About Halftones and Gray Levels

A halftoned image is a series of dots arranged in a patterned grid of halftone cells, which yields the appearance of a complete image.

Screen frequency refers to the number of rows of halftone cells. The higher the screen frequency (in lines per inch) the sharper the halftone image appears (see 33 and 75 LPI examples in the figure).

Screen angle refers to the number of degrees from vertical at which the halftone grid is set. The halftone is set at an angle (usually 15, 45, or 75 degrees), to reduce moiré patterning. The idea behind halftone screens is to make the dots as fine as possible, so that the image itself is more visible that the dots. The observer will tend to focus on the 'big picture' while ignoring the microscopic halftone texture. When the dots are so fine that the eye can not resolve them, the image appears to be continuous.

TIP: If you have programmed and run a job, and received unexpected results, ensure that the system-wide settings are all set back to their defaults by clicking <Clear All> or <Reset> in the user interface. Then proceed to do job programming pertinent to your job.

Go to Choosing the Best Halftone Setting for information on the Production System Screen Frequency Demo Job.