Newsprint shops: What Lpi\Dpi settings do you use?

[zen_68]

We are currently using 120\1800 and there is some discussion and debate over whether 1800 is too high of a res for offset presses printing on newsprint. We use an almost new AGFA Advantage N-SA Ctp but have older presses that aren't the best at holding registration. Thoughts?

 

[dabob]

the 1800 is the resolution for the image setter and has little to do with the LPI setting of 120, also the halftone dot size would have little to do with the registration of the printing units . . . best I can do with the information supplied . . . .

 

[zen_68]

the 1800 is the resolution for the image setter and has little to do with the LPI setting of 120, also the halftone dot size would have little to do with the registration of the printing units . . . best I can do with the information supplied . . . .

Sorry, I'm not asking what they are, I'm asking what your settings are. (Prepress workflow) Hopefully from a few newsprint shops, not so much sheet fed or higher quality print shops.

 

[gordo]

the 1800 is the resolution for the image setter and has little to do with the LPI setting of 120, also the halftone dot size would have little to do with the registration of the printing units . . . best I can do with the information supplied . . . .

That is quite correct.

For offset newspaper work a dpi of 1200 for the CtP device is typical.

For the halftone frequency the standard for supplied film, according to SNAP, is 85-100 lpi. (Film is that flimsy clear and black material that was once used when exposing plates).

Some newspapers still adhere to the 85-100 lpi range but there are much better halftone strategies they can use. For example: FM screening (yes even with violet (Auraia II DM as an example)).

The registration issue is probably not the press - it's the web. Have you investigated web growth compensation software? (BTW, one benefit of FM screening is that it reduces the visibility of image degradation caused by mis-registration).

I don't run a newspaper shop but I've set up and trained them to print more effectively and efficiently. You can see snaps taken at my local daily that I shot when I was doing exactly that: http://gordonpritchard.blogspot.ca/2015/01/victoria-times-colonist-newspaper.html

Sorry, I'm not asking what they are, I'm asking what your settings are. (Prepress workflow) Hopefully from a few newsprint shops, not so much sheet fed or higher quality print shops.

Newspaper printing is high quality printing - just like all printing - unless you don't want it to be.

 

[Joe]

100\2400 here for all newsprint. The resolution is dependent on your CTP device. If we try to change the resolution to anything other than 2400 it scales the pages either up or down so we have no choice on the resolution. It has to be 2400.

 

[gordo]

100\2400 here for all newsprint. The resolution is dependent on your CTP device. If we try to change the resolution to anything other than 2400 it scales the pages either up or down so we have no choice on the resolution. It has to be 2400.

That's bizarre (the scaling that is). CtP devices have an inherent resolution (technically an addressability grid not resolution). You should be able to set the dpi that it images at. Setting the output dpi of the CtP should not affect the scaling of input graphics.

 

[Joe]

That's bizarre (the scaling that is). CtP devices have an inherent resolution (technically an addressability grid not resolution). You should be able to set the dpi that it images at. Setting the output dpi of the CtP should not affect the scaling of input graphics.

Blame it on the Swiss. They are Luscher CtP units. I didn't believe them when they told us that so I tried it and the images do scale. Though that was 8 years ago when I tried it. They might have changed something along the way with updates and I haven't tried it since they were installed new.

 

[kineticnrg]

As mentioned above the prepress / cap may not be the problem. When do you notice the registration issue? Do you have good registration when you put on a new roll; then have issues as the roll reduces in size during the press run? How are all your blankets and mylars on the colour units?

We find it best to change all the blankets and mylars at the same time, even if only one is "damage". We also use and "automatic" braking system that helps keep constant tension during the press run. This two items have help a lot. If possible check proper press specs setup and if you are not running to specs, try that out.

 

[zen_68]

As mentioned above the prepress / cap may not be the problem. When do you notice the registration issue? Do you have good registration when you put on a new roll; then have issues as the roll reduces in size during the press run? How are all your blankets and mylars on the colour units?

We find it best to change all the blankets and mylars at the same time, even if only one is "damage". We also use and "automatic" braking system that helps keep constant tension during the press run. This two items have help a lot. If possible check proper press specs setup and if you are not running to specs, try that out.

Thanks. The registration issue is a web tension \ brake issue. We know whats causing it, just don't have the resources or space to fix it atm. Do you print on newsprint? What are your Lpi\Dpi settings?

 

[kineticnrg]

We print mostly on newsprint and we print at 120lpi for colour pages.

 

[SteveSuffRIT]

A few thoughts:
1) Low CtP spi allows faster RIP processing speeds. Want to make plates quickly. Higher spi will slow down throughput speed.
2) Low spi and low lpi produce less gray levels. 120/1200 = 10^2 = 100 gray levels.
3) Low lpi accommodates inexpensive groundwood newsprint, 24lb, 0.002". Prevents shadow plugging-up and filling-in and holds min/max dot.
4) Low Lpi helped minimize 26% TVI @ 50%, coldest ink are low viscosity and spread into absorbent uncoated newsprint
5) ISO 12647-3 is for coldest newsprint
6) IFRA is the trade association for newspapers

Steve Suffoletto (Buffalo/Rochester, NY)

 

[gordo]

A few thoughts:

2) Low spi and low lpi produce less gray levels. 120/1200 = 10^2 = 100 gray levels.

Out of date formula that has not applied to halftone screening since around 1990. The formula is only true for the tone represented by a single, isolated, halftone dot based on an individual halftone dot cell - something that never occurs in real production environments. (A full explanation is here: http://the-print-guide.blogspot.com/.../Grey%20Levels )

3) Low lpi accommodates inexpensive groundwood newsprint, 24lb, 0.002". Prevents shadow plugging-up and filling-in and holds min/max dot.

Newspapers and flier/insert are reqularly printed with high lpis and FM screening. Shadows plugging are effectively dealt with using dot gain compensation curves.

4) Low Lpi helped minimize 26% TVI @ 50%, coldest ink are low viscosity and spread into absorbent uncoated newsprint

Desired TVI can easily be defined using dot gain compensation curves.

Here is a link to just one coldset newspaper press that's been printing its dailies using FM screening successfully (actually Auraia II DMS) for about the past 6 years: https://gordonpritchard.blogspot.com...newspaper.html