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From: Bill Tuthill on 29 Aug 2005 13:27
One semi-frequently asked question is whether the Tamron or Sigma 18-200
is better. Over the weekend I looked at back issues of Popular Photography
and recorded SQF scores for these two lenses, and the Sigma 18-125 as well.
Here are grades for 20x enlargements. Although the Tamron scores better
at 50/16,22 and at 100/11, the Sigma 18-200 has better numerical grades
throughout its range, especially wide open (where it counts).

The 18-125 is the best of the three lenses, mostly on the strength of its
excellent scores at 50mm wide open (if you can call f/4.5 wide), which
performance probably extends to focal lengths near 50. Furthermore its
numeric scores within a single grade are almost always higher than the
other two lenses. Grades for 18-125, Sigma 18-200, Tamron 18-200:

18mm 50mm 125 100mm 200mm
3.5,4 B B C+
4.5 B B C+ A B+ B+
5.6 B B C+ A B B+ B B B x D D
8 B B C+ A B B+ B B B x C C
11 B B C+ B+ B+ B+ B B B+ x C C
16 C+ C+ C+ B+ B B+ B B B x C C
22 C+ C+ C+ C+ C+ B C+ C+ C+ x D D

Personally I don't like to even use lenses that yield poor results
at some focal length, so for me the 126-200 range is less than useless
in both the Tamron 18-200 and Sigma 18-200. It's hard to know where
between 100 and 200mm the performance trails off so much.

I hope Pop Photo tests the Minolta 18-70 for comparison with the above.
Seems like a test of the Canon 17-85 EFS IS is due shortly.

(Apologies for not posting in r.p.d.slr-systems, still don't get it.)

From: bmoag on 31 Aug 2005 14:22
Take PopPhoto results with a grain of advertiser paid for salt.
They gave a good review to the Nikon 55-200 lens which, after personal
experience, I would consider possibly the worst lens ever issued by Nikon
and virtually unusable. For one thing, you can time how long it takes on
average to autofocus with your wristwatch. One look through this lens at a
high contrast area or any point light source will tell you that this lens
has fatal optical flaws.

The Sigma and Tamron digital only 18-whatever lenses are not Leica single
focal length lenses and if you obsess over those kinds of numbers you should
not consider this type of lens. They are made for convenience, for example
travelling. It is foolish to look for the kind of performance from these
lenses that you would expect from shorter range zooms or single focal length
lenses.

These newer digital only lenses are much better than the 28-200/300 genre
for 35mm cameras in terms of contrast, sharpness and distortion probably
because they only have to cover the smaller digital sensor.

Having used the Sigma I can tell you it performs excellently at the 55-200
range for practical use, far better than the Nikon. I would agree with the
PopPhoto review that the Sigma has distortion at the widest focal length,
but it is not much worse than the Nikon kit lens and easily dealt with in
Photoshop if it bothers you.




From: Bill Tuthill on 1 Sep 2005 17:42
bmoag <aetoo(a)hotmail.com> wrote:
> Take PopPhoto results with a grain of advertiser paid for salt.
> They gave a good review to the Nikon 55-200 lens which, after personal
> experience, I would consider possibly the worst lens ever issued by Nikon
> and virtually unusable. For one thing, you can time how long it takes on
> average to autofocus with your wristwatch. One look through this lens at a
> high contrast area or any point light source will tell you that this lens
> has fatal optical flaws.

Interesting personal experience! I *was* surprised by the high scores
of the 55-200. Another problem: changing DSLR lenses is an open invitation
to dust particles on the sensor. Welcome, come on in, make white specks!

> The Sigma and Tamron digital only 18-whatever lenses are not Leica single
> focal length lenses and if you obsess over those kinds of numbers you should
> not consider this type of lens. They are made for convenience, for example
> travelling. It is foolish to look for the kind of performance from these
> lenses that you would expect from shorter range zooms or single focal length
> lenses.

It remains interesting to see how much better two lenses are than one,
optically. The Sigma 18-125 paired with Tamron 70-300 (both have the same
size 62 filter thread) is far superior to an 18-200.

> These newer digital only lenses are much better than the 28-200/300 genre
> for 35mm cameras in terms of contrast, sharpness and distortion probably
> because they only have to cover the smaller digital sensor.

Right, that's my theory. Despite the lack of interest in Pop Photo,
one of their recent issues compared equivalent focal lengths of these
new 18-200 lenses with the slightly older full-circle 28-300s.

> Having used the Sigma I can tell you it performs excellently at the 55-200
> range for practical use, far better than the Nikon. I would agree with the
> PopPhoto review that the Sigma has distortion at the widest focal length,
> but it is not much worse than the Nikon kit lens and easily dealt with in
> Photoshop if it bothers you.

Yikes, that's not what the SQF said. (Back to uranium comments on SQF)

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