Try setting the camera to ISO 50 and leave it there. In Auto ISO mode, the camera most likely increases the ISO to as high as 400 which will give u faster shutter speeds, but lots more noise.
You may need to use the flash in more situations though. Also keep in mind that even at ISO 50, with flash, in darker situations the images will have some noise in the shadow areas.
It's the price you pay for tiny sensors with huge pixel counts.
TOM...
Personally, I've never liked the Casio sensors.
