1. A computer-implemented method of optical character recognition, comprising: receiving at a computer a plurality of proposed character assignments for at least one instance of a character in an image on which optical character recognition is being performed, each of the character assignments representing a character determined from a character set for the at least one instance of the character by the optical character recognition, the at least one instance of the character residing in one or more multi-character character strings, at least one of the multi-character character strings known to exclude a subset of at least one character from the character set based at least in part on the at least one multi-character string's location in the image; and eliminating at least one of the proposed character assignments by comparing the at least one of the proposed character assignments to the subset of at least one character excluded from the at least one multi-character character string.