is this moire if so what to do?

[Inkworks]

Gilly, just for fun and to get the moire thing figured out a little more take two films with 1/2 tones, stack them on you light table and slowly rotate the top film to see the moire come and go between the dots, it's more fun than spirograph!  . In some cases you can actually see moire between the film and mesh in the screen, although that's easier on an uncoated screen. Almost any 1/2 tone can be angled on almost any mesh to be moire free, but sticking to peoples suggestions above will be the best thing as there are other factors to consider too.

[ScreenFoo]

I figured all the way to 0% would be fine because whatever we got is what we got.

But the pattern is all around the design at about that percentage.

The thing is that the thread is WAY smaller than the "blocked" area.  So something doesn't add up there.

I'm pretty sure I over exposed a bit... that is probably some of the problem.  We exposed at our normal Light Units which is ~25% EOM on white 156.   ()

I'd have all this dialed in but we are still struggling with coating consistently, so until then we just kind of wing it.

Unfortunately, if you're having issues coating, that's what will need to change before consistent halftones will happen.

Even if the dot is twice or three times the size of the thread, and part of it resolves, it can and will still create the types of patterns you're seeing there.  I mentioned a while back I thought of a thread and an opening as a smallish reasonable minimum dot size--on this mesh that would be about 170 microns--If my math isn't too addled, that's around 10% @ 55LPI.

I can only hope you're not trying to shoot 55LPI halftones on white 150 mesh.   

[3Deep]

I find that shooting halftones on white mesh is trouble from jump street try using color mesh like yellow or orange...halftones burn great on those colors I,m guessing cuz the light does not bounce around as it does on white mesh.

Darryl

[jsheridan]

I was asked in a PM if 22.5 isn't right, then what is?

Due to the wide variations of mesh out there.. the angle that works is the one that fits your mesh, not mine.

You have to test for it plain and simple.

[Frog]

160 (or 156) are not as easy to find in dyed mesh, but they are out there.

Remember too, that there are many different colors and shades (yellow, orange, magenta that I have seen) so a new exposure calculation should be done on each!

[Sbrem]

I was asked in a PM if 22.5 isn't right, then what is?

Due to the wide variations of mesh out there.. the angle that works is the one that fits your mesh, not mine.

You have to test for it plain and simple.

26° and 61° work well too, but you do have to test. Sometimes, only part of the image produces moire, which we've usually solved with finer mesh counts.

Steve

[ScreenFoo]

Murakami's own chart places 22.5 degrees smack dab in the middle of "OK" as far as a 55LPI halftone is concerned.  Although I'd be interested in a lesson as to why they're wrong, if they happen to be.

[Inkworks]

I think it has more to do with mesh count than angle in this case, throw that on a yellow 230 and he'd probably have no trouble.

[Gilligan]

For the record this was on 150-S thread.  It ONLY comes in YELLOW.

I mentioned white mesh as in the only thing that we actually tested exposure on.  We dialed in our exposure at about 25% EOM on white 156 mesh (static frame).  I no longer use those frames.

I'm just looking to get my coating in step and then I'll get all of these exposure times dialed in as well as run some halftone dot test.  I had printed out a sheet a long time ago with 25, 35 and 45 LPI... probably  time to do it again at 55 LPI with all the percentages.

[3Deep]

Dot Tone Dan had a test sheet on here that you could print out and burn with all types of halftones, check with him I,m sure he still might have it or I'll try and find mine.

Darryl

[Dottonedan]

Thaks Darryl,


Yes, here it is.  https://www.yousendit.com/download/UW13dFdhV3JRR2RqQThUQw


download soon. It's good for 5 days.


It's a ripless test. meaning, the dots have been made for everyone already. I am not a big fan of it since it's not THE best way to test. It is set to 1200ppi for crisp clean dots, but still, using the dot tone bitmap conversions in photoshop as apposed to your actual rip is not going to be a 100% true test but will be very good.  It may be the only test availabel so far for those who do not have a RIP.


I may have also included another set in grayscale for you to convert yourself using your own rip. I did this a few years ago and didn't open it again, so I'm not sure whats in it. You might find a cracker Jack toy.

Here is another good read from a post way back.


http://www.theshirtboard.com/index.php/topic,295.0.html

[Gilligan]

I took a grey scale image set and just kept moving it physically on my document and printing it out at different LPI's on the same sheet of film.

Passing it through the printer multiple times.

This let me get the 3 different sets on one sheet for exposure.

[jsheridan]

If anyone has freehand 10 hit me up and ill share my test films.

[Admiral]

I thought Murakami had a pdf about angles / LPI on different mesh counts.

Anyway we do 45LPI on 150S, if we need 50-55LPI we use 225S

The reason S thread can do higher LPI just fine is because of the much less thread in the way blocking the image/ink which means less moire.  We did 50LPI on accident once sim process, the 150S had a bit of a pattern but the 4-5 colors over top got rid of it luckily and it worked fine.

I was asked in a PM if 22.5 isn't right, then what is?

Due to the wide variations of mesh out there.. the angle that works is the one that fits your mesh, not mine.

You have to test for it plain and simple.

I thought the 22.5 degree angle was the angle to choose because it is best at not causing a pattern with the mesh assuming the mesh is perpendicular to the frame (which is the goal, and hopefully most mesh is).

[abchung]

I thought the 22.5 degree angle was the angle to choose because it is best at not causing a pattern with the mesh assuming the mesh is perpendicular to the frame (which is the goal, and hopefully most mesh is).

According to Mr Coudray at halftonemastery.com, 22.5 or 67.5 are the angles, because at 0, 90 degrees we get  interference from the thread. While at 45 deg we get interference from the knuckle of the two intersecting threads. So we must have an angle  that is far away as possible from 0,45 or90 degree..... Thus this is where he came up with 22.5 or 67.5 for single angle print....

Good luck
Anthony.

P.S: I invested in the halftonemastery.com course. I believe this will save me several years of heartaches in experimentation and guess work.