A photographic film camera adapted to receive a film cassette having a rotatable radial bar code data disk mounted at one end thereof is provided with a variable gain opto-sensor circuit responsive to the radial bar code for generating a sensor output signal having transitions through a logic threshold...http://www.google.com.au/patents/US5825008?utm_source=gb-gplus-sharePatent US5825008 - Apparatus and method for setting radial bar code disc sensor gain in a phtographic camera 
