Gerber OMEGA CP, Reference Manual

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Chapter 18:
Choosing and Assigning Halftones
The choice of halftone that you assign can significantly change the appearance of the fill.
Unfortunately, choosing a halftone is not an exact science. This chapter presents guidelines and
procedures for choosing and assigning halftones.
What is a halftone?
A halftone is the dot pattern the printer lays down when printing process colors or spot colors
with a tint percentage. Halftones have two attributes
−
the dot pattern (usually referred to as
type ) and the size of the dots (usually referred to as lines per inch (LPI)).
To view samples of different halftone types and the effect of changing the LPI, OMEGA
provides a halftone sample chart for you to print on your thermal printer and review while
reading about choosing types and LPI. The sample chart prints on Scotchcal 220 using CMYK
process foils.
To print the halftone sample chart
1
Open GSPPlot to display the Open dialog box.
2
Open the following file:
C:\Jobs\Samples\Halftone.plt
3
Click Print to Device in the toolbar. The chart is printed.
When reviewing this chart, notice that the CMYK values are the same for each halftone sample,
yet because of the different halftone types and LPI’s used, the samples appear to be different
colors. This chart is a good example of how halftones can change the appearance of the fill.
Choosing the best halftone for the fill
Each halftone offers specific advantages. Choosing the best halftone is more of an art than a
science. In evaluating which halftone to choose, it may be helpful to start by answering some
questions. What is the purpose of the job? What size? What viewing distance? What colors?
What printer are you using?
As you gain more experience, you will discover the most useful type and LPI for your work.
Also, try pushing the LPI limits for special effects. In many cases, exaggerated large or small dot
sizes can yield dramatic new output from the same object or image.
Although OMEGA software will allow for a complete range of halftones, it is best to use larger
halftone dots (a lower LPI) for optimum printing with the GERBER MAXX. A Non-Optimized
Halftones Detected dialog box appears when a MAXX 2 job is sent to print if the chosen
halftones in the job are too small for optimal print quality.