So I recently bought a Canon Rebel XS (refurbished directly from Canon). Here's the issue. When I try to take pictures at fast shutter speeds, they turn out way dark. I think my room is pretty lowly light, but I don't think it's that bad. But with the flash, it's perfectly fine. Only problem is, flash only works up to 1/200 sec. Any clues as to why this is happening and how I can get brighter pictures?