Stitching with the Manual option selected under Document
stitching on Wizard step 2 (Choose stitching method) does not use the
focal length setting in the Wizard. It skips Wizard step 3 (Describe your
camera) because camera settings are not needed for document stitching.
This is correct behavior.
However, the next time you perform a photo stitch, the focal length
setting has been reset to 1000mm or sometimes even larger than 1000mm.
This is incorrect behavior. When the focal length is larger than
1000mm, The Panorama Factory displays the message
Please enter a number between 1 and 1000.
Unfortunately, if Automatically detect focal length is
set, it is not possible to change the focal length value. The error
message is displayed repeatedly if you attempt to turn off
Automatically detect focal length.