Universal Laser Systems PLS4.75, User Manual

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Dithering
Dithering settings are used when printing graphics that contain grayscale or color bitmaps such as
photographs in all printing modes except 3D mode. A dither pattern is a special screen filter that is used to
convert a grayscale or color image to monochrome (black and white). The screen filter reduces the image
to black and white while preserving the illusion of shades of gray by varying the spacing of pixels (dots) in
the image. Darker areas have more dots spaced closer together and lighter areas have fewer dots
spaced farther apart. Since the laser system is not capable of directly reproducing color or shades of gray
this is the method used to mimic shades of gray in order to engrave or mark photographs onto material.
There are three choices for the dither pattern applied:
Halftone
The halftone dither pattern is a line-type filter which applies a 45° line screen to a color or
grayscale image to convert it to black and white. The line spacing of the line screen varies with
the density chosen so at lower densities the line screen is more coarse.
Image Density Lines Per Inch
6 and 7 180
5 90
4 60
3 45
2 36
Error Diffusion
The error diffusion dither pattern uses a random scatter filter to place pixels in order to represent
shades of gray, introducing a level of noise in the process. The pattern created will vary with
density chosen. Higher density settings, such as 5, will produce a more densely packed, finer
pattern and lower resolution settings, such as 2, will produce a loosely packed, coarser pattern.
Black and White Mode
The Black and White dither pattern is a thresholding pattern that thresholds at 50% black. Each
pixel in a grayscale image that is greater than 50% black will be converted into black and each
pixel that is less than 50% black will be converted into white. This dither pattern will not give good
results for reproducing photographs, but is very useful when printing images that should be black
and white yet may have some unintended grayscale pixels in them. A good example is a scanned
image of a text document that was scanned into a computer using a grayscale scanner setting.
Ideally the scanned image of text should be black text on a white background, but if a grayscale
scanner setting was used there may be very light gray pixels at the edges of the characters of
text. This dither pattern will remove those gray pixels.
Helpful Tip
Laser marking or engraving grayscale or color bitmaps onto materials requires a bit of trial and
error to achieve good results. Results will vary on different materials. As a rule of thumb, use an
Image Density setting of 5 using halftone or diffusion pattern on harder materials where you are
marking the surface. Use an Image Density setting of 3 using the halftone or diffusion pattern for
softer materials where you are engraving into the material.
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