An 80 mm focal length thin lens is used to image an object with a magnification of -1/2.
The lens diameter is 25 mm and a stop of diameter 20 mm is located 40 mm in front of the lens.
How big is the unvignetted field of view [in terms of object size (in mm) and in terms of half field angle]?
How big is the fully vignetted field of view?
Magnification = l'/l (coupling this with the focal length, we can find the object and image distances)
Vignetting equations attached
The Attempt at a Solution
I've drawn a picture and looked at http://spie.org/x32310.xml. I found that l' = -240 mm and l = 120 mm. I'm not sure where to go from here. Thanks in advance for help!