Setting up files to screen CMYK...

[Brad Klausen]

Having never had a poster screen printed in CMYK...how does one set up the files...? I am guessing you just use the cmyk channels in photoshop and make those your film...but is it that easy...?

[Andymac]

let the printer do it to their specs

[caribou]

i thought it was pretty easy. there's probably a better way, but here's how i did it: if you've got the art already in CMYK mode in photoshop, go to the layers/channels/paths menu, and click on channels. the art is split up into the different CMYK layers. just click off all of the colors you don't want, and the layer you want should show up as an all black image (it'll change from the color you want to black). then just print them one at a time.

[S.Blake]

C 56
M 71
Y 86
K 26

55 dot

This works good for us on shirts! Ask RGT whats best for paper...

[RichieGoodtimes]

Those are weird angles.

I do 52 82 22 22. I guess my angles seem weird too, but mathematically it's 7° of 45°, which is what you need to eliminate tertiary moire.

I don't have a simple answer for screen printing cmyk on paper. Most of the decisions are based on what you are looking for as far as a final print.

Personally, I like to work at around 20lpi on paper. Those are big dots. I use straight 45° angles on a high mesh. I like to see the dots and from a distance they disappear. If I wanted to use smaller dots then I'd offset them by 7°. I wouldn't go any higher than 55lpi on paper, just like a shirt, because the line screen isn't dictated by the substrate, but the mesh you're printing with. If you're using 305s, I'd say 55. Lower than 305 but higher or equal to 160, I'd go 45lpi.

Process is not difficult to separate. It's seriously super easy. You don't have to do too much. If the art was created in RGB, which is how it should be created, for tonal Photoshop work, then it can be as simple as setting up a proper rgb to cmyk conversion and converting it to CMYK. I would use basic SWOP Coated 20 and modify it to 35% dot gain. The 20 in SWOP Coated 20 is the dot gain percentage. There is no such thing as SWOP Coated 35, so this is a custom conversion setting.

There's no need for all that layers shit. Either print the cmyk file as seps to a RIP or SPLIT THE CHANNELS and have 4 greyscale files, which you can manually halftone by changing to bitmap or RIP as you would the CMYK file.

[piemel]

remind me to slap richie during the melvins show

[Fools Gold]

Will setting my photoshop dot gain to 35% tell my RIP to fix the dots for said gain?

[squeegeethree]

We use angles of 22, 45, 66, and 90. Works for us. I think it helps to have a greater spread than Richies 7 degrees. Remember to check for a moire before coating your screen.

Tape the film down on a light table or white piece of paper. Put the screen on top and rotate it until you see the least but of moire (usually this is about 45 degrees to your mesh). Then mark where it goes on the screen in pencil and coat your screen.

There is always a moire but you can make it so small or large that no one sees it.

[RichieGoodtimes]

90? Seriously? For what, the yellow?

Personally I'd never sit dots directly on the mesh like that. Seems like you could potentially run the risk of losing an entire mesh line of dots.

7.5° off 45°, in theory, reduces the number of dots lost to the mesh more than most other angle sets. I forget where I read it but some dude had a full on equation about it. It's rounded down to 7° since most rips can't do half degrees.

[Jeph]

Those are weird angles.

I do 52 82 22 22. I guess my angles seem weird too, but mathematically it's 7° of 45°, which is what you need to eliminate tertiary moire.

I don't have a simple answer for screen printing cmyk on paper. Most of the decisions are based on what you are looking for as far as a final print.

Personally, I like to work at around 20lpi on paper. Those are big dots. I use straight 45° angles on a high mesh. I like to see the dots and from a distance they disappear. If I wanted to use smaller dots then I'd offset them by 7°. I wouldn't go any higher than 55lpi on paper, just like a shirt, because the line screen isn't dictated by the substrate, but the mesh you're printing with. If you're using 305s, I'd say 55. Lower than 305 but higher or equal to 160, I'd go 45lpi.

Process is not difficult to separate. It's seriously super easy. You don't have to do too much. If the art was created in RGB, which is how it should be created, for tonal Photoshop work, then it can be as simple as setting up a proper rgb to cmyk conversion and converting it to CMYK. I would use basic SWOP Coated 20 and modify it to 35% dot gain. The 20 in SWOP Coated 20 is the dot gain percentage. There is no such thing as SWOP Coated 35, so this is a custom conversion setting.

There's no need for all that layers shit. Either print the cmyk file as seps to a RIP or SPLIT THE CHANNELS and have 4 greyscale files, which you can manually halftone by changing to bitmap or RIP as you would the CMYK file.

I seriously just had an anyerusm reading this and trying to understand it.