I was recently asking about this lens. Hearing no major horror stories about
this or similar lenses, and having some of my concerns about compatibility put
to rest by the Sigma technical folks (kudos to them for a quick, concise, and
on-target email response to my query), I bought one from Adorama. The price was
a couple hundred dollars higher than I had remembered from a few weeks ago when
I started looking. I don't know if that is poor memory or a supply-demand
adjustment.
First impressions and observations:
1. Not as heavy as I feared. On the other hand,
2. It is clear that plastic is well represented in the overall makeup of the
lens. Seems to be good quality plastic, but still.
3. The in-lens AF system operates on HSM which is compatible with my K20 HSM.
Knowing nothing about the underlying technology, I consider this to be a minor
miracle. Multiple manufacturers are using the same technology in a way that
allows them to be cross compatible! Wow!
4. The AF allows manual override if the body's AF is on AF-S.
5. The AF is more of an AF-assisted MF. I.e., you could probably brew an
espresso in the time it takes to find focus if you start with the lens on
close-up and ask it to focus on something close to infinity. It reminds me of
using the Pentax F-1.7x extender with a manual lens, a similar need to
pre-focus the lens.
6. However, if you have the lens zone-focused in the general neighborhood of
your subject, the AF seems quick and precise with no unseemly dithering.
7. The lens has an Optical Stabilization (OS) system.
a. they say you can use the OS, or the camera's SR, but not both at the
same time.
b. the OS seems to work. I haven't really given it a workout yet.
c. it is nice to have an in-lens OS on a long lens; I have trouble hand
holding anything longer than a 250 or 300 because I can't get a good sense of
focus with the image in the viewfinder moving around so much.
8. The OS has 3 modes: Off (recommended to avoid execess power consumption), 1,
and 2. The instructions are not clear on the difference between 1 and 2, but I
think 2 is for shooting race cars or speed skaters or other targets moving
horizontally while 1 is for general scenes where either nothing is moving
(other than the camera in the hands of the unsteady photographer who had too
much coffee) or the subject(s) exhibit random unpredictable movement around the
scene like in a hockey game or a kids soccer game.
9. The lens is not weather proof.
10. The Sigma web site, the Adorama and B&H descriptions of the lens, and the
generic instruction sheet that comes with the lens all mention the Sigma 1.4x
and 2.0x extenders which will work with this lens (though in manual focus mode
only.) However, we are special! Pentax users get an extra footnote: the
Pentax-mount Sigma tele-extenders are NOT compatible with this lens. I've seen
no explanation on what the incompatibility is.
11. One other thing I almost forgot! The lens comes with a soft case which has
a shoulder strap; I have never understood why people would make cases that are
only good for storing lenses and don't have provision for carrying them in the
case. But Sigma goes a step further: they also have a shoulder strap that
attaches directly to the lens (on the tripod mount)! I don't know that I would
use it, but thanks Sigma for thinking of this.
General comment - the lens is not magical. It does sometimes miss focus. My
handheld shots at 500mm show some signs of movement not overcome by the OS. But
a few quick shots this afternoon were far better than what I have been able to
do with similar subjects in similar lighting. It is a keeper until I can find a
Pentax counterpart that performs at least as well.
For sample images (all birds) see my two blog posts from today:
http://smhalpin.posterous.com
stan
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