Halftone questions

jeron said:

Hey guys i have a few questions about half tones.. this is my first attempt at printing halftones and i just found this image to try it out.

The first image is the actual print on the test square. the second image is the actual transparency i used to burn the screen. I used a 45 lpi halftone on a 220 mesh screen. I made everything in coreldraw with simple seps. The image contained 100% black, 45% black, and 15% black, before i sent it though simple seps.

as you can see the darker areas kind of merged together... i believe its called dot gain???? How would i need to proceed to get the dots better. In the darker parts of the stencil the blacker areas just washed completely out even though the transparency had holes going through. Is it just a matter of finding what percent half tone my screens will hold with my exposure unit??? I've read that anything less than a 15% and anything more that about 85% halftones and they will just washout... so i thought i would be good with how i had it.. but they washed out still..

Any tips would be awesome!!!

Thanks
Jeron..

Click to expand...

Jeron,

Great work here, I really admire you efforts to dial this in. My only recommendation would be to use a greyscale test sheet. I have attached a simple one with 10% increments in a zip file. It is DRAW 6 file. The bars start on the left with the original and go let with different levels of dot gain adjustments applied to them. You can use this a simple dot gain analysis to see what is going on your printing and which setting would produce the results. Once you have have things set for the results you are looking for the key is to keep you process consistent. That being your emulsion, screen exposure times etc.

The test sheet will give you something to measure and look at with a better ability to dial in your unique process analyzing the percentages of grey. 10, 20, 30, etc and looking at how the tints/densities shift or change.

This is just a simple test and you could much deeper to with more sophisticated tools.

If you want to do the test and shoot me an email I will be glad to go over it with you.

Tom,

thanks for the file. I was actually going to make one of those just to see what percent I can hold on the top and bottom...

So what your saying is if I need a 15% red but can't hold that I make it a 2 color job and use like a 30 or 40% pink or whatever gets me closest to the 15% red color I'm looking for... so in my case of the picture above like a dark grey at maybe 60% instead of trying to hold 80 or 90% black..

would coating the screen thicker or lighter have any affect on what I can hold percent wise?

Also what about the type of dot?

I think I noticed in the tease for ss4 that you can choose your dot type... that along with choosing your own registration marks makes me want the new version when it comes out...

Thanks,
Jeron

jeron said:

Tom,

thanks for the file. I was actually going to make one of those just to see what percent I can hold on the top and bottom...

So what your saying is if I need a 15% red but can't hold that I make it a 2 color job and use like a 30 or 40% pink or whatever gets me closest to the 15% red color I'm looking for... so in my case of the picture above like a dark grey at maybe 60% instead of trying to hold 80 or 90% black..

would coating the screen thicker or lighter have any affect on what I can hold percent wise?

Also what about the type of dot?

I think I noticed in the tease for ss4 that you can choose your dot type... that along with choosing your own registration marks makes me want the new version when it comes out...

Thanks,
Jeron

Click to expand...

SS4 is an entirely new animal there has been even more added since the sneak peaks. It has dot gain as presets and the ability to make a custom dot gain curve. The test print you have now is based on the presets and is basic to simplify the process. You could build out a test going in 1% increments or say 5% increments and test that way also. Or if you wanted to go in depth you could do that with some special equipment and readings and then convert those measurements into a custom dot gain setting or curve. A bit more complicated.

However the presets should get you very very close once you identify which one suites your printing process.

I always prefer simple round dot for screen printing even accurip, ryonet etc recommend round dot. Elliptical dots were developed for CMYK printing on paper. Fact is in screen printing those dots are not going to hold shape like paper printing because you are going to smash ink through a cheese grater like surface called mesh onto microscopic AstroTurf t shirt textile with pressure.

If you are having problems holding say anything below 15% you could then sep the 15% and lower in density and then mix an ink that 15% red and 85% white which would give you that tint. Then convert the 15% to the black point with the sample target balance. This would make the halftone from 15% to 1% much larger or printable while producing the same color tint as it would have been laying the down the 15% red on white.

You can take this even further but the math gets a bit complex. Lets say you did not want to print the 15% as solid color then you could convert the 15% black point to 80% with the sample target balance for somewhat smaller dots which you can still hold. So there you have made a 20% reduction in the halftone screen for that color which would then have to applied to the custom ink mix or 15% minus 20% or 3% would mean you would need to mix the ink and 12% red with 88% white to get that pink tint of the red.

Not to difficult and flexible based on what is the best approach for the way things work in your shop.

jeron said:

That sounds awesome Tom... do you have any idea when it will be ready to go? I know you've said it's getting close... do you have any idea on the price point for someone upgrading from ss3?

So is there a reason why someone would print a spot color of a mixed light pink ink vs just printing a 20% halftone red?

Also is that how you can recreate the tints of colors? Is it as simple as mixing 30% red with 70% white to get the same color as you would a 30% halftone red on a white shirt... or a 30% red tint in Corel draw?

Thanks,
Jeron

Click to expand...

Its always a give and take... I guess you might say.

Lets say you have a really light pink red tint under allot of black in which case you can lay down more ink/color for that tint with larger 80% type dots of the actual color as opposed to trying to simulate it with tiny red dots. This is where high-end sim process really comes into to play but is easier if you follow the math so to say.

The same could apply to printing that pink as a pink instead of trying to simulate it as tiny red dots.

Or going further if you cannot hold 12% dots very well then printing the pink at 80% dots is going to work much better for you. Especially in long print runs of several hundred or 1000s of t-shirts where the tiny halftones can tend to get blocked or clogged in the run.

The upgrade has a ton of new features...

Dot gain
Auto Trapping
Auto Choking
Interlocking halftones
Enhanced White
RIPing resolution options
Several New White Base Options
Interlocked WB to Black
Don't choke white white bases
Don't choke tints white bases

And more....

The upgrade will be around $100...

And Plugin itself of going to go up when it is released.

In the final testing stages now. Ufff

I love topics like this...



Well what where those? Round, elliptical, squares diamonds... I have come to believe that we screen printers are more like painters. We just use halftones to control the amount of ink/paint we smash into the woven t-shirt fabric. When you look at an image like this with color blends then you can actually see the ink start to mix while it was smashed into the fabric. Then it is going to be yanked, twisted and tweaked even more as you tear it of the platen and toss it into the dryer. Over time changed even more as it moves around in countless cycles in washers and dryers. Finally it will get its own distress look and settle into a favorite comfort t-shirt you wear to do chores around the house. In the end it becomes a rag in the garage wood shop.

Paper is a whole different game...


Over the last 2 years we have done some much R&D it is staggering. And we are by no means done yet.

Just for fun...