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To answer your question: What is the mesh count of the screens they are using? An index print looks best when the artwork is separated at 200 pixels per inch (ppi) and printed with a mesh count of 305 for the screens. In the US, many screen printers have these high meshes available. They, however, usually use lower mesh counts such as a 230 mesh or even lower when printing spot colors on a daily basis. The setting in the RIP software (50 lines per inch) probably means your printer is using 230 screens and so some of the single dots may not hold. 55 or 60 lpi would be better... if they are using the higher mesh counts. All in all, it would still print though - just not with the detail that looks best for indexing. Here's some further reading: Semi-tones are also known as halftones. To determine the halftone frequency (lpi) divide the mesh count by 5 (source: www.photoscreenprint.com/tutorials/film-output/ ). Some, however, say 4.5 is enough (source: www.monstergraphics.net/separationresources/separationspecs.html ). Creating halftones is a different technique than indexing, often more appropriate for smoother gradients (one color blending into another color). Not that you can't index smooth gradients but doing so can be harder than the other methods available. For example, if using Illustrator, you would create a spot color gradient and let the RIP software (a special printer driver) create the tiny dots that are then printed on film. This, of course, means that the artwork is vectored. For raster images, the methods are CMYK or Simulated Process color channels in Photoshop, Simulated Process being the one that usually yields best results, but uses more colors/screens. In the end, deciding which method to learn and use doesn't come down to mastering one, but instead, mastering them all. Because in my experience, the method I use is determined by both the press and the artwork itself. You can see an example of someone creating simulated process half-tones in Photoshop here: th-cam.com/video/tEnaXjrSwc4/w-d-xo.html Hope this helps and good luck!