odd progressive brightness issues with Motion and USB webcam

[permitivity]

Hello,
I'm using the "Motion" program with a USB webcam. This webcam is an HD webcam with manual focus. When I use the webcam on a windows PC, it's fine. Nothing to note. When I first plug it into a Pogoplug running Motion and quickly look at the mjpeg stream, the image looks good. Then as I watch, the image gets progressively brighter and brighter, as if it's running some auto-brightness algorithm. The /etc/motion/motion.conf file has auto-brightness "off" and brightness set to "0".

If I watch it until the brightness is all the way up, and then I stop motion, and restart motion, the image STARTS at the high brightness appearance. However, if I unplug the webcam and plug it back in and restart motion, the image starts out fine again (normal brightness) then starts to do the progressive brightness until it's all washed out like in the image below.

http://s11.postimg.org/41kq56vjn/odd_mo ... htness.jpg


So, here's 3 images the screen. From first to last is about 40 seconds. I've looked through the motion config file and couldn't figure out what I'm missing.

I've tried another usb webcam on the pogoplug, this time a nicer Logitech C920, and it's fine. No weird brightness issue. Any suggestions on why this webcam is doing it? It's a cheap USB webcam,b ut still it shouldn't be doing this, right?

[Geoff]

I have a very cheap webcam (Logitech QuickCam Messanger [sic]), and it works ok with auto-brightness on and brightness 96. It also works with auto-brightness off and brightness 0. I suppose there's no harm in trying it with auto-brightness on.