[Leica] Light leak in M6?

["Doug Richardson" <doug@meditor.demon.co.uk>]

pieter@world.std.com (Pieter Bras) seems to have the answer to my M6
problem, and I'm most grateful to him for replying.

I'm afraid I hadn't R'd the FM 'cos second-hand cameras rarely have
the FM included.

A number of the affected frames do correspond to lens changes - not
sure about all of them through. However some lens changes carried out
outdoors did not create problems.

Most changes were done outdoors, and I was trying to work in my own
shade when changing lenses. However the Paris Air Show is a bit of an
endurance test (exhaustion test!) for a technical journalist, so it's
possible I got careless. I've always regarded shading the body as I
change lenses as a "nice-to-do" but not mandatory, arguing that the
shutter is either light-tight or it isn't.

Also why shade the hole in the body when you're about to cover it with
a great hunk of glass which is going to let lots of light stream in
for hours on end? Let's suppose that having no lens in place admits
100 times the light that a fast lens does. If five seconds exposure
with no lens in place is enough to fog the film, then why does 100 x 5
seconds with a fast lens uncapped not produce the same fogging? The
only hypothesis I can come up with is that an open mount admits the
light at a far wider range of angles than a lens does, and that some
if this light arriving at odd angles is sufficiently scattered from
surface to surface within the camera that it eventually works its way
to the film. But given that the camera can be carried outdoors for all
day with the lens cap off, why doesn't enough of the light arriving
through the lens follow the same route (perhaps after a few extra
scattering operations to get it started) and eventually fog the film?

Curiously I never had any problems in almost 20 years of changing
lenses on a IIIg, M2, and 'flex, and I'd always assumed that all have
basically the same general configuration of shutter.

Regards,

Doug Richardson