What is halftone effect?

[chung]

Hello

I did my homework looking for the answers,but still I only half understand.

Thank you for any explanation.

Koo Young Chung

 

[Ian Grant]

It used to be when a photo was convered to dots for printing. Halftone gave the impression of tones as opposed to Line film which gave just Black or White.

I once had some Kodak film that gave direct half tones. In other cases you exposed throgh a screeen onto line filme then made the plates. These days it's digital direct to plate mostly.

Ian

 

[lxdude]

I once had some Kodak film that gave direct half tones.

Ian

Could you expound a bit on that?

 

[rmolson]

The half tone effect is the converting of continuous tone images to dot images that can be printed on presses. Which are capable only of a single tone with no shading A typical newspapers used screen ruling from 65 to 110lines per inch depending on the press and the paper it was to be printed on .But now with computer I have no idea of ho w they make the dot pattern ,It use to be either round ,square or elliptical Originally it was used in reproduction as the only way to get a continuous image etched into metal .It is still used in Lithography ( offset) for large volume printing like newspapers and magazines a simple magnifier will show the dots on the paper. The Kodak film with a built in screen was called Auto Screen and usually available in 133 line. Basic exposure established the main image and a non image flash boosted the shadows, a common practice with glass and contact screens High end scanner do the same thing with lasers. They convert continuous tone images to dots of varying sizes that represent the tonal scale of an original .

 

[lxdude]

Thanks for the information!

 

[Steve Smith]

It used to be when a photo was convered to dots for printing.

And still is. Look very closely at a newspaper photograph.

Hover your mouse over the densities to the right of the second image down this page: http://www.ted.photographer.org.uk/photoscience_halftones.htm


Steve.

 

[Leigh B]

The halftone process produces a range of gray tones in an image that's printed only with black ink.

The effect is achieved by using an array of small dots (think pixels), each of which can go from extremely tiny (not there = white) to solid black.
The larger the dot, the darker the gray tone.

The process is still in use for newspapers and magazines, and other applications of modest quality.
Look at a photo in a newspaper with a magnifying glass to see the dots.

It can also be used for printing full-color photos, using a similar technique but with a separate half-tone mask for each of the subtractive primary colors,
Cyan, Magenta, and Yellow. Because the combination of these three does not produce a clean black, black ink is also used, hence the CMYK designation.

There's a related black-and-white process of higher quality called Duo-Tone.
It still uses a dot matrix, but two masks set at an angle to each other, which yields better fidelity.
This process is commonly used to print high-quality photographs in books.

- Leigh