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Old Jun 30, 2010, 8:08 PM   #1
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Default Kenko Teleplus MC7 DG 2X TeleConverter. OR ?

Gday all.

I'm looking for a TC that will work on my K10/20D cameras.

I have a DA*200mmF2.8 lens and a Sigma 70-200mmF2.8II Macro lens that i want to use with a TC.

I read the posts on the 1.4 and 1.5 Kenko TC. From that i gather that the Kenko TCs work on the Pentax cameras.

I tryed the Sigma 2x TC. But that does not work.

The trouble i have is finding Kenko TCs in Australia. Or anywhere.

But i finaly found some Kenko 2x TC here in Australia. The shop tells me that AF will work with the 2 lenses i have stated above. Any lens that is a F4 or faster, AF will work they say. ( I was told that about the Sigma 2xTC, but it didn't work)

Anyway What one should i get ?

The Kenko Teleplus MC7 DG 2X TeleConverter Ptx

Or the Kenko 2x MC4 Teleconverter Pentax

Has anyone got any info on either of these TCs.

What one would you get. They are both the same price at $329.00 AU.
Can't find any info to tell me about each TC. So have no idea.

Can anyone offer any advice.

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Old Jul 1, 2010, 2:29 AM   #2
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hmmm interesting - sadly cant tell you if the kenko telephoto converter will work but i was thinking about the sigma 70-200 f2.8 and saw that even for pentax mount was stated as autofocus for both the 1.4 and 2x teleconverters from sigma

it did say this though

"AF function of Pentax mounts cannot be used with SFX/SF7 cameras."

can anyone clarify what sfx/sf7 cameras are?
Pentax-DA 12-24mm f4 | Pentax-DA* 16-50mm f2.8 | Pentax-A 50mm f1.4 | Tamron 90mm f2.8 Macro | Pentax-DA* 60-250mm f4 | Sigma 150-500mm
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Old Jul 1, 2010, 4:39 AM   #3
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"AF function of Pentax mounts cannot be used with SFX/SF7 cameras."

can anyone clarify what sfx/sf7 cameras are?
John, I've no experience of either, but I believe they were just earlier models of Pentax film cameras. ... Jack.
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Old Jul 1, 2010, 6:53 PM   #4
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John. yes all info about the Sigma TC will tell you they work on Pentax cameras. But i can asure you they don't. I have tryed them, both 1x4 and the 2x do not work in AF despite what they say. I had both Sigma TC replaced, told they were faulty. After the second set didn't work, someone at the shop also tested them with a Pentax K20D and Sigma 70-200mmF2.8. The Sigma TC also sent the settings all crazy when the TC was attached. Speed and apature settings would jump all over the place. Not stoping on any one setting.
I was advised by the Australian importer of Pentax and Sigma not to use Sigma TCs on my Pentax K20d and K10D as it could damage the camera.

So i am now looking at what i can get.

Kenko looks like the only option.

Last edited by Craig66; Jul 1, 2010 at 6:57 PM.
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Old Jul 3, 2010, 3:13 AM   #5
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Hi Craig,

Sigma has yet to offer an HSM/SDM compatible TC, so the DA* 200 will not AF with any K-mount Sigma TC yet made. If you look at the back of your lens, you'll see two gold contacts between the rear lens element and the lens mount. These power the SDM motor for the DA*, and any HSM AF focusing Sigma lens which uses an in-lens motor for AF. None of the Sigma TCs made to date have these contacts, and from what I understand, only some of the Kenkos and Tamrons have had them. BTW, Sigma TCs will work with other brand lenses, as long as
1. They AF via "screw drive" motor in the camera body, and
2. The lens that you want to use it with has a recessed rear element, as the Sigma TCs were designed with a front element that protrudes and will not physically fit on a lens with a rear element that's flush with the lens mount, and
3. The lens has a maximum aperture that gives you a wider effective aperture (lower f# value) than f8 when you multiply the max Av by the magnification factor of the TC. The closer to f8 your effective max Av, the less effective the AF performance would be the general rule, and this would be true of any TC.

The Kenkos and Tamrons are generally considered by most to be the same TCs, just rebadged, and the ones that have the contacts are usually designated somewhere with a "PZ" in the model designation. PZ stands for Power Zoom, a feature offered in some FA series zoom lenses and some film SLR models. PZ is not fully supported in any of the Pentax DSLRs. Pentax uses the same electrical contacts as they used for PZ lenses to transfer power to their in-lens focusing motors. Consequently, TCs with PZ contacts are capable of being used for SDM/HSM lenses, but the compatibility is not necessarily complete, as some SDM lenses have been found to just hunt, never finding focus reliably, unless the lens' focus is already very close, and it just needs a very minor adjustment. Some users have stated that PZ designated Kenko and Tamron TCs work with their Pentax SDM lenses and Sigma HSM lenses, but all I can tell you from personal experience is that my Tamron F 1.4x AF PZ MC4 does not play well with my only SDM lens (a DA* 50-135/2.8), and displays the "hunt without finding a lock" behavior.

The only "TC" that offers complete AF compatibility for SDM/HSM K mount lenses is the Pentax F 1.7x Auto Focusing Adapter, which was officially discontinued by Pentax quite a while ago, but a number of new ones appeared within the last year from either one or two Chinese dealers. This is unique to Pentax piece -- it was designed to allow AF with manual focus lenses, and the Auto Focusing elements are contained within the body of the adapter. It gives full range AF with a 50mm lens (with the lens focused to infinity), but with tele lenses, the distance range is limited, so you have to manually prefocus the lens to get within the adapters range, then let the adapter do the fine focus adjustment. Since such an adapter needs some thickness for the movement of the focusing elements, it must also extend the focal length of the lens, and it does this by a factor of 1.7x, so most consider this to be a 1.7x TC.

Considering that the most common lens for any of the film era SLRS is a 50mm, and the fact that these lenses are usually pretty good optically, the 1.7s AFA needed good optics, and IMO, this is the case. I have a few of them, and use them with premium tele primes and zooms. There is little or no noticeable image degradation, and the short throw of the focusing mechanism makes the AF lock very quick once the lens is focused within the AFAs range. It probably sounds like a PIA to manually prefocus, but once I got the drill, it's second nature, and I actually prefer to use an AFA with my lenses because it acts as a focus limiter and gives me very quick AF.

These occasionally are available on the used market, but in the past few years, people have found out just how good they are, so they are relatively expensive -- mostly offered in the $320-350 range, but I've seen them go much higher. Personally, I paid quite a bit less for each of mine, and the last one I bought was from KEH, in EX condition, and it was $218 shipped -- last year, so deals can be found if your patient, persistent, and quick.

Sorry for the long post, but the matter of TCs for Pentax DSLRs is a very confusing subject, and SDM/HSM and some questionable testimonials by users just makes it worse. I figured that explaining why the TCs might or might not work would give you a better basis for making a choice.

BTW, I'm assuming that your Sigma 70-200/2.8 is the newest HSM version, so either of your lenses would need a "PZ" designated TC to have any chance of AF, and you'd still be taking a chance, IMO, with one of these. IMO also, the MC7 version would give you better optical performance -- "MC"=Multicoated, and the "7" means that it has 7 lens elements, and usually the more the better for a given magnification in a TC.

Most of my pics I've posted here were with at least the 1.7x AFA, so if you click on my nick in this post and look for "Find all threads started by snostorm" under the "Statistics" tab, you can see a lot of samples, if your interested.

If you have any other questions, feel free to ask, either in this thread, or by PM.

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Old Jul 3, 2010, 7:15 PM   #6
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Hi Craig, I bought my Pentax 1.7 TC from Micheal's Camera Store in Melbourne a year or so ago for $175.00 and haven't seen one since, you might have to keep looking for a while to find one. It works fine on my K10D with my DA*300 as long as you manually focus to about the correct focus and let the TC do the final check and adjust.
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Old Jul 24, 2010, 7:34 PM   #7
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Thanks for the help.

Think i will give the MC7 a go. As the shop has told me if i am not happy with the results i can return it for a refund.

Found a page with many different TC for Pentax. http://www1.shopping.com/xPP-telecon..._teleconverter

But i think i'll stick with the Aussie shop. In case i need to return it.
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