I have been messing about with a Canonet for a while now, and have noticed a tendency towards over-expose at 1/500 and f16. What escaped me was that it was only in circumstances demanding these two parameters that I was getting over-exposure. Under all other situations demanding 1/500, the exposure was perfect (thus 1/500 is not slow).

This morning I was re-reading my copy of the 'Kodak Professional Photo Guide' and I noticed a blurb about compensating for leaf-shutter geometry at high speeds. The blurb stated that at small apertures and high shutter speeds, one must always compensate by up to one full stop. Apparently, this is an inherent weakness of leaf shutters.

This strikes me as being a bit strange...Can someone explain to me why this happens? Why is this not a problem with focal-plane shutters?