Thys wrote:
Though not a great believer of lens tests myself, it is interesting to note
a lens test of macro lenses in this month's (April) of Practical Photography
(British mag) that tested the MTF's of allmost all brand names. The Sigma
and Tamron (and Minolta 100mm) got the same final score as the Canon (9/10)
which could be related to the respective price of the 3 but the Canon is
mostly sharper than the the other two. The Tamron and Sigma seems to perform
on par with the Canon in the centre MTF, but loses out at the edges.
(Actually, at f2.8, the Sigma and Tamron both performs slightly better than
the Canon in the centre but worse at the edges)
The big disappointment from a Canon perspective from this article is how
badly the 50mm/f2.5 fared in edge resolution wide open against the others.
Other 'losers' include the Nikon 105, Pentax 100 and other 100's like
Cosina, Vivitar, Soligor and Tokina.
I think, judged from this summarized (probably one-lens only) test, all
three are excellent lenses, but my vote would still go to the Canon if you
can afford it, for consistency(better QC), better edge resolution, build,
future compatibility and USM. Off course if the older Canon 100mm is brought
into comparison, you would lose USM and get poorer build but retain the
excellent optics (from my experience)
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The only headache with the Sigma is newer EOS bodies may require you to
upgrade the chip inside he lens. Usually Sgima does this for free on newer
lenses. As to tests, I don't know about the way Practical Photographer does
it but I will say that Pop Photo also did some testing and the lenses rated
in order Tamron 90mm, Sigma 105mm, Canon 100mm. For half the price I put up
with the Sigma. My only complaint is the screw in hood. Other than that, the
lens is terrific.
Photodo also rates the Tamron slighlty better than the Sigma but this can be
pretty much ignored when you consider the focal lengths are different. BTW,
Pop Photo tests interestingly enough seem to always agree with the Photodo
MTF tests.
Tamron Weighted MTF for 90 mm: f2,8 0,79, f4 0,83, f8 0,84
Sigma Weighted MTF for 105 mm: f2,8 0,77, f4 0,81, f8 0,83
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