Which one to buy: Tamron SP 180mm F/3.5 Di Macro or Sigma ..

John Sheehy hastily wrote in


> Frankly, I don't see *any* extra resolution with the Sigmas in the B&W
> resolution tests (of course, there would definitely be extra
> resolution in red/blue resolution tests). If I try to decide where
> both the 10D and the SD10 start to "fail" (failure to resolve in the
> case of the 10D, and failure to be accurate in the SD10), the ratio I
> find is almost exactly the ratio of the pixel pitches; IOW, they have
> the same true, honest, B&W luminance resolution relative to pixel
> pitch. The Sigma simply takes the liberty of misrepresenting more
> detail than it should.

Sorry, I wrote that the wrong way. What I meant was "linear pixel
density"; not "pixel pitch".

IOW, If I try to decide where
both the 10D and the SD10 start to "fail" (failure to resolve in the
case of the 10D, and failure to be accurate in the SD10), the ratio I
find is almost exactly the ratio of the linear pixel densities; IOW, they
have the same true, honest, B&W luminance resolution relative to linear
pixel density. The Sigma simply takes the liberty of misrepresenting
more detail than it should.


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John P Sheehy
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