How to adjust for auto-adjusting brightness
Have you added lights to your computer to brighten your face, only to find that your webcam auto-adjusts the brightness to bring your light right back down to where it was before?
SO ANNOYING!
And if you've tried to fix this on your own, you probably know already that there is no setting for this in Windows.
After a lot of poking around, I finally discovered a trick that will let you adjust your brightness anyway:
1) Close any apps that are currently using your webcam
2) Open Camera (click the Windows icon and start typing "camera")
3) On the left-hand side of the screen, in the middle, click the brightness icon:

...which will bring up a slider. Raise the brightness with the slider, then close Camera.
4) Now re-launch Zoom, and you'll find that the baseline brightness is set to where you adjusted it in Camera!
Why does this work? I have no idea. But it does!
(If you're a Mac user, the instructions here look promising.)
Enjoy!