DPI for screen printing?

austin · December 04, 2004, 06:07:03 PM

Hello, I'm going to have a screen print made for an effect. I've done the layout already at 100 dpi, but I don't think it'll be good enough. Of course, the image file size shoots way up when upping the dpi. What dpi do I want for a professional quality print? TIA.

1wahfreak · December 04, 2004, 06:30:48 PM

DPI is generally not the way screen printing is measured unless you are printing halftones. If you are just printing solid colors, the screen mesh makes all the difference. The finer the mesh, the better the print quality. However there is a threshold. If you try to squeeze too much ink through a very fine mesh you will not be able to transfer all the ink (with one print pass) through the screen. It's a balance between mesh and ink viscosity.
A 300 mesh would be fine for printing solid colors.
If you are printing halftones, use a finer mesh, maybe a 350 would be the best choice. However 100 lines per inch is probably too fine for the exposure unit to accomplish. It all depends on the type emulsion, emulsion thickness, light intensity and time of exposure.
What is it exactly that you want to print?

austin · December 04, 2004, 07:08:28 PM

I'm going to printing only one solid color using an epoxy ink. The ink will either be going on bare aluminum or a clearcoat over the aluminum. The smallest font I have is 10pt at 100dpi. Is there a difference between lines per inch and dots per inch?

I might not have been completely clear in my first post... I'm not making the screen, I just need to make a graphics file to give to the screen makers. I'm not sure how anti-aliasing effects the screen making. At 100dpi, with anti-aliased fonts, it looks pretty good. If a screen is made from this image, I think it will lose the anti-aliasing information and look blocky. Should I just use 300 dpi?

1wahfreak · December 04, 2004, 07:42:00 PM

Somebody correct me if I'm wrong but DPI and LPI (lines per inch) are not the same thing. DPI results in how fine your letters will be. You'll will end up with much crisper letters in your art work if you use 300 DPI vs 100 DPI. LPI is the amount of lines per sq inch that the printer can print. A 300-600 DPI laser printer can usually only print at an LPI of 50-65. Sounds confusing I know. We use some pretty powerful stuff at work which turns out art work at 4000 dpi. This makes for great looking art, but if your only printing at 25 LPI at the printer, it may be a waste.
I would use the highest resolution you possibly can for your art unless for some reason higher res. means more cost to you. That way, the printing screens should turn out better which means your end product should turn out better. Make sense??

austin · December 04, 2004, 08:38:37 PM

Got it. Thanks.

arielfx · December 04, 2004, 09:05:41 PM

If you are not making the screen than you should have the file in good quality. When I did my first screen I was asked for 300dpi+ files... It doesn't really matter because the net you will use is just over 100dpi.

G Kresge · December 04, 2004, 09:10:24 PM

The best thing to do would be to create a vector image of the lettering/graphics in an application such as Adobe Illustrator and convert the text to outlines. This will give you the sharpest image quality when the screenprinter makes his film positive for the screening process. If that's not an option, I would recommend a 600 dpi bitmap image for your file resolution. I may not know much (if anything) about electronics, but I have been involved in graphic arts and screenprinting for over ten years.

arielfx · December 04, 2004, 09:38:28 PM

i agree, vector format would be the best! if you'll ever want to do engraving as well these types of files can be used!

austin · December 04, 2004, 11:17:59 PM

Thanks all - I'm using The Gimp for image software and I don't think it does vector graphics. 600dpi is going to be a huge file, but I'll go ahead with it to make sure the quality is there.

arielfx · December 04, 2004, 11:22:30 PM

i'm not sure about this but i think that paint shop pro can open your file and save it in a vector format.

bigjonny · December 05, 2004, 02:44:50 AM

Quote from: G KresgeThe best thing to do would be to create a vector image ... If that's not an option, I would recommend a 600 dpi bitmap image for your file resolution. I may not know much (if anything) about electronics, but I have been involved in graphic arts and screenprinting for over ten years.

I'll chime in on this too. I've been doing screen printing since 1988 and G Kresge is absolutely right.

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DPI for screen printing?