.
Got this lens today along with the D90 (ducking tomatoes,) and thought I'd give
some thoughts on it here since it's available in K-mount also.
I was only able to try a half-dozen handheld shots in fading light, then a couple
hundred shots in kinda dim tungsten, so take that into account.
1st Impressions:
1) AF speed - (HSM II ring motor) on the D90 is the fastest-focusing zoom/body
combo I've ever used. It's AF-lock speed is comparable to my DA 40ltd on the
K20D in good light - very fast. It blows me away that I can even make that
comparison.
2) 50mm wide-open: Superb. Comparable to the DA* 50-135.
3) 135mm wide open: Pretty good - comparable to the 50-135, maybe a little
softer.
4) 150mm wide open:
Distance: 10 feet+ : Adequate
5 - 10 feet: so-so
under 5 feet: kinda bad
At close-focus distances, I saw noticeable FF. It was to the degree that it was
apparent and consistent, and I was considering my options - send in to Sigma
for adjustment, or return to B&H for replacement copy.
I did a bit more research, and it appears that this may not actually be a fixable
issue - it may be a design limitation of this lens. Photozone had a copy
adjusted by Sigma, and here's what Klaus noted, even with this tweaked copy:
Quote: The Sigma was able to produce very impressive resolution figures in the MTF lab.
This is especially true for the 50mm and 100mm setting where the center to
border characteristic is generally excellent from f/2.8 down to f/8 (apart from a
few very good+ border and extreme corner portions). At 150mm there's a drop
in quality specifically at f/2.8 - the center and border is still very good but the
extreme border quality drops down to only fair quality here. However, the
corners do pretty much catch up by f/4. The peak performance is reached between
f/5.6-f/8 with an excellent center and very good borders/corners.
It is worth to mention that this doesn't seem to be the complete story.
At 150mm I wasn't really able to get any good field images from this lens at
very close focus distances (<1.5m). The contrast level is very poor here (SAMPLE).
To be fair this is normal up to some degree for all non-macro lenses but in my
opinion Sigma should have chosen a more conservative minimum focus distance.
So, I have a feeling that I'm not going to have much luck trying to get it adjusted,
or hoping for something different with a replacement copy. There's even a
chance that an adjustment by Sigma may improve the close-focus performance
at 150mm f/2.8 at the expense of some other FL.
As a reality check, I shot some of the same targets with my K20D + 50-135,
and the 50-135 smoked the Sigma in close-focus targets wide-open. At 50,
85, 110, 135mm, at 10 feet or greater, they were pretty close, and I was
quite impressed with the Sigma.
So.... Super-fast focus, sharp up to about 135mm, not a great performer from
135mm --> 150mm and quite sub-par in close-focus at 135mm+.
What to do? Send it back and get the Tokina 50-135 2.8 for Nikon mount?
Live with the Sigma's limitations and enjoy the super-fast AF and forget
about close-focus with this combo?
Guess there's no free lunch.
.
Last edited by jsherman999; 02-25-2009 at 10:23 PM.