Every optical system has a system aperture specification, such as F/#, entrance pupil diameter, numerical aperture, or cone angle. This sets the width of the on-axis beam that the optical system will collect in object space. In ZEMAX, this data is specified in the Aperture tab of the General dialog. This can be accessed from the main menu via the menu option, "System > General" (or "Gen" button in the button bar).



 The Field Data dialog is used to specify the points on the object surface from which rays are launched. This dialog can be accessed from the "System > Fields" option in the main menu ("Fie" button in the button bar).

The wavelengths of rays that are traced are set in the Wavelength Data dialog. This dialog is accessed from the main menu option, "System > Wavelengths" ("Wav" button in the button bar).