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Introduction
What is a Halftone?
It is easy to expose solid spot color images onto screens using inkjet output. But, the minute you have
shading or gradations (commonly called Grayscale Images), there is no way to expose that on a screen.
The grayscale image must be converted into small dots called halftones. These solid images can be
exposed on a screen. This is how all traditional offset and screen printing is done when printing grayscale
images. Closeup a halftone looks like a series of random dots. From a distance the eye blends them
together just like a TV screen and the image appears to have what is called a continuous tone.
With a rip like T-RIP you can dictate the size of the halftone dot. Most general screen printing on T-Shirts
uses a frequency of halftones per inch of 55 (called LPI or “lines-per-inch”). And, you can dictate the
angle of a halftone dot. When exposing halftone dots on screen mesh you can get patterns called moirés
and being able to control the angle of the halftone pattern can eliminate moiré problems when burning
screens.
Newcomers to this type of printing often zoom in on an image and think they are seeing halftones when in
fact they are simply seeing the small pixels that make up the image. The following photo shows an
original grayscale image, a zoomed in view of the image, and the zoomed in area converted to halftone
dots.
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