The subject was black and white printing, but since colour halftone dot patterns should even be less noticeable, I think the advice can be extrapolated. So your question can be distilled down to: what is the minimum LPI halftone screen I need so that it's not distracting at the distance the poster will be viewed? I did a little searching, and actually found a research paper on this subject. Because of high-speed printing and cheaper paper/printing of newspapers, they are often as low as 85 LPI, so you can see the individual dots easily on the funny pages. Why are most things printed at 133 or 150 LPI? Because at reading distance for CMYK printing the dots aren't generally discernible. The rule of thumb is that we need 1.5 to 2 times the LPI in PPI to get acceptable results. Why? Because most raster artwork is printed with CYMK processes at a maximum (generally) of 150 LPI.

for clean text resolution)' - here you're confusing DPI with PPI (often done.) Raster artwork for print is generally scanned at 300 PPI. Now you said 'As i understand it 300 DPI is the typical for 'small' artworks (esp. PPI = Pixels per inch = the number of pixels per inch in screen/scanner file terms.LPI = Lines per inch = The offset printing 'lines' or dots per inch in a halftone or line screen.DPI = Dots per inch = units used to measure the resolution of a printer.

Here's definitions, so we know what we're talking about. I like the accepted answer, it has good advice, but I thought I'd expand on it a bit.įor wall sized graphics and large banners (e.g 3m x 5m), what is an acceptable PPI/DPI for print.

Minium resolution for picture sizes