Digital Prints

Commercial digital printing systems, imagesetters, and some binary, digital desktop printers
such as color and B&W lasers use digital halftoning as part or all of their image-rendering
methods.
Contone Imaging
Digital continuous-tone or contone imaging, most clearly seen in digital photoprinting
and dye sublimation devices, works differently. Image pixels are still involved, but instead
of using halftoning as a middleman to break the various tones in an image apart, contone
devices translate the pixel information directly through the printer to the paper. As
the image is being rendered, the printer is, in essence, asking each image pixel, “which
color and how much of it?” Therefore, the more pixels or the higher the bit depth, the
better the image. Because the printed image is made up of overlapping dyes of each primary
color with no spaces between them, the color transitions are very smooth and the
resulting images are very photorealistic (see Figure 2.14).
Alternative Screening (Dithering)
Certain branches of digital printing, specifically inkjet and electrophotography, now use
a relatively new screening type: frequency modulated (FM) screening or stochastic screening
to produce near- or at-continuous-tone images where the dots are smaller and more irregular
than halftone dots. Perfectly shaped, regularly spaced halftone dots are replaced with
more randomly shaped, irregularly placed ones. If you know what a commercial mezzotint
screen looks like, you’re not too far off (see Figure 2.15).
Chapter 2 ■ Understanding Digital Printing 55
Figure 2.14 Contone imaging, in this
case with a Durst Lambda digital laser
imager, produces photorealistic images
with overlapping dye colors.