Archived posting to the Leica Users Group, 1997/11/29
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Steve: You are confusing a few things that are different, but sound the same. DPI: Dots per inch that a printer can resolve PPI: Pixels per inch in an image data file LPI: Lines per inch of the dot screen on the printed image. Perhaps you know about the printing process, so forgive me if I'm talking down to you. Just to give you some benchmarks, a newspaper uses an 85 LPI screen for it's pictures. A newsletter or tabliod on uncoated, but finished paper might be at 100 LPI. Most magazines are printed with 150 LPI halftones and color seps (but the range is 133 to even 200). An image printed on a good sheetfed press at 200 LPI look like photographs. Back to printers. A 600 DPI printer can resolve enough dot to render a 90 LPI halftone pretty well, but not perfectly. At 720 DPI, with good paper, you can get a nice clean 90 LPI Screen. The dot and edges will be crisp, but the image will have a clean grainy look. The new 1400 DPI printers can make a 150 LPI image, which is to say, as good as magazine repro. Keep these numbers in mind: 600 DPI printer: 85 line screen (LPI) 720 DPI printer: 100 line screen (LPI) 1400 DPI printer: 150 line screen (LPI) Now, you need an image file that has a PPI of about double your target LPI. (You can often get by with 1.5x.) So, a 600 DPI printer needs a 170 DPI file. A 1400 DPI printer, like the Epson Photo needs a 300 PPI file. That gets us here: 600 DPI printer: 85 line screen (LPI), 170 PPI file 720 DPI printer: 100 line screen (LPI), 200 PPI file 1400 DPI printer: 150 line screen (LPI), 300 PPI I hope this helps. But plan to be confused, because those of us in the business refer to all of them as DPI, because we're lazy and we know that when we are talking about files we mean PPI and halftones & color seps we mean LPI. Tom At 08:57 AM 11/29/97 +0000, you wrote: >Jim, you say that you need the same dpi for inkjet and other digital >printers. I have heard that it is 1/3 the dpi. Epson says 240 dpi for >the 720dpi pro stylus, the guys that do the big Novajets and others want >a 100 dpi file for their 300 dpi printers. >Not wanting someone to waste their harddrive and storage and printers >time, >Steve > > >