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02-12-2008, 04:32 PM   #1
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Sigma 28-70mm 2.8 | DG vs DF

Hello,

I'm about to purchase a Sigma 28-70mm f/2.8 lens.

However I'm stuck between the

28-70mm f2.8 EX DG - AU$420 shipped from B&H (costs almost $600 locally in Australia)
28-70mm f2.8 EX DF - AU$260 bought locally

What are the differences between the lens that constitutes such a price difference?

Thanks
Michael

02-12-2008, 04:52 PM   #2
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I don't know about you, but I have never heard of a DF lens.

Sigma make DG lenses (full frame) and DC lenses (ASP-C sensor)

they make 2 different 28-70 lenses, the EX DG lens is constant f2.8 the the DG lens (no EX) is a variable F2.8 - F4
02-12-2008, 06:01 PM   #3
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I have the Sigma 28-70 EX DF constant f2.8.
This is the discontinued full-frame film version of the lens.
Optically the same as the current DG (APS-C format) version but is bigger, heavier and has an aperture ring with A setting. I found various reports stating the lens was not sharp at extreme edges of images when wide open (f2.8). Using this lens on an APS-C camera avoids the extreme edges of the lens and I have found images are very sharp from edge to edge at f2.8 at all zoom ranges.
If you can live with the large size and weight, this is a good natural light indoor and late evening outdoor lens. Good range for portrait work. At 50mm compares well with my now superseded Pentax A f2 prime.

Garth
02-12-2008, 06:13 PM   #4
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I believe DF is Sigma's term for "dual focus" and refers to their "clutch" mechanism for switching between auto and manual focus on the lens. My 105mm macro had this, and it made it so the focus ring didn't rotate during autofocus.

02-12-2008, 06:17 PM   #5
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Gordon is correct. The lens has a clutch to engage auto from manual focus.
You get used to it very quickly.
02-12-2008, 07:15 PM   #6
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not to totally screw up your thinking, but whyy not the tamron 28-75 F2.8?

reported to be best in class at this range.

I wound up with this and have not regretted it in the least. I looked at sigma 24-60, 24-70 and 28-70 lenses, but like the tamron. Strange since I have both ends covered with sigmas, the 10-20 and 70-200 F2.8.
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