Why do leaf-shutters 'fail' at high speed?
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?
It makes perfect sense!!!
You lot really are incredible!!!
I was hoping to get at least one answer that I could understand. I got three!
Thanks very much, I understand now, and what is more, I can now make practical use of this knowledge.
So why leaf shutters, then?
Please permit me a follow-on question, then ;)
Why bother with leaf shutters then? Is it because 75 years ago, they were the only way to go? Is it because you can incorporate shutter and aperture elements in one small package?
Why are they still used (there must be some advantage, no?) If focal-plane shutters can move at faster speeds, why not simply use them?