Recent content by grepnold

CorkyG, because this was and I believe still is the only discussion on the web of a problem that will affect all who require dimensionally accurate scans. It has resulted in a workable solution for me, and has suggested other ways to correct for this error that others may wish to try and to...

I recently bought a CIS scanner that doesn't have this problem, as a previous poster pointed out. CIS scanners use a sensor the width of the image and a linear trough-like mirror in place of a lens, so don't suffer from pincushion and barrel distortion. But in many other ways they're inferior...

I'm using ImageMagick API calls in my application so I can include correction if I need to. I'll be sure to let you know if I do. As a start, like you I'll just use the centre, and I'll align the longer dimension with the vertical axis, to minimise these errors.

Thanks Josh. I had no idea there were two sorts, and had always assumed a reducing lens and CCD setup. This http://www.imagemagick.org/Usage/distorts/#barrelinverse is the sort of transform that might give a useful approximation, though if you wanted to map the exact distortion as scanned that...

Hi Josh. My interest is mainly for a task that involves automatic synchronisation on a pattern, and I don't know yet whether the degree of distortion will be a problem for that. I was wondering whether it was just a problem with Epson Perfection models, as both the OP and myself found it with...

Here's an example of the distortion. I scanned a measuring tape horizontally and pasted a portion from the center against a portion from the edge. The top one is the edge and the bottom one the center. The 2 and the upside-down 6 line up, but 40mm to the left the 9 and the upside-down 9 are a...

Thanks for replies, This is a flatbed. The distortion is not so great that is obvious to the naked eye. I scanned a measuring tape horizontally and vertically. Superimposing the vertical image on itself displaced vertically shows no distortion - the grids line up. But copying an end segment...

Coming late to this discussion. I have a synchronization problem which I think is also due to this problem. The scanner builds up images by assembling scanned lines as it moves along the vertical direction. This is done using a stepper motor and I would not expect it to be the source of this...