Some usefull setting for the module you can also use sysfs kernel 2.6.x like this:
echo "4" > /sys/module/spca5xx/gamma
echo "217" > /sys/module/spca5xx/GRed
should set the gamma parameters to 4 and GRed to 217
The Gimp is usefull to get the good value :)
you need to close and reopen the device to get the change active.
otherwhise load the module for example with :

modprobe spca5xx GRed=217 GBlue=300 GGreen=224 gamma=4 
or
modprobe spca5xx OffRed=16 OffGreen=-32 OffBlue=-16 GBlue=288 GGreen=288 
