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Discussion Starter #1
I realize this is a bizarre question, but i've been thinking about this idea for some time...

Let's say i have a very large raster image, to be printed perhaps at 24x36", from a digital solvent printer onto vinyl.

i wonder if there's any way that i can set it up so that it looks like it had been printed with four color process, at a 20 or so halftone frequency.

the idea is to have a blown-out halftone looking image where you can easily see the cyan, magenta, yellow and black comprising the image with an elliptical dot pattern.

if this could be done in illustrator and be vectored somehow that would just blow me away.

any suggestions??

derek
 

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Discussion Starter #4
Ann,

thank you so much. i was actually trying to print separations and then scan them back in to trace in illustrator.

tried your suggestion with a trial file and it worked great. the only thing is i need to figure out the opacities and everything to get it to look right.

derek
 

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Discussion Starter #6
Both Illustrator and Photoshop have a filter under pixelate called color halftone. this will make any color image look like a color halftone. The variables allow the selection of coarseness. fred
Thanks Fred, I had a feeling you might chime in... you often do when it comes to the world of CMYK...

the color halftone filter is something i've never understood how to control, but perhaps that's because i've never printed any results... they always look so mangled on screen; much like converting to bitmap in photoshop, or bringing a dcsII file into illustrator. i just never put my faith into what looks like such a limiting filter.

i was able to bring each color channel into illustrator as it's own bitmap, trace under the detailed illustration preset, and assign each "channel" its appropriate color and register to achieve mediocre results.

the problem is that i'm not sure how detailed of a trace i can get with halftone dots. my first trial was at 20 lpi.

tomorrow i'll try 40.

the idea is to get the dot pattern visible in the print, and also have the image visible, and on top of that be scalable. I plan on using this element in large scale to wrap my vehicle.

thank you guys all for your help. i will post my results as they come, and of course, any more reccommendations are warmly welcomed.

derek
 

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Discussion Starter #8
Im not sure if this would help, but have you tried giving every channel different lpis?

haven't tried it yet, but the look of the image is definitely effected by the layering of the different "channels" in Illustrator. i've found on first trial that, from bottom to top layer, it looks best as y, m, c, then k.

i notice that adobe's "default angles" run between 52 and 60ish on lpi with to-the-tenth angle settings for what i assume to be a well-calculated mathematical answer to solving the moire pattern, but i have yet to apply this idea to a much lower, AI traceable lpi. so far i've used 20 lpi, with varying screen angles in testing.

I assume that someone with advanced mathematical knowledge, or another with a whole lot of trial and error time on his/her hands could find the "magic numbers" to meet this challenge, but unfortunately without the knowledge, time or patience, i am forced to find a quick solution.

hopefully a few controlled experiments with lpi, opacity and color percentages tomorrow will yield satisfactory results.

derek
 

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Hope it works out for you, I don't know enough about process to really help out, but I have been told that when you are doing fine detailed process each channel gets a different angle. I also tried searching on google for some photoshop tutorials on comic book halftone effects. There were a couple that might be of use, but nothing exactly what you are looking for. Good luck!
 

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I don't know enough about process to really help out, but I have been told that when you are doing fine detailed process each channel gets a different angle.
Actually, I've heard the opposite. I participated in a class at the Long Beach ISS Show, and was shown 2 samples of process prints on darks. One had all the same angle, the other had different angles. There was no difference in the samples.

Traditionally, when I print halftones, I try to make it for a 156 mesh. So the SMALLEST dot I use is a 35lpi, MAYBE 45, but that would be pushing it. I always use a 61 degree angle, as this is one of the most optimum angles to set dots along the right angles of the mesh without them falling through. Think about it...when you look at a screen, what angle are the lines?
 

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Actually, I've heard the opposite. I participated in a class at the Long Beach ISS Show, and was shown 2 samples of process prints on darks. One had all the same angle, the other had different angles. There was no difference in the samples.

Traditionally, when I print halftones, I try to make it for a 156 mesh. So the SMALLEST dot I use is a 35lpi, MAYBE 45, but that would be pushing it. I always use a 61 degree angle, as this is one of the most optimum angles to set dots along the right angles of the mesh without them falling through. Think about it...when you look at a screen, what angle are the lines?
Sounds great. I won't disagree with you because I really don't know anything about process printing, just hearsay. I was under the impression that you used different angles though so you don't get Moire.

U.S. Screen Print & Inkjet Technology | QUICK GLOSSARY

Angle
The angle of the dot is the angle at which the dots chain together. The problem with most computer graphics programs is that the angles of the halftones are generally great for offset printing but not good for screening. A lot of computer programs use 45 degrees as the default angle. Actually, 20 to 25 degrees is good for basic halftone work. If you are doing a process color job you can try Cyan 15, Magenta 45, Yellow and Black 75, or Cyan 22.5, Magenta 52.5, Yellow and Black 82.5.
 
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