Literally just discovered this little tip ten minutes ago when I was video chatting with my sister. The lights in the room were off since my wife was watching a movie on the couch about 20 feet away and it was extremely hard for my sister to see me. While minimizing some windows on my desktop I noticed windows with bright colors, especially white would make my screen brighter, which then put more light on my face for the camera to pick up.
I then decided to open a completely blank Safari window and maximized it across the screen. This extremely simple tip, helped tremendously for brightening up the image being sent to my sister.
If you want to try this out just open up any web browser and in the URL bar type in “about:blank” and hit enter.
See the difference below: