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Wrong aperture assembly for Zeiss 35-100mm Sonnar

edmond

Member
My AE version f3.5/100mm seems to have a wrong aperture assembly.

3.5/100mm and f2.8/85mm Sonnar both have an incident light stopper ring in front of the rear lens group element. For my f2.8/85mm, when wide open at f2.8 and looking through from the front, you can see the aperture blades already at slightly closed down position more or less equal to the size of the back stopper ring. Looking through from the back of the 2.8/85, you would not see the aperture blades (or only a very little) at wide open position.

But for the 3.5/100mm, when wide open at f3.5, the aperture blades are recessed completely into the barrel. When stopped down from f3.5 to f4.0, the aperture blades then slightly closed down more or less equal to the size of the back stopper ring. Stopped down metering indicates that both f3.5 and f4.0 setting would get the same shutter speed reading. The shutter speed would only start to decrease from f4.0 and onwards. Compared with my f2.8/85mm, it seems that the assembly for f3.5/100mm ignored the adjustment to cater for the presence of an additional back stopper ring.

Is this aperture assembly applied to other 3.5/100mm lenses. Looking forward to receiving other users¡¦ advice.
 
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