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[OM] Teleconverters - which ones to use?

Subject: [OM] Teleconverters - which ones to use?
From: "Tom Trottier" <infoanim@xxxxxx>
Date: Wed, 12 May 1999 22:24:05 -0400
That's a slight simplification. I believe that the position of the auto 
lever on an OM lens tells the camera how many stops down from the 
maximum aperture size of the lens that the lens is set for. 

So the teleconverter would have to transmit this info too. That way, 
manual & spot metering can be done at the biggest aperture size. I 
wonder what the maximum stop range is that can be recognised?

[P.S. don't you just love recipricols? bigger = smaller-number]

I think it gets slightly messed up for zoom lenses if the max aperture 
varies with the focal length and measurements are taken at a focal 
length different from the focal length used to take the picture.

Tom

> Date: Wed, 12 May 1999 06:22:45 -0400
> From: Chuck Norcutt <norcutt@xxxxxxx>
> Subject: [OM] Teleconverters - which ones  to use?
> 
> On: Tue, 11 May 1999 20:59:15 
> Dan Lau <dlau@xxxxxxxxxxxxxxxx> wrote:
> 
> This brought up a question that I've always wanted to know about
> teleconverters.  I use an OM-1(n) camera, do the teleconverters
> automatically account for the shift in aperture in transmitting
> the information to the OM-1(n) body?  In other words, when a
> teleconverter is mounted, should I continue to use the "center
> the needle and shoot" method or must I do some mental compensation
> for the loss of light (i.e., center the needle first, then open
> it up two-stops for the 2X and so on).  Thanks.
>         -Dan
> - ---------------------------------------------------------
> 
> If your camera did not have TTL metering you would have to do exactly the
> sorts of mental gymnastics you describe.  For a 2X converter you would
> have to increase the exposure by 2 stops from whatever was indicated on
> the lens aperture ring.
> 
> Due to the wonders of TTL metering though you don't have to do any of
> that.  The teleconverter doesn't pass any information to the camera since
> the camera doesn't need to know anything about the lens aperture. It
> measures the light it sees and combines that with film speed to give a
> recommended shutter speed.  It doesn't care if the light was a bright
> light coming through a small hole or a dimmer light coming through a large
> hole.
> 
> The TTL metering is also what allows you to use macro or microscope
> setups without doing even more complicated exposure calculations. 
> Except for situations like backlighting that can fool the meter it
> doesn't matter what is attached to the camera as a lens.  Just center the
> meter needle.
> 
> Chuck Norcutt
------------------
From: Tom Trottier, President, ACT Productions Inc.
infoanim@xxxxxx                   http://www.act.ca
+1 613 594-4829                 fax +1 613 594-8944
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"Make it as simple as possible, but no simpler" - Einstein

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