200 line screen with film

[Prepper]

We have just this year changed our sheetfed work from 150 to 175 line on coated stock. We are now considering trying 200 line screen. My questions are being film based still, is this too high and if not should we continue to output at 2540 resolution on the imagesetter or increase the resolution and if so to what, 3386 or higher?

Thanks,
Terry

 

[gordo]

Re: 200 line screen with film

Whether you need to up the resolution on your filmsetter to go to 200 lpi will depend on the halftone screening system being used. Screening that uses supercell technology (most modern screens) will not need the extra resolution.
You will need to apply a dot gain compensation curve though. If you are using the film to also image your proofs you may get a disconnect between proof and presswork caused by the curved film being appropriate for plating but no longer for proofer.
You may also have to increase draw down times in the vacuum frame. Check the consistency of plate imaging in your vacuum frame using film with screen tint patches of at least 1, 2, 3, 4, 5% and 95, 96, 97, 98, 99 and 100% placed at each corner and centers of the film.

best, gordo

 

[John W]

Re: 200 line screen with film

If you screened your 175lpi at 2540, you are already near the limit of having enough resolution data to map completely over the screening ability. If you screen finer yet, you are only making the rosettes smaller to the naked eye and not really achieving all the extra data possible from a higher resolution rip.

We run our 175lpi ripped at 3386 and through testing have proved that there is more detail in the jobs.
For stamp work, it would be useful to rip @ 4000. But this is terrible dependant upon the rip you use and the screening system it uses.
I would think that 10 micron stochastic requires optimization for output. Most setters are optimized for 150lpi at 2400, or 2438, or 2540 depending on the output engine. I am aware that some devices cannot handle 10micron stochastic while others can.
John W

 

[gordo]

Re: 200 line screen with film

As a side bar - since you brought up the issue of stamp work - Canadian stamps have for years been printed using Kodak 10 micron Staccato (hybrid stochastic) screening.

best, gordo

 

[Prepper]

Re: 200 line screen with film

It's a Xitron (Harlequin) rip, just using their HPS screening, nothing fancy. So you're saying we would get better detail at 3386 whether 175 or 200lpi?

I was just wondering because I've been seeing a lot of people say they're running 200 on coated and 175 on uncoated and wondered whether that was higher now because of CTP and whether that was too high or pushing it for a film based shop?

Thanks,
Terry

 

[zoran]

Re: 200 line screen with film

..and they are done on Creo Trendsetter @2400 dpi.
Not just Canadian but bunch of international as well.

 

[John W]

Re: 200 line screen with film

Xitron HqRip. Same set up as we use. My tests show that a higher resolution ripping produced better gradients, richer detail in general. We are convinced from actual testing including printing of those tests, that variable resolution setters (such as Screen) give us higher quality work over fixed resolution output engines. That is not to say that the fixed engines do not work, of course they do but we found even better quality with higher resolution for; type, small images with high detail in them, spectral highlights, weaves etc. However you also get better reproduction of moires, dirt etc so one must be careful. Plus the higher resolution takes longer of course and is perhaps then not suitable for some work. Be careful because some vendor's engines use an emulated higher resolution not an actual; I believe those fakers double the lower resolution values to simulate the higher resolution. I have not tested those machines.

Now we use two resolutions and two screen rulings for all our regualr work. Many of our clients have been shown the difference and are seemingly happier with the extra value.
Cheers,
John W