Desaturated video

The white board is the problem.  If you raise the exposure or gain setting so it will not appear gray, then the written lines will appear pale (or blead) and the presenter (you?) will appear over-exposed.  The problem will be worse if the scene is highly illuminated.  This is a dynamic range challenge that, really, no extant cameras can overcome.   One worse situation comes to mind: capture the surface features of a full moon and, at the same time, capture the light of stars in the nearby sky.  That can be faked, or achieved with special filters and masking, but not done with any camera alone.

Two alternatives:

1. A greenboard, preferably dry-ink erasable, or any non-white sheet of paper or erasable plastic you might place over the whiteboard.  This will reduce the extreme contrasts.  White, yellow, or bright red ink or chalk will be quite visible.
2. Create or edit all your presentation graphics or illustrations using computer software, save the files, or use screen capture (still or video).  Then insert the files  in your video.  They can either occupy the full screen or a portion of it.  If you use green screen, you can make it appear that the graphics are behind you. 

Most video presentations employ some variant of #2.   It gives you the most control over what you present, and also spares the viewers from the tedium of watching you write or draw things, ever so slowly.  The one thing bad about this approach is that many presentations flash the graphics too briefly for a viewer to understand or analyze.

Some old-school presenters write out their illustrations manually on a board or sheet of paper, but they must be very humorous, or have some other charm, to retain their viewers.  Sometimes their text or graphic content is prepared in advance, and their manual contribution is to draw highlight arrows, lines, or circles on the paper or screen.