Tom if you go to the calculator and select the 35 mm camera option and use that then ignore the width of the film and only use the height that will give you the width using a 300D. (did you follow that
) The hight of a standard 35 mm film frame is the same width as a 300D chip. ie 22.7 mm
PS the ccd calculator will give it in arcmin <=> divide by 60
