Newsprint halftone output for screen printing


I have been using GIMP for image processing to generate film positives for screen printing. I have been overall pretty happy with GIMP’s ability to deliver what I need. I did have some questions regarding the Newsprint distort filter. When making a halftone positive, the resolution/size of the dots are depending on the mesh count of the screen. The finer the mesh, the smaller the dot the emulsion will hold. The resolution is typically given in lines per inch (LPI). Most screen printers use photoshop/illustrator/corel draw/etc. and recommend a LPI that is the screen’s mesh count :heavy_division_sign: 5. So for my 210 mesh screens, I’d print halftones with a resolution of 42 LPI. I really don’t know how to achieve this in GIMP.

GIMP doesn’t have LPI for an output setting on the Newsprint filter; instead the user selects a Period between 0 and 200. I was wondering if there was any conversion between LPI and period? Yes, I can make several copies of an image with different newsprint period resolution to see which holds well, but this process takes up a lot of resources and time to test. Does anyone use GIMP for screen printing and have suggestions for making halftones? Is there a simple conversion I’m unaware of?

Thanks a bunch!

The Newsprint plugin I have has a LPI output setting. What version of Newsprint are you using?
Also you should look into the G’MIC plugin as it has a halftone feature in it. You may find that one more useful.

I am not using a separate newsprint plugin- but rather the Filters → Distorts → Newsprint in Gimp 2.10.34. Is there a separate Newsprint plugin? Am I missing something?

I haven’t tried the G’MIC plugin and will look into it.

The Newsprint filter in GIMP 2.8.x did have an LPI setting, but it was replaced by a GEGL based filter in 2.10 that does not have that, nor was it apparently intended to have that setting.

From the 2.10 manual: "Be aware that Newsprint is not a filter for generating half-tone screens for print, but for simulating the appearance of printing with them. "

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