Platinum Printer Member
- Dec 20, 2010
- Reaction score
- Ottawa, CANADA
- Printer Model
- Canon Pro-100, and Epson 3880
Everybody assume that everyone else knows the difference between DPI and PPI. !
Well their assumptions can be very wrong and varied, but as most are not exactly sure, the subject tends to get glazed over by introducing even more technical issues thrown in to mask their own discrepancy’s.
PPI is indeed Pixels Per Inch, which is specific to Digital imagery and equipment, and most tend to get that bit right, and it should never be confused with DPI, but what about DPI ?
Again here nearly everybody gets this wrong, and with a commanding voice they’ll say, “You meant PPI don’t you.” (This subject has been cover already in some detail.)
But DPI was used mainly for Image Reproduction in the Printing and newspaper trade back when Adam was still a boy, it’s still used in scanning and RIP Laser printers, but never in Inkjet printers. (Using a Loupe on a laser printed sheet to see these pesky little dots clearly), 300 DPI can’t not be seen clearly by the human eye and so was used as a Standard.
Lastly we come to LPI, so what the hell is that used for, ask and you are guaranteed to be told wrongly, it now stands for “Lumosity-Performance-Index”, because (Wikipedia) says so, but it meant something very different to the Printing industry.
Back then it was used to convert halftone screens to a pattern of dots for every known publication, the term LPI, was in fact Lines Per Inch for a given image and was used for perfect reproduction, and DPI was measured as 1 ½ times LPI.
Newsprint used 65 LPI, Standard leaflets used 85 LPI, Brochures used 100 LPI and magazines used 133 LPI, because each publication used different paper surfaces, and to hold a good open dot in an image each publication used a different LPI screen.
it’s still much the same on the average Inkjet printer today, use too porous a paper surface or too high a print setting and the dots will merge to eliminate the white area around them giving a much poorer print to what was originally intended, it’s now known as bleaching.
So ends the Rant...
Now back to Printing Various Size Photos to 8x10 ! !
Agree 100%, and mainly because I too come from a commercial print background and understand your figures. (Offset - web and sheetfed)
However inkjet printer manufacturers also like to muddy the waters. My Epson 3880 manual p133 states: Maximum resolution 2880 x 1440 DPI. This is also mentioned in more than one place in the manual.
As far as I can ascertain my Epson driver has a maximum resolution of 720ppi thus leading to the Logical (I hope) conclusion, that the printer prints multiple dots to complete one pixel.
And to thinks we started with a simple original post about final image size!