Very minor but:
the insert menu for focal blur camera uses the following definition for
confidence:
confidence 0.95 // [0...1] when to move on while sampling
(smaller is less accurate)
which would imply that you could use 1
the docs state
...confidence ... can range from 0 to <1...If 1 is used POV-Ray will issue a
warning and then use the default instead.
-tgq
