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 or piezio
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 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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