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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