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Old Oct 30, 2007, 9:20 PM   #11
TDN
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danielchtong wrote:
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Sigma zoom has quite a few version of f2.8. I got myself a 24-60mm EX DG. And my daughter 18-50mm EX DG macro (still untested and she seems to be ok). And yours 28-70mm F2.8.
Anybody did some comparison among them?
Just curious.

Daniel
I have no idea how they compare, but mine is the first (oldest) "EX" version, so not the new DG version.

From what i read Sigma appears to make 3 versions of this lens, the Aspherical (the one I got), the Aspherical DF (Dual Focus), and the DG (digital coatings)



Then there's also a 24-70mm EX macro DF but that one's more expensive.

From what I can tell from the few test shots I took, the extra letters and "macro" on more recent lenses seem to be more marketing than anything else. My lens focuses pretty closely, to 40cm, and if you look up the specs of the lenses with "macro" on them, the minimum focusing distance is the same!

The only real difference is that the DF has a special focus mechanism (focus ring doesnt move with AF) and the DG is more compact.

Tom

P.S.: I noticed that AF is much faster on this lens than on any other lens I have! Probably the f2.8 working
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Old Oct 31, 2007, 8:32 AM   #12
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Some test samples:

f2.8



full size

f2.8



full size

f8



full size


I'm happy with the sharpness. It's not nearly as sharp as a prime, but when focused correctly, it's definitly sharp enough. Especially with some USM afterwards I have a feeling this one will be usable wide open at concerts, which is why I got it.

AF is fast enough, although it tends to focus more on the background than on the subject. I'm not used to using AF, so it might be me...I'll need some practice with this lens.


I'll post some real (not test shots) photos in another thread

Tom
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Old Nov 1, 2007, 6:32 PM   #13
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Tom,

If you want to experiment more with the AF, try changing the AF Point. Try either the Center point or Select (user selectable). This'll force the AF to focus on either the center point or the point chosen, respectively.

Jon
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