Halftone Printing

When we view an image on a monitor or on a television screen, we see the image in pixels. However, we use digital halftone to print the same image on a printing press. Explain why we need two different approaches for reproducing the same digital image.

There are two different approaches to produce the same digital when you consider viewing an electronic sample on a monitor or television screen verses a printed sample on a printing press. With the monitor, removing or adding light changes value. The major issue with printing lies with the limitations of the ink. Consider painting for a minute. Painting is similar to ink as it uses pigments for a subtractive color system. If you needed a lighter shade of black you would add white paint to black to change the shade. In printing there is not ink “white ink” to add to black or any color for that matter to change the value. To print a photograph for example you need shades of gray. With printing, the ink is on or off. This creates a big issue when trying to reproduce gradients, and any other value other than solid black or the absence of ink “white”. To achieve this type of effect printers use a halftone system where an image is converted into a “pattern of very small dots of varying sizes with equals spacing between the dot centers” (Romano, 212). The dots vary in size and therefore create an optical illusion of different values to create the needed shades.

Work Cited:
Frank J, Romano. Pocket Guide to Digital Prepress. Clifton Park, NY: Delmar, Cengage Learning, 1996.

Resources
AIO Lecture Week 2
Pocket Guide to Digital Prepress.