The Halftone Process

Advanced Digital Photography

By Adam Butts

What is Halftone?

A halftone is the reproduction of an image that is created by breaking up a continuous tone image into a pattern of dots varying in size, shape, and spacing. Lighter parts of the image are made up of larger dots that overlap each other. Printed with one color of ink, the dots merge together or space apart to give the illusion of continuous tone.

• When enlarged, the dots from the halftone process become more visible. When black and white film is developed, the film consists of only two colors and can not create an infinite range of colors.

• Full color images are made possible by repeating the halftone process for each subtractive color. When printed, the semi- opaque property of ink produces halftone dots of different colors. This most commonly done using the CMYK color wheel.

• William Fox Talbot originally created the idea of halftone printing. As the inventor of Calotype Process, he was a major influence to the development of photography as an artistic medium. Talbot suggested using photographic screens or veils to produce the small dots for the halftone process.

• The first successful commercial press was patented by Frederic Ives. He had devised a way to break up images into dots, but without the use of a screen. His original development of the halftone process started with using a gelatin relief. He continued to improve on this idea, and in 1881 he made the first commercial production of the halftone printing plates. Later in 1885, Ives introduced an improved version of the halftone screen.

• Halftone screens are measured in a resolution of lines per inch (lpi). This is the number of dots in a parallel line of the screens angle. The higher the resolution of an image, the greater the detail that can be reproduced. The printing industry has standardized a set of known angles, which results in the dots forming small circles called

rosettes.

• Here is an example of the optical illusion that happens when multiple

colors are used in printing.

Work Cited

• "Halftones: A necessary Step in the Printing Process." Penn State Press. psupress.org, n.d. Web. 2 May 2011.

• <http://www.psupress.org/author/aaupguidelines/halftones.html>.

• Halftone. (2011, March 3). In Wikipedia, The Free Encyclopedia. Retrieved 17:03, May 4, 2011,

• http://en.wikipedia.org/w/index.php?title=Halftone&oldid=416856257