Which shutter are you using?
 

Pardon my ignorance as I am still trying to get used to the progressive shooting modes on my 200. I am doing a lot of live events and I was happy with the light sensitivity on my old SD cam. With the switch to HD I find that I need a lot more light. A lot more light.

However I do find that when I am shooting at 25p I can set the shutter to 25 as well giving me more light. Or so it seems Any downsides to doing this?

Svein Rune

The first disadvantage of slow shutter speeds is motion blur. High motion items will appear much more blurred with slower shutter speeds. Shutter is always a balance: slow causes blur, too fast and you get a strobe like effect. Try watching Olympic swimming where everything looks surreal and you can see each ball of water leave the pool in tack sharp detail.

If you are shooting seated interviews, 1/25th might work just fine for you. For pans and moving camera shots, it may not work particularly well. I prefer to use a shutter at twice my frame rate: for NTSC 30 fps, I "normally" use 1/60th.

Svein, the requirement of light in your camera depends on, among other things, the focal length that you use and the master black level. The Fujinon lenses supplied with the camera lose light very fast as you zoom in. If you find yourself "starving" for light you can try to minimize the distance between the camera and the subject, raise the master black a couple of point or use the black stretch or a combination of these methods. Using slow shutter is a cheap and better way, IMHO, to gain light than using gain, which would cause strong digital noise in your footage. The limitation is the motion blur. Eric Gulbransen posted recently an interesting list of frames at different shutter speeds, you can see by yourself what is the difference between shutter off and shutter at 90 and 180 degrees.
The standard used in motion pictures is to use a 180-degree shutter or, at 24fps, 1/48 of a second. If you use a 90-degree shutter, or 1/24th (1/25 in your case), you gain much more light. Nothing wrong with it but you have much less "wiggle room" with camera movements and it would be very challenging to do any handheld work.