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Re: [OM] Tamron SP 350mm f5.6 mirror lens

Subject: Re: [OM] Tamron SP 350mm f5.6 mirror lens
From: "Mickey Trageser" <mickeytr@xxxxxxxxxxxxxxx>
Date: Thu, 15 Mar 2001 21:00:51 -0500
Well, yes, I understand the relationship between the silicon cells and the
aperture and shutter speed. What I hadn't considered is that the open
aperture metering is counting stops from open, not a position that is
calibrated to represent f1.4, f1.8, f2, f3.5, f3.8, f4 etc. But of course,
it is simpler as you describe. And the f8 of a mirrored lens doesn't
represent a potential amount of light to pass, like a glass lens f stop
implies. It simply relates the calculated ratio of dimensions.
Unfortunately, it's misleading in common practice. But I'm glad to have
learned something valuable again. :-)  Darn good thing the OM meters are so
good!

Thanks for you help, Warren!
Mickey
----- Original Message -----
From: <WKato@xxxxxxx>
To: <olympus@xxxxxxxxxxxxxxx>
Sent: Wednesday, March 14, 2001 10:41 PM
Subject: Re: [OM] Tamron SP 350mm f5.6 mirror lens


>
> The meter measures whatever hits the silicon cells. If a cloud crosses the
sun, if there is only candlelight, or whatever the light conditions are, it
will measure it. To the Olympus all lens are at full aperture, unless told
otherwise.  Mirror lens are measured at full aperture because this is what
the position of the aperture lever at the rear of the lens tells the camera.
Lens with aperture control tell the camera, 1. I'm wide open, 2. I'm stopped
down one stop, 3. I'm stopped down 2 stops, etc., etc.  For 2 & 3, the
shutter speed has to lenghthen by 2x or 4x. In the Olympus system the actual
aperture is not communicated to the meter, only the number of stops from
full open is.
>
> I hope that this is not too confusing.
>
> Warren
>
>
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