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Old Oct 3, 2008, 5:51 PM   #1
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Newbie here. Howdy.

I just received my Sigma 70-200 HSM F2.8 II lense. It's great, but my plans to use it with a 1.4X teleconverter were dashed when I read the pink flier that came with it. Basically it says the AF will not work with the teleconverter. HSM is not yet supported with the Pentax mount.

A call to Sigma verified this. A design is being worked on, will be available some time, but there's no schedule available. Check back next month. I've already been there with the darned lens that took years to be made available since the announcement and I don't even see an announcement from Sigma for this next teaser.

The confusing part is that many retailers state that AF is supported by the current Sigma 1.4X teleconverter - even listing this specific lense (with HSM). After talking with Sigma, I do not believe them.

Questions: what's the straight scoop? Does anyone else offer a Pentax HSM teleX?

By the way I have a K10D and following a firmware update all works will with the lense.

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Old Oct 3, 2008, 7:23 PM   #2
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I have not been following this lens release closely, but what Sigma is telling you fits with what I have read thus far. The 70-200mm is, I believe, their first HSM release for Pentax K mount. Pentax has had an HSM teleconverter on their lens roadmap but I can't tell you if it will work with the 70-200mm or not.

On a different note, I would love to see some pics and read your impressions on the 70-200mm, especially your thoughts on sharpness and focus speed. I am pretty well set on the Pentax 50-135mm but the Sigma remains a possibility if the quality is there.

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Old Oct 3, 2008, 7:40 PM   #3
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Thanks Tim.

I am pretty new to digital SLR, with my previous experience back in the stone age when I had a pretty complete B&W darkroom, tinkering with 16mm movies, 35mm SLR and some 4 X 5 stuff.

Bottom line, I would not consider myself an expert in any sense of the word. I will attempt to make some comparisons soon.

What I can tell you now is that the Sigma 70-200 construction is far superior to the Pentax 55-300 (non-DA*) I purchased to fill the gap till the Sigma became available. I am an engineer and was a bit disapointed with the mechanical construction of the Pentax lens, though it takes good photos. The Sigma has very solid construction and feel. The HSM focus is completely silent, and the manual override is fantastic - totally brainless and no bit of jerkiness or complaint from the lens. Unfortunately I do not have a DA* to compare.
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Old Oct 3, 2008, 9:16 PM   #4
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From what I've read on various bulletin boards, a particular Kenko TC will support HSM - the TC that was designed for the PZ cameras (it has the extra contacts). People say that their DA* lenses will work with the HSM focusing motors using this TC. If I understood one discussion I read, this TC has been discontinued and you aren't assured of getting one when you buy on-line, since there's also a non-PZ version also. I don't have a TC so I'm speaking only about what I've read, not personal experience.

The Pentax TC is supposed to be out next year - it was introduced at Photokina a few weeks ago (though it appeared on the lens roadmap a year ago). It will have the contacts to support HSM.
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Old Oct 4, 2008, 12:50 AM   #5
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Hi sparkie,

Welcome to the forum and congrats on the K10 and the Sigma 70-200.

The only information that I can supply is my experience with the Tamron F 1.4x TC and the DA* 50-135. This TC has the necessary contacts for the in-lens motor, and while the camera can drive the motor, the AF action is sketchy. The Tamron TC is generally considered a rebadge of the Kenko 1.5x, BTW.

In bright light or dim, the lens/TC hunts full lock 3 times,then gives up without finding focus -- then when I try AF again, the same thing happens. On the 3rd or 4th try, it will immediately lock focus. I have heard that there are some users of this combination that have no such problems. Luckily, I had no plans to use a TC with this lens.

Apparently, there is some strange slight incompatibility -- but this is with a Pentax lens. My understanding is that Sigma reverse engineers the focusing systems of the camera mfgs to make their lenses compatible, so it's possible that there are some differences as to exactly how the camera body communicates with the a Sigma as opposed to a Pentax SDM lens.

The assumption is that the new Pentax SDM TC will work with any screw drive or internal motor Pentax KAF2 lens. I only have the slightest lingering doubt that they will. Sigma will have some motivation to develop their own Pentax HSM TC since they've announced a number of HSM teles and zooms for Pentax, but I doubt that it's a really high priority for them with Pentax's small market share.

All that being said, the bottom line is that either the Tamron or the Kenko might work with your Sigma, but I don't think that there's any testimonial evidence that it will or won't -- the lens is too new.

Sorry if that doesn't help much. . .

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