TAKO. INTERNET SEIT 1996.
Olympus-OM

[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: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Thu, 17 Apr 2008 19:38:13 -0400
Thanks, that finally explains for me the normally open vs. normally 
closed lens designs.  Never had a Nikon and never had a working Pentax.

Chuck Norcutt

Moose wrote:
> 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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