remote shutter or delayed shutter will do much better job. I did not use these, therefore higher speed is necessary to get a clearer image. Theoretically, the speed for a 500 mm focal length should be greater than 1/500s to prevent from blurriness.

I don't know what is the difference in ISO between film and CCD or COMS. Now Sony, Canon and Nikon have full frame sensor (35mm) that will give a ISO greater than 1600 without obvious noise. But it was very very expensive.

I am using OLYMPUS system. They have a fixed size CCD (4/3 stander). So there is less temptation to burn the money.