A working FMOS requires both an Upper Tube and a Lower Module. Looking at the FMOS System Diagram, there is a selection of Upper Tubes (Standard or Mini), in a variety of focal lengths from 60 to 500mm. There is also a selection of Lower Modules from simple optics to coaxial illumination with internal focus and again they come in a variety of working distances from 30 to 190mm.      

The FMOS Specification Charts detail the optical properties of different combinations of Upper Tubes and Lower Modules when  used with oblique/substage or coaxial illumination. Performance for use with Optem Long-Working Distance Objectives is also provided.

Properties included are working distance (wd), numerical aperture (NA), resolution (Res), magnification at the camera sensor (Mag), depth-of-field (DOF) and field-of-view (FOV) as measured in millimeters for camera formats from 1/4" to 1".

You will note that as the working distance increases, so too does depth-of-field and field-of-view. Inversely, as the above factors increase, N.A. (resolution) and magnification decrease.  NOTE: The chart also indicates those areas where a Coaxial Illuminator Lower Module will not provide a fully illuminated field.