David H. Hartman , Feb 26, 2004; 02:29 a.m.
Your camera has exposure compensation of -2 EV to + 2 EV. This is covered on page 64 of the F55 manual. Unfortunately the compensation is only in steps of 1/2 stop. I dont own the F55 or N55. I downloaded a manual from Nikon UK. You can use exposure compensation to achieve similar results to changing the film speed. The only real difference is ISO speeds are in 1/3 stops.
If you want to change your film speed in the conventional way youd need to buy an N80 or better or a "classic" Nikon. If its worth the trouble I understand there are DX code stickers.
Hope this helps,