Not that it necessarily invalidates a comparative test but I think
you'll find that 2X TCs are not designed for and are not recommended for
lenses as wide as 35mm. Sigma does not recommend usage below 50mm,
Tamron not recommended below 90mm, Canon not below 140mm and Nikon not
below 70mm. Your results on the TC test might be quite different if you
tested a 100mm with 2X vs a 200mm.
Chuck Norcutt
On 9/29/2011 6:44 PM, Chris Trask wrote:
>>
> The lens used here is once again a Tokina 28-70mm RMC. For the baseline
> photo the FL is 70mm and the aperture is f:8. For the photos with the three
> teleconverters the FL is 35mm and the aperture is f:5.6. Shutter speed is
> 1/500. Focusing is done at f:3.5.
>
> Clarity was judged by way of an area of fairly fine text, which afforded
> evaluation inevery direction on the subject plane. Compared with the
> baseline photo, the clarity with the Sigma 7-element X2 teleconverter is all
> but exactly the same. The Vivitar X2 telemacro is a close second, while the
> Soligor 3-element X2 is last.
>
> With regard to colour, the Soligor was a bit lighter in the reds and
> oranges while the Sigma and Vivitar were virtually unaltered. Yellows,
> greens, and blues were the same for all three.
>
> This test reaffirms my years-long impression of the 7-element Sigma, and
> gives me added confidence that the Vivitar telemacro is a worthy piece of
> field macro equipment.
>
> Chris
>
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