Image Resolution
Conventional Screening AM and Satin Screening (Stochastic) FM
AM Screening, or conventional screening:
Dots are printed using a standard line screen. 133, 150, 175, and 200 are pretty much the standard.
The number indicates the number of dots required per inch to print the image. Resolution is the number of pixels in your file required to generate this line screen. Each colour of CMYK has it's own angle that it will be printed at. If you examine a printed piece under a magnifying glass you will see a rosette shape to the dots. The screen angle varies 15degrees for each colour. This reduces the chance of dots printing on top of one another.
AM Screening is basically equal spaced dots, with variable size dots. This is how printing has been done up until the turn of the century.
Satin Screening (Stochastic) FM Screening.
Very similar to AM screening in that dots are still used in the printing process. The real difference is in how these dots are configured. The dots are all the same size, however the frequency and spacing between the dots varies. When the dots get close enough they create a worm like shape that can be seen under a glass. These dots are all equal to a 1% dot at approx 175line screen. So, needless to say you need a printing press maintained in great shape to be able to reproduce this technology accurately.
What do you gain? Well, with a much smaller overall dot size, your image detail is quite sharp. Highlight, and shadow detail is improved dramatically. More so in the shadows. Solid colours also now have a spot colour appearance as you do not see any dots in blends or in solids. To that naked eye any ways. It truly is an impressive printing technique.
Can it be used on every job, and are there any drawbacks?
Depending on the stock, yes it can be used. Since Stochastic uses very small dots, it needs to be printed on a stable substrate. Through our experience cover stocks, and weights of 100lb coated or greater work really well. Other than detail are there other benefits. Drying time is drastically reduced. This is a huge benefit when jobs are in a rush and need to be backed up right away. With the smaller dot sizes, the air allows them to cure almost immediately. Colour on press stays much more consistent. The down side is, if you aren't happy with the colour, it is very difficult to make colour adjustments on press. AM screening has a much greater variable to alter colour. Depending on the files supplied, each process has it's benefits.
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• Rule of thumb is multiply your line screen by 2 and you have your line screen for your photos. (ie. 150 line screen is 300 dpi and 133 line screen is 266 dpi). Line are files can be 600 dpi. Remember to place your photos and illustrator files in at between 80% and 115% to avoid resolution problems. Over ressed files will look just as bad as under ressed files. |
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