Archived posting to the Leica Users Group, 1999/08/19
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Repost as requested. - ----- Original Message ----- From: Erwin Puts <imxputs@knoware.nl> To: <leica-users@mejac.palo-alto.ca.us> Sent: Monday, August 09, 1999 5:58 PM Subject: [Leica] Erwin's adventures in digiland. part 2 Print fumdamentals. The ubiquitous inkjet printer generates a color by splashing small droplets on a location on the paper. These droplets can be next to each other or they can overlap. The smallness of any individual droplet is not a measure of resolution or sharpness impression. It merely tells you how smooth the colorblends may be on the paper. As the typical inkjet printer has 6 colors only a limited range of colors and colorshades can be produced. All other colors and shades demand the use of a halftone or raster technique. If the printer would use a 2x2 matrix 5 additional shades can be produced. If we need the full range of shades a 16x16 matrix will b used. But such a raster needs space. It is quite simple. The larger the raster area the more shades can be faithfully reproduced. But the larger the area of such a matrix the greater the loss of resolution or lines/inch. This is analogous to the discussion 35mm print or medium format print. The latter can give a much smoother image (at the same area of print enlargement) because it has more silver per unit area for tonal recording. If we print at a 1440 dpi, we get a very smooth image, but not necessarily a high resolution (or even more relevant: a high micro contrast). Photo-quality printers use at least a 2x2 raster-cell to reproduce the tonality of colors, so the 1440 should reduce to 720 or even 300 dpi in print. And rasterisation will always show when looked at close enough. So with an image-resolution of 150 to 300 pixels per inch we reach the threshold of current highquality inkjet printers. To get better images on print a fully digital printer is needed. That is yet another story. As an aside: a 1800 x 1200 pixel image has a total of 2.1 million pixels. There is no direct relation between a image pixel and a print dot. So a 1440 x 720 dpi print area ( 1 million dots) does not relate to the 2.1 million pixels in a 1:2 relation. The 2x2 matrix cell will intervene. What about the 2700 x2700 negative scan. The 7 million pixels here will be forced into the same 1 million dots (plus rasterization). So for the inkjet print is it overkill. Next installment: a real comparison Erwin