Abstract: A photographic printer includes an automatic film measurement system which provides measurements of a film negative at defined discrete or continuous areas. The measurement system includes a light source on one side of the film, an array of light sensors on the opposite side of the film, and a plurality of interchangeable first light-guiding modules. The interchangeable modules are used with different size film and are interposed between the film and the array of light sensors. Each module has a plurality of light-conducting channels which have their first ends exposed at the first surface proximate the film and have their second ends exposed at a second surface proximate the array. The pattern at the second surface corresponds to the array of light sensors so that the light sensors receive light from different portions of the film through the light-conducting channels. In preferred embodiments, a plurality of interchangeable second light-guiding modules are also provided for use with different size films.