Ok Stef I have a bit more time to concentrate on this at the minute. I have updated the white_shading.pnm and included it at http://sites.google.com/site/bez625/updates-1/update080310 there is also a copy of the latest scan there too. I only have 20 shading lines in the shading area because there is a lot of blue in that area. Should I widen it (more shading lines) or should those blue areas be included?
Also how do I disable the averaging? Is it a software thing or is it on one of the registers? I'm also not too sure what you mean about the offset, is it the DAC offset? Thanks Chris On 03/05/2010 07:26 PM, stef wrote: > Le jeudi 4 mars 2010 17:13:12 Chris Berry, vous avez ?crit : > >> On 03/03/2010 06:03 AM, stef wrote: >> > ... > >> Ok thanks guys, this seems to have done the trick! There is now a black >> line down one side of the page (not sure if that is supposed to be there >> or not) and the colours seem to be a bit grainy. I have attached photos >> to the site page >> (http://sites.google.com/site/bez625/updates-1/update040310), these show >> the shading calibration and the latest current scan. >> >> If possible could you take a look and advise on how to sort out the >> grainy parts of colour, im completely unsure myself :) >> >> Chris >> >> > Hello, > > I think there are a couple of things to look. First > compute_coefficient() > can't handle case where averaging is enabled for CCD, either disable averaging > it or improve the function. Then you'll have to find what the offset to feed > as a parameter. To find it I usually give 0 offset, then I count the number of > vertical lines between a dark line and a bright one. Because a dark line isn't > corrected and another is applied the correction which turns it bright. Then I > use this value as offset. With some trial and error you can have a good value. > You may also look at the color matrix. > > Regards, > Stef > > > -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.
