Just noticed this sentence on p.46 of the E-P2 manual: "ISO 200, which gives optimal noise and gradation balance, is recommended for normal use." Also: "For a slower shutter speed or when you want to open the aperture, use ISO 100." As I read this, the native ISO value for the chip is 200, and 100 is - in effect - a built in ND filter. From the old film days (Kodachrome 25 is better than 64 is better than Ektachrome 200, etc.) I've had the habit of using the lowest ISO I can get away with. As a result, I've been shooting at 100 preferentially. I guess 200 is the best default.