6 Replies Latest reply on Jun 17, 2014 2:28 PM by Daniel Flavin

    Obtaining correct line screens

    jason t Level 1

      Hello all, hopefully someone understands this technical issue and could shed some light on the subject.

       

      I work for a newspaper with an old web press.  We have an HP LaserJet 5100 PS printer that I can easily set an 85 line screen (LPI) option and receive correct output.  I need a replacement printer but I am having a lot of trouble finding one.

       

      I tried a Xerox phaser 7500 dn but when I set the 85 line screen it comes out very fine (small dots - 85 lpi is quite coarse).

      I tried an HP LaserJet 2055 that has ability for custom line screens but again when I say 85 lpi I am not getting the same output as the 5100.  In fact this 2055 has a 60 lpi option, but the dots it produces are much smaller than the 85 (they should be bigger)

       

      I don't clearly understand all there is to about LPI and DPI.  Does the output resolution of the device affect the line screen?  If so, how do I calculate a new LPI based on the output resolution?  What do I need to look for in order to purchase correct hardware?

       

      I was told both options above would do what I want but neither do.  HP Tech support operators really don't understand what I'm talking about and keep telling me half their printers have custom line screen options but I doubt they will work (I purchased the 2055 after they told me it would).  HP advised me to contact adobe as that is the software I'm printing from - though I'm sure its the device, not software with the issue.

       

      We are slowly moving to outputting directly to film with our imagesetter but we still need to have a functioning PostScript printer for backup.

       

      Thanks in advance -

      jason

        • 1. Re: Obtaining correct line screens
          Peter Spier Most Valuable Participant (Moderator)

          In order to be able to set custom linescreens you need the ability to set the number of printer dots per screen spot, and not all values are possible, especially with lower-resolution devices. Back in the dark ages I used a 1200 dpi Xante Accelerwriter with Quark and in theory I could set custom screens in the print dialog, but in practice I only got one or two actual changes. I expect you'll need a printer with postscript and at least 1200 dpi, and a driver that lets you set the screen.

          • 2. Re: Obtaining correct line screens
            jason t Level 1

            thanks for the info - that lines up with what I see when I'm outputting to the imagesetter - it only allows certain screenings at certain resolutions (the dropdown for screening lists the possible combinations) and rejects jobs that don't fit.

             

            On the HPs, there are only 2 line screens listed in the dropdown (neither are 85) but when I manually specify this it works on the 5100 but no other.

             

            I realize I need a postscript printer (and the driver along with it) but after getting two of them, I see it's just not that simple.  I could look for a higher resolution device - would you know of any way I could confirm it will produce the intended output without purchasing it first?

            • 3. Re: Obtaining correct line screens
              Peter Spier Most Valuable Participant (Moderator)

              I'd ask the sales department for a print sample made from your file, if possible. Be very clear that you will not buy a printer that cannot produce the 85 line screen, and that if they need to enlist help at the manufacturer to test this, then they should do so.

               

              And how did you verify the screen on the old HP?

              • 4. Re: Obtaining correct line screens
                jason t Level 1

                well - it technically hasn't been verified....

                 

                the guy that converts our negatives to plates is from the previous iteration of using meshes for screens and filters for separations.  I take his word that what is output (set at 85) is really 85. 

                 

                Aside from that, I can only see that the 'correct' 85 from the old HP has huge dots while everything else is super fine (1/5the size).

                • 5. Re: Obtaining correct line screens
                  Peter Spier Most Valuable Participant (Moderator)

                  You used to be able to buy a little gadget with ruled converging curves called a screen finder that you superimposed on a halftone and read the linescreen at the point where an interference pattern was created. Not overly accurate, but good enough to tell the difference, I think, between 65, 85 and 105 lines.

                  • 6. Re: Obtaining correct line screens
                    Daniel Flavin Level 4

                    Peter Spier wrote:

                     

                    You used to be able to buy a little gadget with ruled converging curves called a screen finder that you superimposed on a halftone and read the linescreen at the point where an interference pattern was created. Not overly accurate, but good enough to tell the difference, I think, between 65, 85 and 105 lines.

                     

                    I have an one or two...pretty cool.