Any optical system to be simulated in Zemax requires user input for the aperture. The “aperture type“ is specified via the general dialog box.
There exists many ways to specify this:
1. F/#
2. Entrance Pupil
3. Stop diameter
4. Numerical aperture
etc..
This video attempts to discuss each of these and guide the user for what is appropriate in their optical system.
Homework identical to Zemax #1 and can be found at