Prepress advice needed

Robert carter

Well-known member
I've been in the printing & sign business for 35 years and now am semi retired. I set up a small shop in my basement to piddle around in, when I had my shop, I used metal plates and then silermaster plates. But now I might go a couple of weeks and not print anything, and I find myself wasting a lot of chemicals. I've tried bottling them up. I was thinking about those laser plates, I got some samples from Valley Litho and had some moderate success. I want to be able to print pretty good quality. Is there a laser plate ( Poly/Paper) out there that will give me decent quality? I am using Illustrator/Photoshop
HP 8000n Postscript printer. Any help would be greatly appreciated. Thanks Robert.
 

Stephen Marsh

Well-known member
How many colours are you printing?

What are your tolerances for registration/trapping?

Is it mostly text/linework, or halftone?

If halftone, what expectations on linescreen do you have? Do you have expectation of over say 85 or 100lpi?

Google the following keywords, there are many options out there:

offset laser polyester plates


Then take a look at alternative systems, such as:

CTP Solution / Kimosetter 410 / KIMOTO CO., LTD.

or

Epson Stylus Pro 7900 Computer To Plate Professional Imaging System

Do the ROI, it may even be better to outsource plate production.

In all cases, perform live trials using the supplier test plates or even better, get them to RIP and supply plates with one of your common jobs.


Hope this helps,

Stephen Marsh
 
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Robert carter

Well-known member
Mostly line work with the occasional halftone, more often will have type and line with percentage screens (10%-15%?) I want a plate that will reliably hold these screens. I am also having trouble reducing the dot size in these screens in illustrator. any help would be appreciated.
 

Robert carter

Well-known member
When making halftones I make the photo grayscale and then apply the color halftone filter with 4 pixel size and the pic prints out too grainy.
 

Stephen Marsh

Well-known member
When making halftones I make the photo grayscale and then apply the color halftone filter with 4 pixel size and the pic prints out too grainy.

In my experience a PostScript printer driver’s halftone engine creates better dots than doing this upstream. So print to separation from say InDesign using your HP laser printer PS driver using appropriate halftone settings. Just have your images in regular grayscale or colour with no halftone filter applied, the driver will halftone the separations on the fly at print time (with better results).

Robert, IMHO if you wish to do this upstream and not on the fly at print time, you should be going from grayscale mode to (binary) bitmap mode in Photoshop, then selecting halftone screen (say 85lpi, 45°, round) and not using the contone halftone filter.

You may need to apply “drastic” tone compensation curves to your images before doing this depending on the linescreen ruling (to lighten them, otherwise you will have mud in your midtones to shadows). Your images will also need to be resized to the final reproduction size and placed in layout software at 100% magnification only.


Stephen Marsh
 
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Stephen Marsh

Well-known member
It is great (for me) not having to worry about creating good laser printer dots for a Silvermaster or similar anymore!

Attached is a screen capture of the HP PostScript laser printer driver settings that I was talking about when printing from InDesign as separations to a PS printer.

You may wish to go lower than say 85lpi to get a good dot that is “clean”, even when printing at say 1200dpi. You may need to experiment with say increments of 5lpi etc.

Additionally, the “paper type” may also play a crucial role, for this demo I was only using plain uncoated copy paper, a poly plate would likely need a different setting (again testing is required or the plate supplier may have a suggestion).

NOTE: I elected to use an 85lpi screen, however the driver defaults to 70lpi which may be for a very good reason.


Stephen Marsh
 

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Stephen Marsh

Well-known member
Attached are USB microscope photos of a 1200dpi laser print of a 5% (left) and 20% (right) flat tint from InDesign (linear tint data, no curve applied).

The upper image is from the printer driver and InDesign creating the halftone “on the fly” from 8 bpc “contone” data.

The lower image is from a Photoshop Grayscale mode to Bitmap mode conversion, using 1200ppi, Round dot halftone, 45° angle and 85lpi screen ruling. This method requires more work and is generally less than ideal when compared to the printer driver method.

Remember, these are only flat tints, gradients and images will be slightly different. From my experience, the dots were generally better from the printer driver than doing it manually upstream in Photoshop.


Stephen Marsh
 

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Robert carter

Well-known member
That was exactly what I was looking for, thank you Stephen and thanks everyone else for for your help. Now I will figure out which type of laser plate to use.
 

tastar

Member
There are some new inkjet direct-to-plate systems - DAA International has a few different systems starting at 13 inch wide inkjets with a RIP and polyester plates that will do up to a 150 line screen - at this link. And, Presstek and MarkAndy have reasonably priced JT inkjet plate systems that use Epson printers, a RIP and metal plates - at this link and this link.

Tony
 

discountprinting

Active member
I use both the plates tastar mentioned and they both work well. I run very high quality 4 color process at 150 lpi @ 1440 dpi daily using the GenieJet plates and use the JT Direct when I need a longer run length plate.
 

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