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[OM] Re: Nikon AF lenseS

Subject: [OM] Re: Nikon AF lenseS
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Tue, 20 Feb 2007 10:58:57 -0500
Well said.

Chuck Norcutt

Daniel Sepke wrote:
> Allen,
> 
> This adapter is just like the majority of adapters available right now in
> that it just provides a mechanical way to mount a lens from one system on
> another and that is it.
> 
> To fully understand the situation you have to know the history of lens to
> camera communication. Please forgive my slight simplification of history to
> allow for clarity.
> 
> The earliest interchangeable lenses allowed just that, changing lenses.
> Other than a screw thread or a bayonet mount there was no communication
> between the body and the lens. The first major development was the auto
> diaphragm which allowed the body to control the aperture in the lens. This
> allowed the body to stop the aperture in the lens down at the same time as
> the shutter was released. To do this the lens and body gained a mechanical
> link to control the aperture. Prior to the auto diaphragm we had to stop the
> lens down manually prior to releasing the shutter (not a quick way of
> working). 
> 
> Light meters on the camera then started to become more common, though often
> with a meter that attached to the body as an accessory piece. The next step
> was to have a meter that allowed interaction with the lens to determine its
> setting and how that would affect the meters reading.  At this point the
> lens mount gained a second mechanical linkage to communicate the aperture
> setting to the meter. Then we move onto the light meter being built into the
> camera body and then leap further to using the camera lens as part of the
> metering system (TTL or Through The Lens metering). The additions also
> allowed for open aperture metering, which removed the need to stop the lens
> down to take a reading. By knowing the aperture setting the meter can bias
> its reading to determine what it would be as if you had stopped the aperture
> down. 
> 
> In the 1980's Canon shook all of this up and introduced the EOS System and
> changed everything about the way lenses and camera bodies communicate. They
> removed all the mechanical communication linkages and returned the mount to
> be just a way of attaching the lens to the body. In the EOS system all the
> communications are accomplished by an electrical link. Sensors and motors in
> the lens to take readings and make adjustments. This method is how the
> majority of current systems work. 
> 
> As a side bar, there are other linkages that are were developed but not as
> widely implemented. These include linkages to communicate the maximum
> aperture of the lens allowing for displaying the f stop number you have set
> in the viewfinder display. Also earlier incarnations of auto focus for
> several brands often had the focus motor built into the body and not the
> lens (makes lenses cheaper but ultimately limited focus speed).
> 
> The all electronic mount allows for full communication of the basic elements
> of the lenses settings but also offers extended communication as implemented
> by Olympus in the E System. The E System allows the lens to communicate to
> the body  additional information about vignetting that may occur when the
> lens is used wide open. The body can then adjust its processing of the image
> and correct it out of the final image. There is also a facility to allow the
> lens to communicate how to correct any optical distortion present in the
> design and adjust that out of the final image.
> 
> 
> So coming back to the adapters... The current crop of all electronic mounts
> have no way of accepting the information that the all mechanical mounts can
> offer them. These simple adapters take the highly evolved mechanical mounts
> back to the first step of development with all of the operational delays of
> the that era. What has yet to come along, and is a logical next step, is a
> hybrid translating adapter that adds sensors and motors to the adapter. Thus
> restoring the full communication and adjustments of the all mechanical mount
> and allow easier use. Saying that is much easier than doing it though!
> 
> What I have not covered in this is the reason that these adapters are even
> possible, the flange to sensor/film distance. That will be a subject for
> another time.
> 
> Hopefully this introduction will help you get a better handle on some of the
> how's and why's of using older lenses on DSLR's.
> 
> Dan S. 
> 
> -----Original Message-----
> From: olympus-owner@xxxxxxxxxx [mailto:olympus-owner@xxxxxxxxxx] On Behalf
> Of Allen Coltrin
> Subject: [OM] Nikon AF lenseS
> 
> When we were talking about not doing AF lenxes I remembered there is a Nikon
> AF to 4/3 adaptor. I assume it must work.
>  
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=014&sspagename=STRK%3AMEWA%
> 3AIT&viewitem=&item=330085243405&rd=1&rd=1
>  
> Allen
> 
> 
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> 
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