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Error-diffusion screening

Conventional printing uses images whose tonality is created by variable-size dots (at fixed positions) called halftone dots. The uses a different method for creating tonality, with same-sized dots at randomized positions, called error diffusion.

Error-diffusion patterns are generated by the printer's internal circuitry. The benefit of error-diffusion printing is that the machine appears to generate 'continuous-tone' images while it is creating error-diffusion halftone images. If you look at a Designjet proof through a magnifier, you will see these error-diffusion patterns.

When properly calibrated, and when using an appropriate color management profile for the printer and type of media, an can match a print from a printing press or photographic process.

 

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The original image is free of tonal patterns -- it is called a continuous-tone image.

 

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The traditional halftone image (exaggerated here so you can see the dot patterns) shows clear evidence of the dots, their colors (cyan, magenta, yellow and black) at different printing angles.

 

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The error-diffusion technique creates dither patterns that create tonality in an image. These patterns are exaggerated here so they can be seen. Error-diffusion images print well, and look great when generated on an .


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