Ellipse Vrs Dot shape benefit "example attached"

[yorkie]

How much you wanna bet?

[blue moon]

For anybody wondering what happened . . . the thread went out on a tangent due to a simple misunderstanding. Dan cleaned it up to bring it back on track.

back to the topic . . .

I use the 40 micron 225 and it will hold some nice detail, but 3% at 55lpi or more, 'doubt it. I can hold the 3% dot from accurip (which turns out to be bigger than 3%) on the 330 smartmesh (at 62 lpi) with lower percentages opening quite a bit, but my understanding is that the 3% is the lower limit of that mesh. So 225 will probably max out at 5 (just my thinking). Going to 45lpi, should do the trick though.
What lpi do you use?

pierre

[blue moon]

How much you wanna bet?

so you think it is fabric moire?

[Dottonedan]

I use the 40 micron 225 and it will hold some nice detail, but 3% at 55lpi or more, 'doubt it. I can hold the 3% dot from accurip (which turns out to be bigger than 3%) on the 330 smartmesh (at 62 lpi) with lower percentages opening quite a bit, but my understanding is that the 3% is the lower limit of that mesh. So 225 will probably max out at 5 (just my thinking). Going to 45lpi, should do the trick though.
What lpi do you use?

pierre
[/quote]

What lpi do you use?

  To who's post are you addressing?  Is that Orion's or Yorkie's?

[Dottonedan]

How much you wanna bet?

I don't need to.  It's a none issue to me.

[blue moon]

What lpi do you use?

  To who's post are you addressing?  Is that Orion's or Yorkie's?

Orion's, but if His RH has some input, would love to hear it.

pierre

[yorkie]

My one question is if the 3% is really what the art called for or just Orion's guess? It looks a lot more than 3% to my eye.

If 3% is accurate, is Orion psychic? or involved? or what?

Anyhow, the big question is of the moire is visible in the screen or only shows its ugly self when printed on a shirt?

[blue moon]

My one question is if the 3% is really what the art called for or just Orion's guess? It looks a lot more than 3% to my eye.

If 3% is accurate, is Orion psychic? or involved? or what?

Anyhow, the big question is of the moire is visible in the screen or only shows its ugly self when printed on a shirt?

Yes, it looks like more than 3%. Most of this is all a guess without holding the actual shirt.

Maybe we can get some shirts sent to you for evaluation. I'd volunteer some shirts!

pierre

[squeezee]

I will add that we use 65 line art for our sim process. At more than 14 inches viewing distance it is hard to discern that there are dots much less a single or four angle set. I also believe at higher line counts mis-registration will be less noticeable.

I think that misregistration will be worse with higher lpi - imagine we have same angle screens and a slight misregistration.  The smaller (higher lpi) dots will be completely out of register with the other dots whilst the coarser dots will be partially covered.
btw Wasatch can produce any screen you want on the same film, just RIP before dropping onto the layout.  I'll have a look.  I can do the different screens in their process colour as well.

[Orion]

The line count is 65lpi. Went back and had the artist pull up the seps file. The white base in the area Yorkie pointed out is at 7% and the reflex blue is at 44%. I need to go back and find my little chart of dot size in microns at various lpi's. You guys are probably right, moire caused by the substrate. But do you know when I hold the shirt in front of me and look at it, the moire is barely visible.

[Dottonedan]

The line count is 65lpi. Went back and had the artist pull up the seps file. The white base in the area Yorkie pointed out is at 7% and the reflex blue is at 44%. I need to go back and find my little chart of dot size in microns at various lpi's. You guys are probably right, moire caused by the substrate. But do you know when I hold the shirt in front of me and look at it, the moire is barely visible.

You guys are probably right, moire caused by the substrate.

  We will never know now, unless you had kept the original exposed screens to see if it was a screen issue. if it wasn't a a screen issue, then you can look at garment weave interference.

The white base in the area Yorkie pointed out is at 7%

  If I remember correctly, you said the base was on a 230. You also mentioned using a 65lpi for that job. So if you used all the same line screen on all mesh as most would do, (holding a 7% dot, in a 65 line screen, on a 230 mesh... is hard to do) wouldn't you say?

Seems to be too high of a line count to hold those dots in that area (on a 230 mesh @ 65lpi). It's about the threshold (teetering on the brink of blockage). Any variance in perfection would send it over the edge of being blocked.  Having an DTS I-jet produced a more tighter dot (more accurate) than any of these basic digital film printers (to film) With that said, that means that your dot is probably smaller than most 7%'s from a 65lpi from these digital film printers. Thats going to make it even harder to hold than most are familiar with.

Knowing this info reinforces the idea that the area in question is mesh/halftone related. I'm not saying that it's it for sure, but it sure does make more sense. I will also add here, that 7% dot in a 65lpi is well within the area of something that would do what Yorkie said. Could be garment weave interference. It's within that threshold (as well).  I do not believe that mesh weave interference is a result of a 35% tint in a 55 lpi halftone though (as stated in his picture example in earlier post. I'm not knocking his statement. I'm not bashing him I just don't agree.

[Dottonedan]

I think that misregistration will be worse with higher lpi - imagine we have same angle screens and a slight misregistration.  The smaller (higher lpi) dots will be completely out of register with the other dots whilst the coarser dots will be partially covered.

I understand where you are coming from. I think what your really saying is that misregistration will be more visible where it it out with higher lpi. misregistration is misregistration but I guess it's semantic at that point. Going back to my original statement, It's my opinion that it would be equally visually "out" when using a single line screen versus a rosette pattern.

btw Wasatch can produce any screen you want on the same film, just RIP before dropping onto the layout.  I'll have a look.  I can do the different screens in their process colour as well.

This is VERY COOL.  That alone, make me want to get Wasatch. We used to be able to do this in Freehand in the beginning. Different dot shapes, different line screens. It was pretty cool and I made use of it back then.

[squeezee]

We used to be able to do this in Freehand in the beginning. Different dot shapes, different line screens. It was pretty cool and I made use of it back then.

I used to like Freehand, it did things that you wanted that Corel & Adobe don't.

[drdot]

The major issue with the selection of dot shape has to do with how the midtone (50%) area transitions. Most of this halftone business has it's roots in the math. I know, it freaks everyone out when you use the "M" word, but ultimately, all the things we deal with as screen printers can be reconciled with the math. In the case of dot shape, it is really pretty simple, so here goes.

The maximum dot area is at the 50% dot. This is the point at which the positive dot transitions to a negative dot. By this, we mean that on each side of the 50% tone, the dot area is identical, but one is positive and one is negative. So, a 40% positive dot has the same relative area as a negative 60% dot. 70/30, 80/20 and so on.

Now, the dot shape at the midtone join is very, very important for screen printers because our printing process puts down 6X -20X the amount of ink compared to litho or flexo, which are planographic printing processes (thin film ink deposit.) This is important because this thick layer of ink wants to squish around on the garment, especially if you don't flash.

As the dots connect to the adjacent dots, the geometry of the dot has everything to do with how much of a tonal dot gain increase you will experience at the join.  The absolute worst dot is the ROUND dot. As soon as the round dots touch at 50%, they form an acute angle (<90?) and this very narrow angle instantly fills in with ink, on all four sides simultaneously. It is not uncommon, under the very best conditions, to experience 40% dot gain in the midtones on textiles. This is not necessarily bad, because it can be mostly managed. Dot gain is a whole different discussion.

The SQUARE dot is better, but you still have all four corners joining at the same time and now the join is at 90?, so it is harder for the ink to fill in the wider angle, hence less dot gain with a square dot, but still very high.

Now we get to the ELLIPTICAL dot and life becomes much, much better. There are two excellent reasons for the improvement. The first has to do with the ASPECT RATIO of the dot. This means the ratio of the length (x axis) of the dot to the height (Y axis) of the dot.  Depending on the Postscript Spot function design, you can control this on an almost infinite basis. The purpose of the ASPECT ratio is two fold.

The first is to have the length of the dot connect in one axis before the other can connect. So, for instance,  we can have x axis connect at 40% and the y axis connect at 60%. You are decreasing the amount of dot gain caused by corner joins over a much larger tone range, and at two different tonal values.

Second, and critical, is that the angle formed when the x axis joins is an OBTUSE angle (more than 90?) and this is much, much less likely to fill in due to the ink squishing around. You are decreasing the amount of ink at the point of join so there is less volume to spread or squish together. The openness of this angle is determined by the aspect ratio. If you joined at 30% and 70%, the angle would be much, much more open.

So in this sense, the ideal would be an LINE screen with no dots. This was used for engravings many years ago before the halftone process actually became available. Today, while line screens can be used for special effect, they are not really all that popular.

I hope this sheds some light on the mechanics of how the ink behaves during halftone printing. The shape of the dot is influenced by the frequency (lpi) and the mesh thread as well. Generally coarser halftones >45 lpi and finer S Thread meshes, will allow for successful printing of square and round dots, but regardless, all halftones screen printed will benefit from elliptical dots.

Finally, elliptical, ellipse, diamond, euclidian elliptical, etc are all variation of elliptical dots. The generic family of ellipse is simply dots based on different aspect ratios.

[blue moon]

If you mean Coudray, well yeah he is.

speak of the devil . . . Great to see you here Mark!!!

pierre