The Fed-4 were produced in two versions. The first model (reffered to as Fed-4 (a)) has wind knob and was modified from Fed-3 (a) to accept a light meter. The Fed-4 (b) has much higher viewfinder assembly to add a light meter. The light meter control knob is where the rewind knob was so the rewind knob now sticks out of the side. The Fed-4 (b) camera again was available with either single or dual lettering .