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[OM] Re: Nikon DX 18-200/3.5-5.6G on film

Subject: [OM] Re: Nikon DX 18-200/3.5-5.6G on film
From: Moose <olymoose@xxxxxxxxx>
Date: Thu, 17 Apr 2008 15:23:51 -0700
Chuck Norcutt wrote:
> I agree with your reasoning regarding the mirror but I would have 
> expected a solenoid actuation in an electronic camera.  And, regardless 
> of how it's implemented Nikon and Pentax were both able to do it.
>   
I don't know about Pentax, other than the screw mount ones with the push 
pin. The Nikon diaphragm design uses a spring in the lens to close the 
diaphragm - just the opposite of OM. When the lens is mounted, the 
aperture lever on the body pushes the diaphragm open.

Thus the auto aperture mechanism in the body only needs to yield to the 
spring in the lens to close the diaphragm as part of the exposure. The 
"power" stroke against the spring on a Nikon body occurs in reopening 
the diaphragm after the shot, when a bit of radial vibration doesn't 
matter.

The design difference, the fact that the high end mechanical bodies (at 
least the F2) have a mechanism to both lock up the mirror and stop down 
the diaphragm and the greater sheer mass of the bodies made them 
superior to the OM-1 and 2 bodies in that respect. Didn't stop me from 
switching. :-)

Moose

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