Grid pattern in screens

Hi all,
Second post for me. Seriously big thanks to member Martin Mueller for some really good simple advice with the last one!
Before I go any further I would like to very respectfully say that I'm not looking for advice that ends with "buy some RIP software" or "get a denso" or a mega complicated lesson on spectophotometry.
I'm a simple man (trade qualified) with a GTO in the garage, not a 10 colour speedmaster and a spare million bucks
We're running positive film out of a middle of the range inkjet printer without a RIP and getting really nice results.
Until we try to run a decent screen..........
My graphic designer (read: mate who I used to print newspapers with) manipulates our images in Photoshop and sends me a PDF. Whenever we try to produce a tone we end up with dots that aren't round and patterns through the screen.
Most of my work is low end stuff on 80 gram bond so we're not trying to achieve anything super special.
These a couple of (poor) photos attached to give an indication of the issues that we're having. We ran our first 4 colour yesterday and were quite happy with the result, except for these damn patterns through the image.
Any input will be greatly appreciated.
Many thanks in advance.

 

Hi Travis,

first of all, thank you for compliments
The PDFs that your mate creates in Photoshop and which you then print on the Canon Pixma TS8260, have they been rasterized with Photoshop?
If you can already see these raster phenomenons on the monitor, they will come from Photoshop´s rasterization settings. Try out other different rasters, or screen settings in Photoshop. Photoshop is able to generate homogeneous screenings.
If the Photoshop PDFs are okay, it might come from the Canon printer driver.

 

Thanks for your reply Martin. I won't keep flattering you but I definitely appreciate your opinions.
I sat down with the designer yesterday and watched what he was doing to manipulate the images.
He was rasterising the images by setting them as halftone in Photoshop and (of course) setting the dots to the 'round' setting. When we zoomed in the dots were terrible! They were anything but round. Particularly in areas with a greater than 50% screen they were square and crosses etc which is exactly what is showing up on the plates/print.
I said 'fix it or I'm not buying any more beer' and he said he's basically out of ideas.
He then took the original image without manipulating it and selected 'print' and changed a print setting to 'seperations' and ran it out of his cheapo laser printer. It rasterised them automatically and printed out four seperations with perfect dots in the screens at quite an acceptable resolution. We were absolutely ecstatic. We then connected my Canon inkjet and attempted the same thing without changing a single setting. It printed the four seperations but the dots were frequency modulated and had colour in them making up the black.
I did notice that photoshop had a setting to control the printer independently of the printer driver so that will be my next avenue of investigation.
I've taken the plunge and purchased a later model laptop and subscribed to the adobe suite as I'm starting to lean on my mate too much and it's pretty hard to run a print shop without it anyway.
Any and all opinions most welcome.

 

Hi Travis,

For what you describe I can give you some explanations.

The printout on your designer's laser printer provided well-screened separations. Even this "cheap" laser printer will probably have a Postscript interpretation (RIP, Postscript driver) and can therefore output raster points correctly.
The situation is different with your Canon printer. The printer produces what an inkjet printer, which always produce only with Windows / MAC printer drivers, an FM raster.
All in all, it shows you the need for RIP software tailored to the output device. The RIP performs the interpretation and sends the rasterized print data to the optimally addressed output device (inkjet printer).

 

I have replied to another thread about inkjet film. Then I remembered that I actually ran laserjet film for a couple of years with very good results.
The main problem I had with it was that for 4 colour work (which is why I bought an old GTO 46 single colour) the plates were dimensionally inconsistent. An hp 5000 or 5100 prints excellent linescreens up to more than 150lpi. Funnily enough I found the Hp 5000 was more accurate than the 5100. It actually may have been accurate enough. You can buy a spray which makes the toner more dense but I mostly did not use it.