Stochastic Printing vs. Conventional Printing

Stochastic Printing vs. Conventional Printing

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Stochastic Printing vs. Conventional Printing
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FM, AM, XM, Hybrid, Staccato, Segundo, stochastic, conventional, 200 lpi, 175 lpi, 20 micron, 10 micron, first order, second order; what is the difference between stochastic printing vs. conventional printing?

NOTE: Screening is the process after rasterizing PDF files in the RIP (raster image processor) during prepress. Halftone screening is done through software and creates very small dots, or cells, that are imaged onto a printing plate. The tiny dots create the illusion of continuous tone photographs when printed on press.

Stochastic Printing vs. Conventional Printing Halftone Dot Comparison

Top: 200 lpi conventional (AM) halftone screen magnified 200x.
Bottom: 20 micron (FM) stochastic screen magnified 200x.
Image: Gordon Pritchard

Advantages of Stochastic Printing vs Conventional Printing

  • Continuous tone photographic reproduction
  • Produces a larger CMYK color gamut on press
  • Renders greater detail
  • Eliminates moire patterns
  • Reduces ink consumption by as much as 10% – notice the ‘pooling’ of ink in conventional dot
  • Produces smoother gradients
  • More consistency in color throughout pressrun
  • Faster ink drying

Conventional screening (150 lpi, 175 lpi, 200 lpi) refers to AM screens, or amplitude modulation. This refers to halftone dots that are fixed on a grid, angled in 30 degree increments (except yellow: 15 degrees) and grow in size based on tonal value.

LPI = lines per inch

Stochastic screening (Staccato) refers to FM screens, or frequency modulation. This refers to micro-dots (20 micron, 10 micron) that are FIXED in size and tone values increase by adding more dots. The dots are rendered in a psuedo-random algorithm making them ideal for high definition details in photography and artwork. The micro-dots are rendered in a ‘weave’ to create very smooth tonal transitions.

Micron =1/1,000,000 of a meter

It’s important to note that stochastic printing produces a larger CMYK color gamut than AM screens. This occurs because light reflecting off the paper is filtered more efficiently, resulting in less ‘whiteness’ from the paper reflecting into the eye.

Also, reprints are less likely because of the stability in controlling color on press. FM screens are much less likely to be impacted by ink density variations on press. The ink film on press is much thinner and less likely to be affected. Notice in the enlargement photo above the ‘pooling’ of ink in the conventional halftone dots. This causes the press to use more ink than is necessary.

Have you ever seen printing with FM/stochastic screening? Please leave your comments below…

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    8 Comments

  1. I printed with Kodak Staccato 25 on uncoated (indeed) and coated paper in 2005-2007 and was really impressed by the quality v.s. normal AM. The advantages are less colour fluctuations during production, more detail in photos and much more detail in small graphics and small type (imagine a small logo and 6 pt. type) and faster drying. When printing on 8 up sheets in a sheetfed press where you often experience paper stretching towards the bottom left and right which results in misregistration, the colour shift is much smaller than when printing with AM. The downside that I can recall is: some issues when printing seamless pastel colours – artifacts that had something to do with the algorithm Kodak used but was supposed to have been fixed around 2010 or so and then the fact that images seemed to lack sharpening. I know a fellow who used a GMG solution to sharpen all images by default that are going to be printed with FM which seems to solve that issue more or less completely.

  2. Yes, when it was first attempted (late 80’s early 90’s I loved the continues tone look)and basically discontinued it because of the mid-tone situation and not being able to fix that – I went back to the basics. I liked the way the final product looked and hoped they could solve the problem – as I printed some poster in black and white with silver ink that were stunning, but again, it was the mid-tones where we lost it.

    Like I said, I loved the way it looked.

  3. Yes, when it was first attempted (late 80’s early 90’s I loved the continues tone look)a)d basically discontinued it because of the mid-tone situation and not being able to fix that – I went back to the basics. I liked the way the final product looked and hoped they could solve the problem – as I printed some poster in black and white with silver ink that were stunning, but again, it was the mid-tones where we lost it.

  4. I was slightly unhappy with the results because although the colours were correct, I would have liked a more generous use of ink, resulting in a more sumptuous result (for want of a better word). Instead, I found this printing good, but a bit ‘cold’.

    Has anyone felt something similar? It would be good to hear as another printer is recommending FM for a new job.

    • I forgot to mention that I am talking about printing on uncoated paper.

  5. What is the advantage of Stocahstic in a solid build area. Coverage about 85% of sheet

  6. Just a small clarification to your statement that FM screens produce a wider color gamut than AM screens because light reflecting off the paper is filtered more efficiently, resulting in less ‘whiteness’ from the paper reflecting into the eye.

    We see color in print because the ink filters the light that passes through it and reflects off the paper below the ink. With FM screens there is less unprinted area around the individual halftone dots for a given tone. Hence there is less light being reflected off of unprinted paper. It is that unfiltered light between the dots that contaminates the color that you see with an AM screen reducing its gamut. You can see that difference in ink/paper area in the graphic in your post.

    So, to put it more accurately – FM doesn’t produce a larger gamut. Instead, AM screens reduce your potential gamut on press. Theoretically, if you had continuous tone lithography where the paper is completely covered in ink you would achieve the maximum gamut that your inks are capable of.

    All halftone screening reduces gamut. It’s just that different screen patterns reduce it by different amounts.

    BTW, this is also one of the reasons that the near continuous inkjet printers have a larger gamut than an offset. press.

    • Correct. The resulting CMYK color gamut is ‘fuller’ than an AM screen in the area between the primary overprinting colors.

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