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Magnify Your Process to Multiply the Results

(December 2009) posted on Tue Nov 24, 2009

Using a loupe to check for errors makes for a good method of identifying flaws and making improvements in the printing process.

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By Thomas Trimingham

Edge-quality problems with films can indicate issues with several areas of film production. Additionally, it is important that the digital source is looked at to eliminate it as a root cause. Sometimes the problem starts from a low resolution scan or bad pattern in the values of the source file that is wrongly attributed to the RIP or the output device/printer. To avoid this, make certain that the original digital file used for comparison is a clean, high-resolution file that can be trusted to produce a quality image. This isolates one variable after first controlling other surrounding variables. Otherwise conclusions change in sync with variables. Areas in film production affecting halftone dot edge quality are primarily the RIP and the output device.

It is dangerous to assume that an RIP that produces dots from a grayscale value always does a great job. Some popular RIPs used for producing screen print films may even damage or degrade dots. The easiest way to check is to use the loupe and look at several different percentages of dots. Look for dots that appear misshapen, irregular, or infused with some kind of digital pattern. Sometimes an old RIP or software can interfere with the current one and produce strange or inconsistent results. If a film's dots appear to have multiple patterns across them instead of just the normal halftone quality, then there may be interference between software, and even hardware that runs the printing device. In this case, have an original, clean film that printed from the same RIP and printing process to compare with the damaged one.

Viewing the opacity of films initially doesn’t require a loupe because you can see if the darkest areas of the film positive are truly opaque by overlapping them with another film and seeing if you can see through the top one. The magnification process is helpful to make certain that the dots in a halftone pattern are completely opaque in nature, and they don’t start to break up in smaller dot sizes. This issue is more common on dry toner systems that may use a heat application to bond the toner to the film.


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