Logitech Quickcam 2/SPCA5XX webcams look awful on Linux
Having been stung in the past and accidentally bought TWO of these bloody things (they're cheap) by accident, I spent a fair amount of time trying to get some semblance of a reasonable image off them.
robin@workstation:~$ lsusb Bus 004 Device 002: ID 046d:0928 Logitech, Inc. Quickcam Express
Of course, I'm not going to go through installation of the spca5xx Linux kernel module you'll need (you can find that on this website) - most distributions have a binary kernel package (or the source in Debian) anyway so do a quick search of your package tree for spca5xx before downloading the source.
These cameras seem to be incredibly sensitive to light - to the point that images blow out with a reasonable amount and underexpose when you're a mere whisker away from reasonable light.
After much fighting, I found the problem. When modprobing the spca5xx module, you should pass the parameter "compress=1" - it's hardly documented in the driver, but it's this that causes ALL the problems (over/underexposure and terrible performance). After doing that, you'll find ok quality images and a good 30fps with xawtv, etc. Obviously, it's telling the camera to compress the image data on the way out (why it doesn't do this by default is a mystery to me).
They might as well have called that driver parameter damnwellwork=1
So, when loading the driver do:
modprobe spca5xx compress=1
for some happier Linux webcammery.