[Leica] Two sets of aperture blades?

[henningw at archiphoto.com (Henning Wulff)]

At 12:55 PM -0500 5/4/04, Karen Nakamura wrote:
>OK, am I on drugs or does Leica use two sets of aperture blades? It 
>seems on many of my lenses, that looking from the front, there is 
>one set (main set?) that closes down, but from the rear, there's 
>another set that gradually closes down and catches up at f/22 or so. 
>It's very odd.
>
>Is this to smooth out bokeh? Or am I seeing an illusion?
>
>Karen

Hardly any lens made by whoever has two actual sets of aperture 
blades. What sometimes looks like two sets is only one set, but the 
blades are cut so that in operation they look like two sets and in a 
way function like two sets so that structurally they support each 
other like two sets, so that when they achieve very small apertures 
they don't collapse through gravity or shock or form extremely 
irregular openings.

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    *            Henning J. Wulff
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