Connectix QuickCam (important tip)

Tim_Dorcey@cornell.edu
Wed, 4 Jan 1995 11:40:40 -0500


I believe this has been mentioned on the list before, but it deserves
re-emphasis. Unlike most cameras, the Connectix QuickCam does not have an
"auto-iris," (i.e., the ability to automatically adjust to available
light). Although there are certain advantages to this, a problem results
with flourescent light fixtures, which apparently cycle in the amount of
light they give off, producing oscillations in the brightness of the
displayed video image. Aside from the annoyance of the oscillations, this
behavior defeats the compression algorithm by causing the entire image to
change with each frame (in the worst case), so frame rates drop
dramatically. I just saw this in action, dropping what should have been 10
fps or so down to 1 fps. The only solution I can think of if you are in
this situation is to smooth out the flourescent cycle with some other light
source. Even if you add in the price of incadescent bulb and lamp, the
Connectix is still a good deal. Note also that auto-irises are not without
problems, as slight changes in the subject matter can change the amount of
light reaching the lens, causing it to open or close, and introducing
spurious changes in parts of the image that have not changed at all.

-Tim
__________________________________________________________________
Tim Dorcey T.Dorcey@cornell.edu
Sr. Programmer/Analyst (607) 255-5715
Advanced Technologies & Planning
CIT Network Resources
Cornell University
Ithaca, NY 14850
__________________________________________________________________