My Camera - Determining lens type for ICARUS

ICARUS Motion Tracking Software (2.09)
Below is a setting for the lens of common cameras. I am not sure which setting, if any, that I should use.

http://mysite.verizon.net/vze3nvj6/Blender/forum/icaruslens.jpg

My camera lens has the following information, printed on the actual lens attachment.

25x OPTICAL ZOOM/AF

JVC VIDEO LENS

F=2~55mm f1.8 Ø27

The ICARUS menu is asking for the “Aperture Height (mm)”. My best guess is the actual size of the opening (the f-stop) of the aperture. Therefore I would have to assume that “1.8” would be the correct choice. What is the “1.8”? Physically, I see that the aperture is approximately less than 1/4 inch. Myabe I should use 1/4 inch CCD? They are asking “mm”, yet many of the choices are in “inches”.

ALSO…
Does anyone know about the lens distortion settings in ICARUS?

Iarus is asking for the apeture height, but from the choices in the menu of the screen shot, it is obvious that they want the size of the image area on the film/sensor plane. In other words, the apeture height has to be at least as tall as the size of the recording meduim used, be it film or ccd.