Intelligent Image Segmentation (SIIS) is a high-speed image processing technique designed to keep character images crisp and halftone images smooth within the same document.
Ricoh's VT6000 digital duplicator incorporates a newly developed thermal head with a highly sensitive master that delivers sharper, clearer lines, letters and halftone images at 600 dpi resolution.
Not only does this model offer Mirror Print and Negative Print, it adds features like patent pending X-ACT (Xante's Accurate Calibration Technology), Halftone Calibration Technology, Enhanced Screening, and Densitometer Support.