Highlight dot dropoff in highlights

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Highlight dot dropoff in highlights

Postby polybean » Fri Jun 21, 2013 11:26 am

Hi, wondering if anyone has any ideas how to prevent highlight dot "dropoff". See sample attached, the other file shows the dgc applied to the job. I'd bumped the highlights initially because they had been dropping out, but I'm wondering if I need a separate dgc for gradations. Thanks in advance for any comments.
Attachments
DGC.jpg
dot gain curve
DGC.jpg (248.09 KiB) Viewed 8539 times
highlight_dropoff.jpg
sample showing gradation with dropoff
highlight_dropoff.jpg (731.74 KiB) Viewed 8539 times
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Re: Highlight dot dropoff in highlights

Postby angelius » Tue Jun 25, 2013 5:11 am

Hello,
IMO this is not a good dgc for flexo prints, depending on your anilox LPI, flexo plates you use, material you print on of course the dot gain curve changes.
But bumping a 0.39 dot to 3.63 0.78 to 4.47 1.18 to 5 and 2 to 6.28 is not a correct curve.
First of all without a curve implementation with HD flexo plate test charts (or what you have available), you should find out what your min dot is on plate, than measure what is your printing curve and according to measuring results you should change your curve.
This screenshot you have send is from Intellicurve and/or Curvepilot. This means you probably have ESKO CDI in CTP with zero oxygen effect on plates. You dont have to bump highlights this high, it is too much for flexo even at 133lpi printing conditions.
And according to this curve you implement, your gradients cut at 3.63 like a razor.
If you tell me these values, I ll have more things to say.

Printing device and anilox for highlights----> anilox LPI
Min dot on non-curve implemented test plate -------> %1? %2? %3?
Measured solid density-----------------> i.e Cyan %100 area 1,50
Again with linerization test plate measure ----------> at least measure these %90 %80 %70 %60 %50 %40 %30 %20 %10 %5 %4 %3 %2 %1
After all these, we ll talk again, PM me pls.
Thx and take care.
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Re: Highlight dot dropoff in highlights

Postby webchem » Mon Sep 16, 2013 5:32 pm

What you're seeing is the standard behavior of digital flexo plates made in the presence of oxygen, which require a 'bump' curve in order to generate a stable minimum printing dot. This is pretty much inescapable with standard digital flexo plates, although obviously people have gotten very good at working around this limitation and printing well. I'd agree with the previous post that you could likely refine your curve a bit more and get a smaller minimum dot.

Another option would be to try a technology like MacDermid's LUX, which largely eliminates the bump curve, and produces a flat-topped dot shape that has other advantages in print consistency. You might be able to print a few points lower, and it will be easier to reproduce from run-to-run. You'll still have to set a dot gain curve and all, but you won't see highlight dots up to 4-5% simply failing to exist when made from a linear tone scale.

Full Disclosure: I am MacDermid. Well, at least part of us.
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Re: Highlight dot dropoff in highlights

Postby mladen » Sat Oct 05, 2013 11:09 am

hello

The curve is made OK in Intellicurve software.
You dont need second curve.
You must use some of hybrid screening for higlight.
With AM screening your result is good, according the picture, and it can not be better with AM.
Recommended Hybrid screening ; quantum, autoblend, sambaflex , custom Perfect highligts from ESko..or use FM or staccato or monet completly without bumps in higlights.

BR
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Re: Highlight dot dropoff in highlights

Postby guy de cafmeyer » Tue Dec 06, 2016 2:55 am

Just in case anyone decides to read an older post ; re. highlight dots dropping off ;

You can do 2 things ; In repro , you should "noise" the finer dots , in effect spattering the dots apart ... so that the end of the vignette kind of disappears . Also , you need to look at your cell shape on the anilox . The hexagonal is best , so that minimum dots don't disappear randomly , especially if you have noised the vignette , and this cell shape allows for more cells in a given area , opposed to say the E cell ( elongated cell ) . The longer or larger the cell , the more problems you will have with finer dots , due to the surface tension of the inks ... seen as dots missing randomly , etc .
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Re: Highlight dot dropoff in highlights

Postby richflexo » Fri Feb 17, 2017 12:58 pm

Hi, just a thought. I notice your "Keep 0%" is still 0%. I suggest making it .8%
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Re: Highlight dot dropoff in highlights

Postby guy de cafmeyer » Tue Feb 21, 2017 3:36 am

Good point by richflexo .
A minimum dot needs to be maintained , as your plates cannot hold ( for example ) a dot size of 20 microns .
So for 120lpi plate , should have a minimum dot of 1 % .
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Re: Highlight dot dropoff in highlights

Postby Acmegv » Fri Jun 02, 2017 9:51 pm

No matter what you do you with AM screening you will see a hard edge. The best solution would be HD screening, next would be to use sambaflex, but if you do not have these screening licenses the cheap solution is to create a dithered bitmap and use it to knockout the highlight end of the screen. You will get some particle dots but it can be an effective solution.
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