screen printing > 4 Color and Simulated Process Printing

halftone measurment results. WOW, dot gain galore!

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yorkie:
To gain control of calibration, the first decision to be made is to decide if the rip based calibration should be duplicated into a second print queue or if the rip calibration should act as a baseline, where the baseline is modified within a graphic application. I've done it both ways, and a combination of the two. There is no "right way"

With rip based calibration, multiple queues are defined. One "print queue" would print exact as you print today. The second print queue would define a different set of calibration parameters. The print queues are named to be meaningful, such as you might have a queue for high opacity white, a second for underbase white, a third for a semi opaque inf family and a forth for process inks. The person outputting would need to send the correct separation to the correct queue and the predefined calibration will happen.

In application based calibration, you would have similar calibration curves to define  high opacity white, a second for underbase white, a third for a semi opaque inf family and a forth for process inks. In the case of photoshop, the curves would be defined as the curve shown above. For illustrator, a .ppd file can be defined with similar curves. The biggest problem with application based curves, each application does calibration in a different way, so once you calibrate photoshop, you need to calibrate illustrator, then corel, then quickseps or some other sep program.

One way to conceptualize calibration is as a graphic equalizer for an audio system. Rip based calibration is like the head unit, where application calibration is the things which plug into the head unit. For rock music, the calibration can be pushed to "11".  A 50% screen might be best printed at 50% or maybe 67% looks better. With calibration control, you can choose your choice. For screen printing, does anyone SERIOUSLY want a 5% screen printed on a shirt?? or should the 5% print as a 15% or more?

blue moon:

--- Quote from: yorkie on May 05, 2011, 11:56:18 PM --- For screen printing, does anyone SERIOUSLY want a 5% screen printed on a shirt?? or should the 5% print as a 15% or more?


--- End quote ---

and therein lies the rub! Anybody here tried to do this? What were the results?

pierre

yorkie:
Back when i was doing my testing, i couldn't print a 5%, not even with process color inks. The bottom 15% of the halftone was negatively impacted by screen and textile moire interference. Because the dot size of a 5% halftone is so small, it can hide in the intersection of the mesh or the gaps between the knit of the shirt.

The next time i get motivated to work on rips again, i'd like to modify the halftone engine to keep the dot size no smaller than some fixed value, then for halftones that need dots smaller than that size, the halftone engine would begin to removed dots in a preset pattern.

If you want to know if your getting all of the tonal range, you'd need to turn calibration off and print a graduated screen, like the one attached and then print it again with calibration on. With calibration on, you can see what is happening in the low range of halftone, then compare where the low lend of the calibrated halftone matches the uncalibrated output. This will show if the calibration curve is clipping any of the usable halftone range.

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