Screen problem with Prinergy

[MGERTI]

Hello everyone,

I use Prinergy 5.1 and a new one Trendsetter from Kodak. Everything looked Ok in the beginning but suddenly i recognized a screen problem( this is what i think). After printing the plates that i produced i see this strange effect. It looks like moire but i'm not sure about it. The dot shape is not correct what i think. I can see it with my own eyes without using a magnifier glass. The support from Kodak supposed that the head has to be cleaned. They did it but the effect is still the same.
This effect is visual to all my clients with different printing machines. I tried to change the screen angles but this is not allowed in Prinergy. I had the same problem with Dolev 800V years ago and i solve it by increasing the screen angels by 5 degrees. Now i'm using +7.5 degrees angels in prinergy. The effect is again but not as in the beginning. the Images are not sharp and clean as they were when i started working with Trendsetter and Prinergy.

Hope you have an answer about my problem

 

[gordo]

Hello everyone,

I use Prinergy 5.1 and a new one Trendsetter from Kodak. Everything looked Ok in the beginning but suddenly i recognized a screen problem( this is what i think). After printing the plates that i produced i see this strange effect. It looks like moire but i'm not sure about it. The dot shape is not correct what i think. I can see it with my own eyes without using a magnifier glass.
[SNIP]I had the same problem with Dolev 800V years ago and i solve it by increasing the screen angels by 5 degrees. Now i'm using +7.5 degrees angels in prinergy. The effect is again but not as in the beginning. the Images are not sharp and clean as they were when i started working with Trendsetter and Prinergy.

I'll let Kodak support their product, however, for clarity's sake, standard photomechanical screen angles (75 and 15/105 degrees can cause a type of patterning called single channel moiré to occur. Shifted angles were developed to avoid this problem. The angular distance between angles remains more or less the same: however all the angles are shifted by 7.5°. Shifting by 7.5 degrees introduces "noise" into the screen pattern which eliminates this single channel moiré.

So, if you are experiencing single channel moiré (which I very much doubt) then shifting the angles 7.5 degrees will eliminate the issue. But as you say it doesn't so again that points to a different problem.

best, gordo

 

[airyk]

by chance did your dot shape get changed in your prefrernecs?

 

[tcollins]

possible solution

possible solution

I have been using Prinergy for 9 years now and we had a similar issue many years ago, we did some tests and found that if you use Maxtone CMYK 105-45-90-75 as the Screen System and EllipticalIP as the Dot shape this fixes the issue with the moire type patern in teh screening, also we found that using 150 line screen made it look worse so years ago we changed to 175 line screen and now we are using 200 line screen and we have not had an issue for years.

hope this helps.

 

[gordo]

I have been using Prinergy for 9 years now and we had a similar issue many years ago, we did some tests and found that if you use Maxtone CMYK 105-45-90-75 as the Screen System and EllipticalIP as the Dot shape this fixes the issue with the moire type patern in teh screening, also we found that using 150 line screen made it look worse so years ago we changed to 175 line screen and now we are using 200 line screen and we have not had an issue for years.

hope this helps.

Swapping the Magenta and Black screen angles does not/will not solve the OP's problem and I doubt it did anything to solve whatever problem you had.
Maxtone is the same as Prinergy's AM screening except for the ~1-3% and ~97-99% dots which do not get any smaller than the minimum dot size specified.

Also, 150 lpi is an even divisor of 2400 dpi-and therefore is unlikely to create either the OP's or your problem.

best, gordo

 

[gig0]

Is there an intermediary device between the Prinergy box and the Trendsetter, such as a Brisque?

 

[MGERTI]

Prinergy

Prinergy

Thank to you all for your answers.

The kodak support made some test and they don't call it "moire" but "structure" or "pattern".
They say that my printings are ok for them. But for me is not. Why this effect wasn't from the beginning. it can't just happen i think.
There are two Brisque-s in my office LAN but they were from the beginning when i installed Prinergy. So i don't think that they are the problem.

Gordo,
What i really see in the printed sheets are some diagonal lines, when magenta and yellow are mixed creating orange and in skin tones. If the head of the Trendsetter is OK and the whole machine is in perfect conditions i really doubt about the Prinergy.
From your experience what might be the problem? I tried all by changing dot shapes and screen angles and the problem is the same. Is there any possibility that prinergy might be "corrupted" and it needs a re-install? Or it is a Refine problem?

 

[gordo]

Gordo,
What i really see in the printed sheets are some diagonal lines, when magenta and yellow are mixed creating orange and in skin tones. If the head of the Trendsetter is OK and the whole machine is in perfect conditions i really doubt about the Prinergy.
From your experience what might be the problem?

The most obvious problem would be a moiré caused by the Magenta screen angle conflicting with the Yellow screen angle. That would mean that your Magenta would have to be 15° away from Yellow. Are your Cyan and Magenta screen angles swapped? I.e. if the standard angle set is 15°C, 75°M, 0°Y, 45°K are your angles 15°M, 75°C, 0°Y, 45°K instead? Another thing to check is the ink hue of the Yellow. Is it dirtty, or contaminated, or a special fade resistant Yellow? If so, a darker Yellow will increase the visibility of the natural moiré.

A more remote possibility is if you are using an Elliptical dot shape (e.g. EllipticalP) try switching to a Round dot (not Euclidean (round square round)). Elliptical dots link up between the 40% and 60% tones forming lines which you might see if you've got very good eyes. The lines would appear as diagonals since the Magenta screen is at an angle.

best, gordo