lsisaxon said:800, you get underexposure by 1 stop.
200, you get overexposuer by 1 stop.
100, you get overexposure by 2 stops.
Setting the camera ISO just affects the metering on a film camera.
Ah...but i dare not try that cos i didn't what will happen to the results.
By the way just to OT a bit, i just bought a roll of velvia 100 to compliment the EF 100mm f/2.8 USM Macro i just borrowed for the weekend. Results should be stunning i suppose.