> 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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