[Kenneth Taylor]

The D3100 does not allow you to control shutter or ISO in video mode, only the f stop. Only the D7000 and up allow you to have manual control over everything. You can change the shutter and ISO but it will only effect the still images. Also, to have your aperture changes take effect you have to exit live view, make the change, then return to live view. Again, changing the aperture in live view will only effect stills. What the camera does in regards to ISO and shutter is unpublished. My guess is the shutter is 1/50 and the ISO is auto. I worked for Nikon USA for a few years and Japan would not provide us with that information.