ABSTRACT
A condensing lens transfers energy from the light source to the entrance pupil of the projection lens. It must also provide uniform illumination at the film (or other object that is to be illuminated). The assumption, of a circular uniformly illuminated pupil, is imbedded in the usual illumination formulas given in texts (Smith 2000:241). The illuminance produced at the image, E, is given by E = T π B 4 [ f # ( m + 1 ) ] 2 , https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315222295/bd2ad0d9-a48e-40ac-8986-c51474069cbd/content/eq131.tif"/>
