You can use manual lenses in manual mode on the F80/N80 (every other mode will give you an error) but metering will not work, not even in manual mode. Not sure if this is true for the D100 as well. Furthermore focussing is a bit tricky without any support from a focussing indicator or the like. I also doubt that TTL-flash metering will work with a MF-lenses but I never tried this so I'm not sure here. hope that helps Thomas