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Re: [OM] number of aperture blades

Subject: Re: [OM] number of aperture blades
From: Matthias Wilke <Matthias.K.Wilke@xxxxxxxxxxxxxxxxxx>
Date: Tue, 26 Jan 1999 10:23:56 +0200
Keith asked:

>>....If Olympus chooses to use more in certain lenses
>> there is probably a good technical reason for it.
>
>Could it just be that the physically small diaphragm assemblies have 5 or 6
>blades and the larger ones have correspondingly more in order to present a
>smoother contour to the shape of the aperture? I am not acquainted with all
>of the lenses on Steven Read's list but that was my impression.

The observation seems to be right, but probably has more to do with the
greater mechanical difficulty to supply a smaller diameter with 8 - 11
blades (the 24mm Shift lens as one of Olympus' gems has only 6 blades and a
small diameter of the aperture). But the shape should be independent from
the diameter.

Matthias



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