A resolution-select arrangement is provided for a fiber optic document scanner (or scope) having its exit field coupled to an array of discrete sensors. An initialization procedure provides an address string which associates at least one address of the sensor array with each of many of the positions of a light beam incremented along the axis of the entrance field. Subsets of the longest address string are derived and stored separately in consecutive ROM addresses starting at a corresponding start address. Resolution selection, conveniently under software control, selects the starting address corresponding to the desired resolution and increments through consecutive addresses of ROM where the associated address string is stored.