To get the best picture, one needs more than a high-quality webcam. Lighting is important.
A bad webcam with great lighting is better than a great webcam with bad lighting.
TL;DR
- Two light sources.
- Positioned behind the camera, to the left and right.
- As far back as possible, at about 45 degrees, pointed right at the subject.
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As bright as possible, but "softened", using a good light bulb, a light box, a filter, or reflecting.
Two desk lamps and your ceiling light is a basic start. Those and another two lamps pointed at the wall behind the camera would be a great start.