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Stochastic printing process ability to produce a larger CMYK color gamut is one of the best secrets to producing high quality color on press.
Conventional halftones, often referred to as AM screens (amplitude modulated), distribute ink over a grid of dots that increase in size for darker tones. Throughout the tone scale, the frequency of dots remains the same, but the size or amplitude increases. The ink and water requirements vary greatly throughout the tonal range, causing a basic lithographic instability for which there are no on press controls.
An alternative to traditional halftone printing is stochastic printing process. The ink water requirements are more evenly distributed throughout the tonal range thereby overcoming the inherent instability of the AM screen. Stochastic printing is referred to as FM screening (frequency modulated) because of the number and frequency of dots changes with tonality. Note that the average size of dot structures, in stochastic printing, remains relatively constant through the tone scale. The dots are positioned in a pseudo-random pattern to avoid moiré and patterning problems.
Many people are aware that stochastic printing (FM) brings certain quality benefits to print, but few have realized the true potential of stochastic printing to deliver more predictable and stable color to their presswork and a larger CMYK color gamut.
Let’s look at the comparison of primary overprint colors (Red, Green, Blue) and how the screens compare in trapping/overprinting subtractive colors (Cyan, Magenta, Yellow) between stochastic printing and conventional halftone dots.
Stochastic Printing vs Conventional Printing Halftone Dots
Primary Red – Stochastic Printing versus Conventional Halftone Dots
Primary Green – Stochastic Printing versus Conventional Halftone Dots
Primary Blue – Stochastic Printing versus Conventional Halftone Dots
NOTE: the ink sequence on a printing press is black, cyan, magenta and yellow. Each ink gradually decreases in tack for overprinting efficiency to allow primary colors – red, green, blue – to be as bright as possible.
Notice the greater range of tones in all three primary overprint colors with stochastic printing (FM) resulting in a larger CMYK color gamut.
This demonstration shows that stochastic printing (FM) prints cleaner, with greater vibrancy and a midtone color gamut that is not achievable with AM screens.
In the example above, you can see the effect in a number of areas. If you look in the magenta patches you will see a distinct difference between the conventional halftone dots (AM) and stochastic printing (FM).
The tiny dots that make up a stochastic printing (FM) are actually more efficient at trapping and remitting light than conventional halftone dots (AM) screens. A small amount of light on the edge of every dot gets scattered through the paper and through the ink. This is what is called optical gain.
With stochastic printing process, a larger percentage of light that hits the printed sheet passes through the ink. This means that less ink is required for a given visual tone and the increased optical effect filters out a greater percentage of the complementary colors that are reflected from the paper surface. It is the complementary colors that contaminate the color we should be seeing and there is less of it getting through with stochastic printing.
True High Definition Color.
Which color would you prefer? Please leave your comments below…