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Randy,
The blades uncover the whole (set) aperture faster when the diaphragm is set to a small aperture so
effectively the shutter delivers a longer exposure time (vs. the one it is assumed it is delivering). Because
the blades reach fully open position faster from the "midpoint" to the peak one would expect a bit of
underexposure when the lens is set to a large aperture.
Another way of saying this: if the diaphragm is set to f/22 the amount of light that f/22 allows to pass
is available for a longer time than that which is allowed to pass when the diaphragm is set to f/4 for example.
And the full amount that f/2 for example passes is available for a shorter time than that which f/4 passes.
But the discrepancy at the high end tends to be a bit less "problematic" than at the low end where an error
of maybe 1/2 stop or more can be experienced.
Anyone care to elucidate us further?
Andy
On Apr 1, 2014, at 11:40 PM, Randy Little wrote:
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