On Wed, Jun 18, 2008 at 9:25 PM, Richard Reynolds <[EMAIL PROTECTED]> wrote:
> OR for one specific printer FEEL free to correct me if I am wrong on the > math > > lets assume were using a standard print size of 17*19 (ignoring itll do > lengths up to some 20 feet) > it prints nicely at 4800*1200 but because IM not sure how it gets to the > 4800 lets just use 1200x1200 > has 8 colors > assuming it uses 8 bits per pixel per color (Id say thats a safe bet) but > might be a tad high > itll use only 11.5 Mb per square inch > and in that 17x19 it only requires 2.8gb of ram > We are discussing two fundamentally different types of printer. A laser printer forms a complete page image on its electrostatic drum, and then rolls that image onto the paper. This process can not be interrupted. Thus the laser printer needs sufficient memory to hold one page image, possibly with compression. A color laser printer is composed of several print engines in series, all of which must have formed their images before the paper starts to roll. An inkjet printer prints the image as a series of raster scans. Each scan is independent of previous scans, and there can be a moderately arbitrary wait time between scans. For best results, one wants to minimize this wait time. Reading the specifications of a moderately high-end inkjet printer (HP T610) <http://preview.tinyurl.com/2f4w2m> I reach the following conclusions. The print head contains 176 nozzles for each of 6 colors. At 1200 dpi, this makes a raster swath of 0.15 inches. There is only one inkdrop size for each nozzle, so this means one bit per color per pixel. At a page width of 44 inches this takes (176 x 6 x 44 x 1200) = 55.6 megabits per swath. The printer comes stock with 128 megabytes of memory, which means that (128 x 8 / 5.6) = 18 scans can be buffered ahead. Another interesting fact gleaned from the data sheet: Print speed is 110 square feet per hour. 110 ft^2/hr * 144 in^2/ft^2 / 44 in / 3600 sec/hr = 0.1 in/sec paper advance rate. This means that the scanning print head completes one round trip in (0.15 in / 0.1 in/sec) = 1.5 sec. It was my observation at one time that the print head moves across the paper in one direction laying down the ink, and then retraces at a higher speed while the paper is advancing. Sort of like an ASR33 teletype. carl -- carl lowenstein marine physical lab u.c. san diego [EMAIL PROTECTED] -- [email protected] http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-list
