Le jeudi 04 septembre 2008 ? 03:17 +0200, Arne a ?crit : > > Concerning the vertical lines at 4800/2400 dpi for MP810, I'm wondering > > whether: > > > > - this is a normal behavior of the scanner (which would mean that it has > > to be compensated by the backend), > > - or if it's an alignment problem of the sensor, the lines corresponding > > each one to a particular sensor cell, but only at high dpi, the sensor > > uses all its cells to scan. > > > > I think it may be interesting that other MP810 users could give feedack > > on the current CVS backend, if possible, that's why I copy also the > > sane-devel list > > Yes I hope we get some feedback, as there was at least one other MP810 > user asking for the drivers. > I think it's normal behaviour, but if not, I need to know before the > warranty runs out! > > > Do you know if there's an alignment procedure for MP810 ? This is > > usually the case when you get a new scanning device. > > There is a printer-head alignment procedure but nothing for the scanner. > > > Have you the possibility to test the Canon Windows driver, and see if it > > behaves the same ? > > I borrowed a WinXP laptop and installed the latest drivers downloaded from > Canon Europe and found that they only support up tp 1200dpi. > If I was a Windows user I would feel very cheated by Canon about this as > they advertise 4800x4800dpi optical on the tech specs! > In fact I might send a message to Canon support about this and see what > they say. Same situation for more recent models like MP610, MP970, ... Canon drivers offer only up to 600 dpi or 1200 dpi, far less than the 4800 dpi advertised ! Never tried to contact Canon about that, but should be worth doing it. AFAIK, only Sane pixma backend can currently drive those PIXMAs at such high dpi, not Canon's drivers.
> > > Last point concerning the white lines at the bottom: this is simply due > > to the color planes shifting, as the backend algorithm to shift the > > color planes uses only that portion of the image that will contain data > > for the 3 colors. The bottom of the scanned image contains 2 and 1 color > > zones only, due to the color shift. > > So this is a little limitation for pixma CCD sensors, you must select a > > scan zone a little bit bigger at the bottom, then remove the image > > bottom white zone, that is padded on purpose by the backend to keep the > > image size the frontend expects. > > ok I understand, it's not great but I guess there is nothing that can be > done about it. Following Allan's suggest, should be easy to implement, I'll propose you soon a newer pixma_mp150.c file which should solve this issue, I'll keep you posted. Nicolas
