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09-18-2007, 02:00 PM   #1
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Sigma 70mm f/2.8 EX DG Macro AF

Hi

I am considering buying this lens, given the awards and reviews it has received. I will be using it with my K10D.

Does anyone have first-hand experience with it?

Is there a comparable lens I should consider?

The Sigma website states there are limitations due to Pentax DSLR's not having aperture rings. I am familiar with these limitations using my legacy SMC lenses but surprised to see that for a DG lens. Does anyone know what the limitations are specific with this lens?

Thanks in advance

09-18-2007, 04:18 PM   #2
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I don't have this lens and I'm only commenting regarding the compatibility.

The "DG" moniker refers only to the coatings I believe. It is not related to its use on digital or film cameras (as opposed to "DC" lenses)

The restrictions are that it will not work correctly on a camera that does not support the "A" setting on aperture ringed lenses. Which means it will fully function on any Pentax camera with the introduction of the first of the A series in the 1980's (except for the K1000).

A Pentax compatible lens without an aperture ring is equivalent to having a lens with an aperture ring permanently set to "A"

In short no issue for the K10D

cheers

Greg

Last edited by wirrah; 09-18-2007 at 04:27 PM. Reason: bit more explanation
09-18-2007, 04:27 PM   #3
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Hi,
The lens should work fine on your K10D. The only issues are with cameras that require a working aperture ring.

In that price range, you really should consider the Tamron SP AF 90mm f/2.8 Di Macro. It has a well-deserved reputation as a legendary lens and is compatible with your K10D and all preceeding K-mount cameras. See the reviews at photodo.com and photozone.de for comparison between it and the Sigma. Particularly impressive is the standard maritime museum shot.

You might also want to consider the Sigma 50mm f/2.8 DG Macro EX if you don't need the extra working distance. The 50mm has similar performance at a much lower price and bulk (I paid $236 at 47th Street Photo for mine).
09-18-2007, 04:30 PM   #4
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The "issue" is not with the K10D, it is with the Sigma 70mm lens.

There is no aperture ring on this type of lens. Therefore, the lens is, in effect, always in "A" mode . . . the aperture can only be set, electronically, by the body.

You can, however, still control the aperture. For example, if your K10D is in "M" (manual) mode, you can set the aperture by pressing the Green button or using the dial on your K10D.

09-18-2007, 04:43 PM   #5
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QuoteOriginally posted by Budson Quote
Hi

I am considering buying this lens, given the awards and reviews it has received. I will be using it with my K10D.

The Sigma website states there are limitations due to Pentax DSLR's not having aperture rings. I am familiar with these limitations using my legacy SMC lenses but surprised to see that for a DG lens. Does anyone know what the limitations are specific with this lens?
There are no limitations in using this lens with the K10D or any other Pentax digital SLR. It will work with all exposure and metering modes, and with auto-focus. It does not have the problem with the lack of an A setting that is the case with older "K" lenses and M lenses. It will work just like a DA lens, and is, in effect, always at the "A" aperture setting.

Some older Pentax film cameras require an aperture ring to control the aperture, such as my LX from the late '80s. Since the Sigma 70mm Macro lacks the ring, it won't work with the LX (unless I want to use it at only f/32). In Pentax parlance, it is equivalent in function to an "FA J" lens: full frame 35mm coverage but no aperture ring. Sigma is referring to this limitation, in case a customer wishes to use the lens with an old film camera.

The DG refers to digital compatible (enhanced anti-reflective coatings) and has nothing to do with the aperture ring compatibility issue, as another poster pointed out.
09-19-2007, 08:23 AM   #6
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Original Poster
Thanks all for the excellent information. I expected the situation as you described but I wanted to be sure prior to buyin the lens.

Budson
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