Archived posting to the Leica Users Group, 2002/07/15
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]> Darrell, > > Excellent info from Henning, Tina, et al. Thanks! Scan dpi is not > the same > as print dpi. Technically (as I have designed a number of scanners and know a bit about this subject), scanners scan at SAMPLES per inch, and output data that are PIXELS (and there is really NO per inch information for pixels, as pixels have no inherent dimensional values. Only when inputting and outputting do the "per inch" really matter. The files do contain dimensional info, but this info isn't really meaningful, as far as the digital image is concerned, and is more for reference). Printers print (inkjet that is) at DOTS per inch. The printer driver translates the pixels into solid ink color dots to simulate tones. I STRONGLY urge scanning at the full optical resolution of the scanner, and when printing, simply re-size the image (with OUT interpolating. Uncheck one of the boxes in the PS resize image window to disable interpolation) and let the pixels per inch to the printer driver fall where it may. This is providing you have sufficient PPI to the printer for your image size...and for very large output, 180+ is fine, and for smaller output size, 240+ is fine...more is better up to a point (meaning will yield better output, but still, you're better not interpolating the data and sending more data to the printer driver than interpolating and degrading the data), but you've got what you've got from your scanner. These minimum recommended numbers are very image dependant. There is no magic pixels per inch for the current Epson inkjet printers... If you resize the image, and do interpolate the data, you degrade it. > I've been using 360 l/mm as an even fraction of the printer's 1440 res, There is no reason to use an even divisor, as the dither patterns of typical inkjet printers do not care. You are better off NOT interpolating the data (except when the "need" for GF arises, of course, as stated above for large output sizes where your PPI to the printer falls too low) and simply sending the printer driver as much as you can. > ...and was just doing web display. For web output, of course, scanning at far less than the optical resolution of the scanner may work just fine...in fact, some scanners may do a very decent job if you 1/2 or 1/4 the optical resolution...but the bottom line is experimentation will give you your own answers. Regards, Austin - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html