Ink on Paper

It is important to have a basic understanding of the ink-jet process. Don't worry, we won't speak of picoliters an piezio heads!

Ink on paper acts like a filter. Light passes through the ink, hits the paper and passes back through the ink. Black ink absorbs all the light bouncing back through it. Magenta ink absorbs the green light passing through it, and so on. This is interesting (to some of you!), but why is it important to understand how ink on paper works? The importance lies in understanding that the color of the paper you use will affect the color in the image. If you use a very cream or natural color paper, some of the blue light has already been absorbed by the paper before it passes back through the paper. This does not mean you always need to use an extremely bright white media, but you need to understand the limitations paper color will impose on your color range.

Halftone vs. Stochastic Screen

It is also important to understand that the thousands of colors reproduced in a high quality ink-jet print are produced using only 7 to 12 colors of ink. This is accomplished through a "screening process" where by the ink colors are applied in varying amounts to combine and fool the human vision system into seeing many colors. There are two basic screen system; halftone and stochastic.

Halftone Screens

Halftone screens are used when printing images on a printing press. The lines of the "screen" represent the image resolution when it is printed. A grayscale image is produced by varying the size of the halftone dots which occur at the intersection of the X and Y axis screen lines. This is also known as amplitude modulation or AM screening. This creates the illusion of a "continuous tone" image using only black ink. Most images printed in newspapers, books, magazines and other printed materials are reproduced using this technique.

 

       
Example of halftone screening. Photo by Carol Garutti

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