Example of halftone readings from an non linearized RIP

[blue moon]

'just took a reading from a non linearized (un-calibrated) RIP. These are pretty much par for the course as I see them several times per year and they pretty much all have very similar numbers. Note that the 1% dot actually comes out as a 5%. This just goes to show that when somebody says they are holding a 1% dot they really are not. They are holding a 5% dot in case like this. Physical limitation of the 305 standard mesh is calibrated 3% (from what I've been told and what our experience backs up).

1 5%
2 7%
3 9%
5 13%
7 16%
9 19%

10 20%
20 35%
30 50%
40 63%
50 72%
60 84%
70 93%
80 98%
90 100%

Go print the test file on top of this section and if your halftones are closing in before 99% your RIP is off. . .

pierre

[tonypep]

Agreed

[jvanick]

Looks about right from my experience here too.

[Sbrem]

Good observation there, Pierre.

Steve

[jsheridan]

For those using Accurip..

the ability to adjust your tonal curve was removed in the last update.. when asked, they said you don't need it.

this just proves how wrong they are.

[ABuffington]

There is also the dot gain that occurs during print which is just about the same.  One of the other issues with inkjet imagery below 10% is that older heads can scatter the pico liter dots which are quite transparent and prevent imaging on the screen.  True Film with a solid circle/ellipse halftone below 10% is far easier to image, up until the dot size is less than mesh thread diameter.  At that point halftones get blocked out anyway.  I have a client trying to image 180lpi halftones.  This is mathematically impossible in lower percentages.  Even pushing 133 has severe limitations on lower percentage values.

180 lpi is 1/180lpi = .0055 inches for a 100% dot.
.0055= 139 microns so a 5% dot would be 6.95 microns. (.05 x 139), a 10% halftone: 13.90, 20% 27.80 microns. The smallest thread we make is 27 and 30 microns in diameter which will block some of the dots no matter what angle is used. 

Has anyone out there used Wasatch's hybrid option of halftones that transition to stochaistic below a 15 to 20% tonal value?  Curious if it prints the transition smoothly and fades well into the shirt.

Al

[ZooCity]

The Accurip linearization never worked anyhow, for what it's worth.  I learned to clip dots off and pull back channels to accommodate.  Looking to change this soon by using a better RIP (been "working" on this forever it seems) so we at least know our high/low % that can be held on various meshes. 

Also curious about wasatch's stochastic.  It adds up to me on paper and seems like a no brainer for one of the screens in a 4CP run but I wonder how easy it is to actually implement day to day as well.

Alan, using your math and smallest thread rule, the lowest %age dot one could consistently hold @ 55lpi on a 350/30 or 330/30 or 310/30 mesh would be 7% but I'm guessing open area comes into play here as well?

[JBLUE]

I ditched Accurip long ago after I was told that I did not have to linearize by the owner of it and have been with Wasatch ever since. I will have to see if my version will allow me to print stochastic dots at a certain percentage. I am pretty sure that is only available in the next level above what we have. The only times we run into any issues are around the 4-7% linearized dots. Most of the time though we are killing the 3-5% dots off anyways so not too many problems arise. We do a lot of halftones at 55 lpi as that is our go to with water base and most plastisol.

[jsheridan]

The Accurip linearization never worked anyhow, for what it's worth.

It worked perfectly fine for me when I linearized my R1800 and then the 4800.

Once I dialed in my curve, I was able to hold and print a 3% dot on my 280 mesh.

[Lizard]

Pierre,

Just curious if you are measuring the films or the actual print?  If measuring the actual print what is the standard benchmark?  I know even a two week old squeegee will print differently than a new one and a harder squeegee different again. Or even a different screen for that matter.

[ABuffington]

The lowest percentage math I gave would require all the dots to land completely on the thread so they couldn't print.  It only takes part of the halftone to be over open area to print.  So at a good angle it is possible to image in the 4% range with a high enough mesh count. Also dot shape comes in to play here.  Ellipse dots can span the thread and hit the open area more often than other dot shapes.  Regardless, I have seen round dots curved to print 10-90 with prints that are incredible as well as pushing the envelop to capture the lowest percentage possible.  Capturing the highest percentage possible and printing it well is often harder and may impart more tonal quality than being able to print the low percentages.  The tonal fade of over print to dark fabric is often the wow factor in sim process and can be dependent on how well the base plate captures the finer halftones than the high mesh overprint colors.  Sim process has so many other factors as well that contribute to the overall quality of print that the recipe for one printer may be different for another.  Subjective viewing at typical viewing distances often hides what we think is needed when viewed with a loupe or microscopoe. From pre-press curves to the type of film/imaging solution there is a world of difference in what is printed from one printer to another.  We view Wastatch as a great solution to controlling linearization, plus this transition to stochastic is something to play with and I would see it as a good method to print a gradation that faded out into the shirt to avoid vignette moire and get the fade into black fabric smoother with no moire developing from a low halftone percentage.  I'm testing a new emulsion today with 0-100% tonal ramps and I'll see how this halftone to stochaistic looks on screen. 

We received a Starlight for testing today, thanks Mr. Hoffman, so I will test an inkjet output and see what a 300/34 and 330/30 can hold percentage wise. 

Al

[GaryG]

Al~
What output device are you using?
Thx

[ZooCity]

jsheridan- I think I had a thread on this long ago.  I can't remember all the issues but after working with Charlie, who always provided great AR support, it just wasn't happening.  We were losing data on output v. linearizing the output and I did troubleshoot the heck out of it but never resolved.  4800 as well.

Abuffington- thanks for that, I had the same thoughts on halftone shape/angle.  I like nerding out on this even though you're correct that the finished print viewed at normal distance is the real test, not so much the technical details we tend to focus on.   Let us know what you find on your Starlight resolution v. MH testing!  We still have our MH still setup to test this but haven't been able to for lack of time.  For textiles up to 60lpi the Starlight has easily been "good enough" for us. 

[Sbrem]

For those using Accurip..

the ability to adjust your tonal curve was removed in the last update.. when asked, they said you don't need it.

this just proves how wrong they are.

Well, that's just not right. Thanks, I'll have to remember to not upgrade...

Steve

[ABuffington]

Gary, we have an older 9800 with Wasatch RIP that doesn't have a lot of mileage on it.  The Epson is mostly for testing and custom screens.  Inkjet in any form simply doesn't compare to real film for dot quality.  I will agree with john that it is possible to lose data with linearizations.  But linearization can be repeated after the initial linearization.  I have linearized the Epson printer, output the tonal ramp again, linearized again.  It did correct some of the tonal values that lost dots, or were below the densitometer reading.  In Wasatch you do have 2 calibration curves as well.  Press Curves and Calibration curves that can still be tweaked similarly to how we do it in Photoshop.  this helps fine tune quarter tone values and can help open up the 60-95 range better. It takes all of 20 minutes to print, read and enter the values from a densitometer and improves print quality but then it goes on press and a ton of variables there often mess with good intentions.

Al