The Scoop on Stochastic Screening
Stochastic printing is not a new technology; In fact, it has been
around for more than 40 years. Of course it has changed since the early
days of 1965, when German printing expert Karl Scheuter began studying
the concept of using fine sporadic dots to reproduce images.
Publishers printing high quality, intricate photography can benefit
from stochastic screening due to its ability to reproduce images with
greater detail and smoothness, without much of an increase in printing
price. The challenge is that it is not widely available from printers.
And stochastic does not work well with low quality images, due to the
fact that the attention to detail that stochastic offers does not
affect images that are not strong to begin with.
"If you have a poor-quality image you’re better off using a lower
quality, conventional screening, which doesn’t highlight the image’s
errors in print," says Jeff McEnaney, director of prepress operations
and quality for IPC Print Services, a company that has been providing
stochastic print services for two years.
The modern version of stochastic printing is not quite as complicated
as it sounds. Instead of standard screening, which involves carefully
arranged rows of larger and smaller dots to create reproductions,
stochastic uses random placement of a large number of very small
uniform dots (10, 20 or 25 Micron) to create an image that looks more
uninterrupted to the eye. "In my opinion, the two most important things
to note when considering stochastic is the quality of paper you’re
using and the quality of the images in your magazine," McEnaney says.
‘The real benefit of stochastic is getting rid of moire.’
However, paper quality affects the quality of the image when dealing
with stochastic, which can jack up printing costs. Most printers
recommend #3 coated sheets or better for consistent, flat images for
smoother results. "The better papers have a better gloss to them," says
McEnaney. "The surface affects the way the print goes down on the page."
Perhaps the most notable benefit of stochastic is moire reduction.
Moire does not exist when there are no screen angles, leading to a
noticeable color benefit, especially in lighter flesh tones and
pastels. But there are some downfalls to the method, including piling,
an effect of printing that puts too much ink on the paper, which can
pull the coating off of the paper.
According to McEnaney, many pre-press manufacturers have the ability to
do stochastic, but shy away from it due to the piling risks. "The ink
and water balance have to be right," he says. "There are a lot of
technical details. The most important thing is your printer needs to
have good color management in place and good process control in the
prepress and press room environment."
Lack of Demand
It appears as if the larger printing houses are offering stochastic, as
well as some independent smaller providers, but although it has been
around for a while, publishers and advertisers do not seem to be
demanding it as the end-all of magazine printing preferences.
For the most part, printers are still testing the waters when it comes
to stochastic. "We have the capability of doing it but we haven’t seen
a very vigorous demand for it," says vice president of sales for Fry
Communications, Steve Grande. "We have the software and plating
equipment. It makes sense for certain type products and for others it
Stochastic is also being used for proofing, as a method that allows
publishers to view pages that are able to accurately predict what the
image will look like. "Various methods of ink laydown, in any printing
process, will define specific and possibly different color results"
says Bruce Sipiora of DuPont Imaging Technologies.
"Conventional and stochastic printing use different approaches to ink
laydown," he adds. "With modern proofing methods and color management,
and in particular, color managed ink jet proofing, we now have the
ability to characterize the color results of these different printing
methods. We can make proofs that are highly print predictive."
Grande says there are no significant cost increases for stochastic over
conventional printing styles. Although it has not truly caught on at
Fry yet, stochastic options have been creating a bit of a buzz
recently, related to the rising costs of oil. "Some people are
believing that stochastic printing combined with strong grey component
replacement technology may provide some ink efficiencies, whether or
not that all pans out remains to be seen," he says.