Chuck Norcutt wrote:
> I don't know anything about this particular Sigma but our own Moose here
> is extremely happy with his 28-300 Tamron in EOS mount. You find lots
> of complaints on the web about quality control of Sigma lenses but I
> think these complaints are typically only about the bottom of the price
> line. Some of the higher end Sigmas are excellent performers.
>
When I was looking for a "do everything" lens, I chose the Tamron
28-300/3.5-6.3 XR Di based mostly on a Pop Photo review. Pop Photo had
also reviewed the Sigma, giving it lower performance ratings but noting
that it might be good value for the low price.
On the web, there was hardly any info on the Tamron, which was a new
model. There were user reviews of the Sigma, which were not encouraging,
varying wildly from "junk" to not bad for what it is and what it costs.
One good place to see user reviews is
<http://www.fredmiranda.com/reviews/>. The current average review rating
for the Sigma is 4.8 and 6.5 for the Tamron.
As Chuck says, I've been very happy with the Tamron. Once reviews
started showing up, I was puzzled by how bad some of them were. Reading
in detail, I saw that there were several complaints about sharpness at
the long end (This is also a common theme in reviews of the Sigma.) I've
come to the conclusion that many of those complaints are a result of
user error. Many people don't seem to realize that faster shutter speeds
are needed as focal length gets longer. The old rule of thumb for hand
holding is 1/fl, so a 300 mm lens would require at least 1/300 sec. But
that is for average, printable quality. Many who shoot for quality would
require a faster speed and obviously some people are steadier than others.
However, even less common seems to be an understanding that, for the
same size display/print from a smaller sensor camera, like the E-500,
the amount by which the image is enlarged is greater, which enlarges any
motion blur more. For a 2x factor sensor like the Olys, 300 mm requires
at least 1/600 sec. for hand held use.
Another complication is that smaller sensor cameras will show different
results with the same lens than will film or full frame digital bodies.
The Oly bodies have so called 4/3 sensors, which are about half the size
of a 35 mm film frame. So when you use a lens designed to cover 35 mm,
only the "heart" of the image will be recorded. Thus, a person reporting
on a lens using a small sensor body may well come to different
conclusions about its performance than someone using the full frame area.
Here are some examples taken with the Tamron and the Can*n 300D, which
has some of the same small sensor effect as the E-500, although not as
much <http://www.moosemystic.net/Gallery/Tam28-300/>. And here are some
more with inset full pixel samples of center and corner sharpness at
various focal lengths
<http://www.moosemystic.net/Gallery/MPhotos/TamSharp/>.
I wouldn't have gone to all this talking about all this, but you have
expressed a general interest in learning about this stuff. So here's
another lesson you may not like so much. Many AF lenses that are
available for Can*n, Nik*n, Pentax and maybe Konica, are not available
in mounts for the E-500. Nor are they adaptable to the E-series bodies
like old manual focus lenses are. And both the Sigma and Tamron 28-300
lenses are among those not (yet?) available in 4/3 mount. Sorry.... :-(
> But you do need to understand that a 28-300 zoom lens is a real optical
> compromise and may exhibit some artifacts of that. On the other hand it
> will allow you to get a lot of shots you might otherwise miss if you had
> to change lenses to get it.
Based on my research, I wouldn't buy the Sigma. Based on my experience,
now including full frame, I would buy the Tamron again in a heartbeat.
Unlike sigma, Tamron has a good rep for QC, but maybe I just got an
extra good one. I don't know, but I like it a lot.
> Also, if I was on a safari in Kenya rumbling across some arid grasslands I
> don't think I'd be interested in
> changing lenses very often in the dust and dirt.
>
I certainly agree. I also find fewer shots missed with a wide range zoom
where lens changes aren't needed so often.
Moose
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