Electronic – Regulate brightness over video composite signal

brightnessvideo

I have a b/w camera that outputs a video composite signal. At night it works very well, but during the day it's so bright everything just turns white. Is it possible to add a potentiometer to be able to dim the brightness?

If so, what resistance value should I use and how should I connect it, in series with the video signal or a to-ground from video signal setup?

Best Answer

Your camera's sensor is probably saturating in daylight so attenuating the video signal would just mean that everything looks grey rather than white. The only cure is to use a lens fitted with an iris to reduce the amount of light entering the lens. Better still, fit an automatic iris lens which uses the video signal to adjust the iris aperture to keep the video level constant.

It is also possible to use neutral density optical filters to reduce the light which would be cheaper to retro-fit but difficult to make adjustable.

As an aside, a composite video signal contains timing information (sync pulses) in addition to video brightness information, so attenuating the composite video signal would also attenuate the sync pulses - which is not desirable.