Not too late to offer some additional thoughts on this topic, I hope. Following the suggestions of some of the more knowledgeable folk on the list I did some experiments.
The first was to gain an idea of the native resolution of the ESC 1160 printer. I used a scan of the PIMA/ISO digital camera resolution chart and printed it at a size to allow the printer resolution in lp/mm to be read off directly. I achieved 6-7 lp/mm with the printer set to 720x1140 resolution, with larger figure for the long axis of the paper. This result is close to 180 lp/inch and about the limit of vision of the unaided human eye. I also rasterised a postscipt file of the ubiquitous USAF 1951 lens test chart. Again I obtained the same figure for the maximum resolution of the printer. I rasterised the file to 1440, 720, 360, 240, 180 & 300 dpi to see the effect of file size on the print quality of these geometrical shapes. I could discern no difference in quality between the 1440 and 720 dpi, but thereafter there were discernible (with the aid of a loupe) differences. I could detect no loss in quality when setting the printer to 720 x 720 dpi as opposed to 720 x 1140. These figures suggest to me that we do need high resolution for line art images, but what about standard photographic images? I took a number of images at random from my database, some were scans and some digital camera images. I printed a small section of each by resizing, but not resampling, to 180 dpi. I also resampled these images to the same size at 360 dpi using S-Spline, which has given as good if not better results than other interpolation techniques I have used. With these photographic images I cannot find really obvious improvement of the 360 dpi images over 180, except that in some images at the higher resolution oblique lines are slighly smoother when viewed with a loupe. One caveat, I did not sharpen any of these images. Although I accept that sensitive sharpening is an important aspect of printing, I just did not want to introduce additional variables. I can see now why there is such a diversity of opinion and practice when it comes to resizing images, and also why some folk are perfectly happy to let the printer driver sort it out. Tim Mimpriss =============================================================== GO TO http://www.prodig.org for ~ GUIDELINES ~ un/SUBSCRIBING ~ ITEMS for SALE
