how does camera know when to work in grayscale mode?

[orangefish 0]

Hello,

 

I am trying out a bullet day/night camera (as I mentioned in my other posts).

 

What I am trying is to block the photo sensor to force camera to work in night mode (with IR LEDs on). In this mode, if the surroundings are lit brightly, the camera shows a color image. However, if the surroundings are dark, the camera shows grayscale image. BTW, the camera does not appear to have a mechanical IR cut filter.

 

So my questions is, while the photo sensor is covered and the camera is thinking it is night, how does it decide when to show a color image and when to show grayscale?

 

I am thinking it might be programmed in the camera's firmware and the decision is made based on the illumination perceived by the CCD sensor.

 

Thanks in advance.

Regards.

[CameraGimp 0]

Hi,

 

I can't be 100% sure but I would guess that the camera uses chroma suppression triggered by AGC gain to go from colour to monochrome. From what you have said and tried out it seems to fit. So although your camera has a photocell, it only uses this to turn on the ir leds, it doesn't use it to switch the colour off.

 

Most colour cameras slightly reduce the colour strength at low light (it gives a cleaner picture) and if I had to make a choice I would say that is how your camera goes to monochrome. It probably suppresses chroma totally.

 

Some cameras suppress based on how much agc gain it is applying. The logic being if I'm applying 0db of gain it is bright, 10db it is getting darker, 20db darker still, etc. The settings in the camera firmware would be at this agc level start suppressing by this much.

 

I don't know how to suggest you test this. You might be able to try turning AGC off. If your camera supports this you might stop the camera going into monochrome completely. Not much help if you want to force the camera into monochrome though.