7-4 Advanced Imaging
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Keep in mind that the higher the lines per inch, the tighter the screen
on the image will be. To produce higher levels of gray without using
a lower line screen, you must print at a higher dpi. An illustration of
this would be to print the same image at the Accel-a-Writer 812’s
1200 x 1200 dpi with the same 75 line screen. You would now have
approximately 256 levels of gray (1200/75=16; 16 x 16 + 1 = 257).
Use the following table as a guide when working with levels of gray.
LPI To Achieve 256 Levels of Gray
Printer
Resolution
LPI
1200 x 1200 dpi
75
600 x 600 dpi
38
Line Screens
Knowing how many levels of gray you would like to achieve is one
factor in determining the appropriate line screen to use. Depending
on the individual image quality, some degree of experimentation
usually is necessary to produce the best possible output. You do not
always have to achieve 256 levels of gray for the best output. We
have found the following line screens (lpi) to work the best: 60 for
600 dpi and 95 for 1200 dpi. Trying these line screens generally
gives you a more precise idea of the optimum output for a particular
image.
Note:
Your Accel-a-Writer 812 features XANTÉ’s new enhanced
screening technology which lets you select different gray
level and gamma correction combinations to further fine tune
the quality of your output. See “Gamma Corrections” and
“Enhanced Screening” later in this chapter for more details.
