what kind of camera?
mine took a couple of go's but got there in the end
1. Set auto exposure on (default) and exposure value to 0 (or a little higher).
2. Place a bright light source, like a lamp, in the field of view of the camera so that it reaches 30fps.
3. Disable auto exposure with one of the enable button apps.
4. Switch the light off, the camera should still be producing 30fps and will continue to do so while the exposure settings are not changed.