Showing posts with label Stochastic. Show all posts
Showing posts with label Stochastic. Show all posts

Monday, February 16, 2009

AM versus FM Screening

After having a recent in-depth discussion on screening, I thought that I’d share the two types of Acme’s screening capabilities:

AM Screening

-Definition: AM screening, or Amplitude Modulation screening, is the conventional screening seen most often in commercial offset printing. In AM screening, the dot pattern is a repeating floret pattern. Tone-density change is seen by amplifying or reducing the size of the dot. Standard AM screening at Acme is 175 LPI (or lines per inch).

-Some of the major benefits are:
1.) Easiest screening type to make color moves on press.
2.) Smoother tones than FM screening.

-Some of the major disadvantages are:
1.) Unwanted patterns and effects (e.g. moiré patterns) are more likely.
2.) Difficulty truly representing very low densities (it will look flat).

-Some of the uses:
1.) Projects that require control of color on press (i.e. typically any product-focused or corporate-focused projects)

FM Screening

-Definition: FM screening, or Frequency Modulation screening, is also referred to as stochastic screening. This screening utilizes one very small dot size (20 microns), in a randomized pattern, with frequency of the dot to create tone-density change (i.e.: the less number of dots, the lighter the density). At Acme, we utilize staccato screening, which uses two a 20 micron dot in the low and high densities and a 25 micron dot in the mid densities, thus allowing for a much smoother mid density range.

-Some of the major benefits are:
1.) Able to capture much greater details.
2.) Very vibrant color.
3.) Reduced moiré dot patterns.
4.) Dot patterning is more similar to Epson proofs than AM Screening (though, the dot shape differs)

-Some of the major disadvantages are:
1.) Get ready…this is THE biggest reason why you might not want to consider FM screening: it is very difficult to make color moves on press.
2.) Clustering due to randomization of dots.

-Some of the uses:
1.) Projects requiring vibrant colors (e.g. outdoor photography, etc.)
2.) Projects with very fine detail.
3.) Projects with objects that have a tendency to moiré.
4.) Projects with objects that have very low densities (e.g. glass/crystal-ware, etc.)

Every project has different requirements, so it’s best to have your favorite print rep (me....if I’m not your favorite, I’ll still help you out!), consult with you prior, to understand the benefits and disadvantages that it will have on your project!

Friday, May 25, 2007

What the heck is stochastic printing other than a pretty picture?!

Whew...nothing like getting nitty-and-gritty on a Friday evening. I had someone mention stochastic and staccato printing today. So I thought I'd share the story.

The Definition
There are two primary rules to stochastic printing:
1.) The pattern of dots is randomized, and
2.) The dot is significantly smaller than the standard line-printed dot. Density is determined by a frequency of dots in stochastic printing.

Basically in regular (or AM) line screen printing, the size of the dot shrinks or grows to basically portray a change in percentage or lightness/darkness of an image. In stochastic (or FM) line screen, the size of the dot doesn’t change, but rather the frequency changes.

If you’ve heard the term staccato thrown around, this is basically an upgraded version of stochastic. The primary difference is that the size of the dot in the mid-tone range (40 – 60%) increases ever so slightly (FM 25 as opposed to FM 20…the 20 and 25 being a micron measurement). After much testing, it was discovered that the smaller dot made the image a little grainier than the rest of the tone percentages. This was a simple change that seemed to smooth the entire image out.

The Benefits
AM screening, or stochastic/staccato printing, is a great way to re-produce high-end, detailed photography. Additionally, it is a great way to give high-end jewelry (especially glass and clear gems) more life and curvature. Stochastic/staccato is also seen in: nature and human photography (staccato especially performs well with flesh tones), and detailed still life photography.

The Negatives
Many printers establish an upfront service fee for stochastic/staccato printing. On the other hand, many estimators estimate the increase of make ready time/material it will take after each plate change. Regardless however, there is some cost to this service. So as I recommend to all my customers, stochastic/staccato printing should be something that is planned appropriately prior to go to press.

That's it! Okay...more fun stuff after this post...I promise