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[OM] Re: PLEASE QUIT!!!!

Subject: [OM] Re: PLEASE QUIT!!!!
From: "Wayne Harridge" <wayneharridge@xxxxxxxxxxxxxxx>
Date: Thu, 1 Mar 2007 21:50:57 +1100
> I no longer have a Tamron 90mm lens, and therefore cannot 
> test it myself on a digital body, but I believe others have 
> found that the flat rear element causes reflections off the 
> sensor, making it unsuitable for use on a digital body.  But 
> it appears you already have the lens, so you could test for 
> that yourself.
> 

I have noticed that.  Try photographing an evenly lit surface with the lens
stopped down to f16, you should see a "hot spot" in the centre of the frame.
I presume at larger apertures there is a general lowering of contrast over
the entire image.  I know there were several variations over time of the
Tamron 90 macro, some variants may behave differently.  The Sigma 90/2.8 and
the Vivitar 90/2.5 do not exhibit this behaviour, so there are alternatives.
In testing just about all my lenses, Zuiko, Nikkor and a few 3rd party I
only noticed this effect with the Tamron 90/2.5 and the Nikon Series E
50/1.8.  Film users who think they are exempt from this effect need to test.
I could duplicate the effect with the Tamron 90/2.5 on an OM body using
film, though it was not as obvious as with the E-300.

...Wayne


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