Flicker in QuickCam? Whose fault?

Michael Sattler (msattler@jungle.com)
Wed, 22 Feb 1995 17:10:08 -0800


ko@komac.knoware.nl (Ko Stoel) said:
>
>CU-SeeMe, QuickPict, QuickMovie all suffer from QuickCam not being accurate
>at it's exposure time. Every once in a row frames differ in brightness.

Connectix responds:

European countries do not tend to use incandescent lamps like we use here. They
use flourescent and halogen and a variant of incandescent, all of which pulse.
Moreover, the European power frequency is 50Hz, not 60Hz, which means that
flicker from light sources tends to drop down into the 1/100th of a second
level, which is about what QuickCam is set at for normal lighting conditions.

What this means is that QuickCam will get perfectly fine pictures until its
integration frequency happens to coincide with a light pulse, which will result
in a darker frame. The human eye cannot see this problem.

Second possibility is flicker from monitor reflection (it doesn't take much,
and most multisync monitors are updating at about 75Hz--I don't know what it is
in Europe--which is equivalent to a dimmer room integration time).

Flicker in image is almost never caused by QuickCam componentry, almost always
by lighting. He should try adding lighting or subtracting lighting to change
the integration time on the camera. He should try blocking the light from the
monitor temporarily. This should change the symptoms or make them go away
completely.

And yes, we tried to answer him. I got a bounceback twice.