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N 100mm f2.8 Makro-Sonnar PROBLEM??

 
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Piginho



Joined: 17 Oct 2010
Posts: 2

PostPosted: Sun Oct 17, 2010 10:39 pm    Post subject: N 100mm f2.8 Makro-Sonnar PROBLEM?? Reply with quote

Help please - anyone who has this lens (or has had in past and knows the answer). I have just purchased one on eek-bay! and all seems well except what I believe to be slightly strange behaviour from the diaphragm.

With the lens off of the camera and set to f2.8, I would not expect to be able to see the aperture blades at all. As they are stopped down electronically, powered by the camera, they should remain fully open when off camera (whatever aperture is set).

However, if the lens is focused at around 1-2 meters or closer, the aperture blades close up slightly, but quite noticeably.

Putting the lens on camera gives the same result and if you press depth of field preview they close down a little more. This is even the case if focused at infinity and the aperture is fully open, press DOF preview and the blades close slightly.

I'm not sure if this is just the way this lens is designed to work, or if it has a fault. If anyone who has this lens could have a look at their own lens and see if it does the same, I would be very grateful.

Regards
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conurus
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Joined: 15 Aug 2006
Posts: 795
Location: Vancouver, Canada

PostPosted: Mon Oct 18, 2010 6:19 pm    Post subject: Reply with quote

Hi Piginho,

What you describe is not a problem at all, but by design. Indeed, the N mount Makro-Sonnar 100/2.8 is equipped with two sets of aperture diaphragm. One of them is the normal aperture diaphragm which you control from the camera body and depth-of-field preview. The other aperture diaphragm is fully open at infinity and gradually closes down as you focus to 1:1. The function of the second aperture diaphragm is unknown. If you write to Carl Zeiss their technical support is outstanding even for discontinued products and they probably will be able to explain that to us. If you allow me to speculate the N Makro-Sonnar is an unorthodox design and is actually faster than f/2.8 at 1:1 so requires a second set of aperture diaphragm to compensate.

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I am a bird and I uncovered the E, EF and N-mount communication protocols!
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Piginho



Joined: 17 Oct 2010
Posts: 2

PostPosted: Mon Oct 18, 2010 11:03 pm    Post subject: Reply with quote

Thanks for your response. It has put my mind at rest and who knows, maybe someday it will find it's way to Canada along with my other 4 N lenses for conversion. Still trying to hang onto film for the moment, but the day will come....

Regards
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EHRphoto



Joined: 30 Dec 2008
Posts: 8

PostPosted: Mon Oct 25, 2010 2:41 pm    Post subject: Reply with quote

A Flare Cutter? Rolling Eyes
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Eddy Rahardja
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