iMac 2020 bootcamp Windows 10 camera black

Hi, 

I suggest you not using bootcamp maybe your windows can't detect your mac camera, if you really need windows then using parallel desktop maybe easier to share hardware like webcam to use both mac & windows. 

hope it helps.

I am also facing the same problem with Bootcamp model iMac 1,1 and iMac model 20,1 camera showing black and freezing. 

But the windows 10 camera application working fine without any issue.

Is there any solution to fix the problem

I've noticed this as well. I did manage briefly (gutted the drivers, downloaded relevant support files for my iMac Model and forced them to be used) to rectify this earlier this year, but as the incrimental 21H2 updates kept rolling out, the resolve went away. Rather  than spending any more cycles on this, I will be buying a good Camera/Mic clip on with actual drivers for Win 10/11, rather than shoe-horning back the 2006 Microsoft USB HD Video drivers.

 Go to Settings > Video > Advanced and change 'Video Capturing Method' to 'Media Foundation.'