[Leica] Always use a control

[Mike Johnston <michaeljohnston@ameritech.net>]

Speaking from long experience--I do edit the world's leading darkroom
magazine, so, although not a leading expert myself, I do hang around
with experts a lot--I would add that it's a very good idea to do a
control whenever you are experimenting with any of the more arcane
development techniques, such as water-bath, split or pseudo-split,
modified formulas, forced physical development, post-fixation
retreatment, Beutler formulas, et cet., et cet.

Oftentimes, photographers experiment with some one-off technique and
enthusiastically report successful results; but when doing the same
experiment with a control they are somewhat less enthusiastic, since
they often can't distinguish the specially treated negative from the
control.

- --Mike