Back to main - gPhoto Slimshot Driver - What's Happening


Added support for Logitech pocket digital into CVS at sourceforge. It's been a while since the last update, due to new job etc. Anyway - Matthias Scherrer provided some very useful USB dumps, so some progress made on the above - it turns out it uses a different packet size, and protocol (ok, it's pretty much... different) from the ultrapocket clones, but not different enough that it merits a seperate driver.

An interesting note is that it returns (AFAICT) the same data for a 1024x768 image as for a 640x480 - I know they say software assisted, but, cmon guys! I mean....


All the interesting (read published ;) algorithms for interpolation seem to be patented. It's a hard world. Been working on one which uses a different approach to anything I've seen published, but of course the results aren't perfect as I have to shy away from some obvious (and therefore patented) stuff. Bah. Americans.

One thing which has been bugging me are some interpolation artifacts I've been seeing, but (in retrospect a bit obvious *sigh*) these seem to be the camera's fault. Green pixels on red and blue lines appear to respond slightly differently, hence I get striping in my images. I suspect this is due to a charge leakage.

Examples, (green pixels only) using Kurt Garloff's demosaicing algorithm (dem), mine (lee), and the original pixels uninterpolated (original). Striping is quite visible


Found a paper which gives several algorithms for better interpolation of Bayer demosaicing than bog standard bilinear. I think a constant-hue goal interpolation produces the best results given the low resolution of the camera.

Some closeups

Bilinear interpolation
(what the standard gphoto bayer function uses)
Gradient based interpolation
Windows Result
(Still a long way to go, though I've not modified the levels yet)


Found an interesting (though not much use to me! ;) teardown report on the camera.

Lee Benfield - 2003

Just interested..