Mechanical Backfocus distances:

(1)  From CCD to rim of camera body [-A-], excluding front plate = .492 inches (12.5mm)

(2)  From CCD to exterior surface of the camera front plate, excluding D block = .742 inches (18.8mm) *

(3)  When D-block is attached to front plate, add .270 inches = 1.012 inches (25.7mm) for new cameras, or
      .962 inches for older cameras.

(4)  With CFW10 attached to camera replacing front plate = 1.32" (33.5mm) for new and older cameras.

(5)  With CFW10-SA attached to camera's front plate = 1.54" (39.1mm) for new cameras, or 1.49" (37.8mm)
      for older cameras

(6)  With CFW8A attached to camera's front plate = 1.74" (44.2mm) for new cameras, or 1.69" (42.9mm)  for
     older cameras

The normal configuration of the camera as shipped from the factory is (3) with D-block attached to the front
plate of the camera.  The front plate is the 5" round plate containing the 1" round optical window over the CCD.

*  The front plate is .250" thick on the most recent models of ST cameras.  On earlier camera models it was
.200" thick.  It is easy to tell which version you have by measuring this from the outside of the camera.  If you
have an older camera then the distance from the CCD to the exterior of the face plate will be .692" (17.6mm)
and the distance to the exterior surface of the D block is .962 inches (24.4mm).

Some example configurations are shown in the diagram below: