I'm getting ready to try my hand at an image with a gradient - just one color. My basic understanding is print @ 22.5 and 45lpi. I also understand that I'll experience "dot" gain of 30-40% when I print but what shape should the dot be? My RIP software gives me these options - is there a standard or does it "depend" :
Round
Diamond
Line
Elipse
User Defined
An additional question is, is there a formula for determining mesh size for the printing. This image will be 8"x4" - black plastisol on white T - for testing purposes I was going to burn it on a 230 screen but at this point it's just a guessing game for mesh size - I don't like guessing
The image will be similar to this but I still need to lighten gradient to account for dot gain. Thanks in advance!
Divide your mesh count by 3.5 to get lines per inch. I think elipse for dot shape.
Is this the minimal mesh count? So with this math a 156 would work if my frequency was 45? but if I wanted to use the 230 then it should be 65? Do you have any links to info that would clarify the "why" behind it or if you have time and the inclination would you mind clarifying. I'm the kind of person that likes to understand processes.
Here is the link where I got the info. I saved it in my favorites for reference. I believe he mentions the why sort of but is based on four color printing. I am looking for another link I thought I had saved.
Calibration is the single biggest problem with halftone printing. This is a result of the mesh, film, exposure, ink and printing technique.
Moire is the second biggest problem in halftone printing. Moire resulting from mesh, halftone and textile are the problem.
The spot function defines the shape of the halftone dot. Round, elliptical, diamond, euclidean all are based on using a dot inside a cell. Given everything else remaining equal, all of these dot shaped spots will function similarly. User defined allows a math function to be plugged in to a different shape spot. For example, one time i wrote a spot function that was a hybrid of a diamond and a dot, which resulted in pointed leading edge and a round trailing edge.
The "line" spot function is unique. Rather than forming a spot, the function forms a line. This allows the line to be wider and continuous. There is only 1 angle involved with a line, where where dots have 2 angles separated by 90 degrees.
Right now i'm working though the moire issue. What i'm finding is that it is combination specific. Where a 45 LPI screen at 45 degrees on a 305 mesh WILL produce a moire, a higher LPI screen at the same 45 WON'T but shifting to a different mesh count will change the results.
If you are printing the shirts yourself, the file looks like a great test file. Burn some screens and have some fun!
fred
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ImageIt: Thanks for the reply. I'm burning some screens this weekend to begin trying to find a working solution for the image I want to do.
A friend of mine is a graphic artist and is always emailing me examples of work he's doing and pestering me to figure out how to print some of his simpler "fun" pieces.
I've been trying to gather as much info as possible so I feel like I'm tackling halftones from a somewhat informed position - looks like I'll be doing a LOT of test printing
Halftone "dot" shape - which works best? 
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