[ShirlandDesign]

I'm trying to run a gradient from white to black across 12" of 230 mesh screen.

It's a 40 LPI elliptical dot screen (looking for a course feel to it) half tone run through AccuRip. I tried a 45 degree angle to the screen and had a horrible moire pattern to it. Tried 22.5 (AccuRips sugested) worse still.

I made a film of 9 rotations in 22.5 % increments from 0 to 180 and 157.5 looked like the most likely canidate, still no good.

I would hate to think I need to make screen tests for 10 LPI line counts to find one lousy combo for one stinkin design.

Any suggestions?

 

[tlbays]

Hi John

Make certain your film positive dots are sharp to start.
Your test film should vary dot line-count rather than angle.
Make one showing a range of line counts
(25, 35, 45, 55dpi, for example) all at 22.5 degrees.
The test should be run on the 230t and a 175-200t at some point.
Often, round dots are less prone to morie' and extend futher in highlights,
but eliptical ones make for smoother mid-tone transitions.

Happy trails!

 

[ShirlandDesign]

Greatly appreciate the advice Tom,
I'll run a couple of more test screens.

 

[Smokestack]

The screen mesh you will be using will 100 % of the time determing what your lpi should be. There is one basic formula that you need to know... Take the screen mesh tpi (threads per inch) and divide that number by 4.73 (that is the number that has always worked best for me... some use 5)

example... 230 (mesh) divided by 4.73 = 48.625 <----- that is what your lpi should be to avoid halftone pattern conflicting with the screen mesh on a 230. This is the formula to use for every screen mesh u want to use. There are other factors to consider when trying to eliminate moire patterns... loose mesh will sometimes cause moire... even sometimes the halftone pattern looks great on the screen but every now and then, the thread pattern in the garment itself combined with the halftone pattern can create a moire.. also... if you are using multiple screens... use the same screen angle for every color.. i always use 22.5 degree screen angle. Trust me.. follow those simple rules and u will never again be frazzled by the evil moire