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Old Aug 16, 2009, 9:58 PM   #1
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Default Teleconverters for 70-200m f/2.8 Lens

I've been considering picking up a 70-200mm f/2.8 lens for a while now and it may happen by the fall. I've been leaning toward the Tamron which, despite the lack of HSM, seems a bit sharper than the Sigma. Did I mention that I really wish Pentax offered a digital-specific lens like this - priced in the $700-$800 range like the Tamron and Sigma? The closest is the 60-250mm f/4 at $1300.

Now, occasionally I would enjoy the added reach that a teleconverter would bring to this kind of lens. I should note that I am a big believer in using teleconverters intended for a given lens - I think it makes a big difference in image quality.

But I can't seem to find any new Tamron - or even Pentax - teleconverters (preferably 2x for an effective 600mm at f/5.6). Sigma does offer both 1.4x and 2x teleconverters designed for its 70-200mm f/2.8 lens. B&H offers Kenko teleconverters for the Tamron lens. I've heard - via some other forums - that the Kenko is actually a Tamron. Does anyone know if this is true?

For that matter, does anyone have any suggestions for me? I expect any converter to provide full autofocus and metering for a given lens.
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Old Aug 16, 2009, 11:37 PM   #2
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Originally Posted by Biro View Post
I've been considering picking up a 70-200mm f/2.8 lens for a while now and it may happen by the fall. I've been leaning toward the Tamron which, despite the lack of HSM, seems a bit sharper than the Sigma. Did I mention that I really wish Pentax offered a digital-specific lens like this - priced in the $700-$800 range like the Tamron and Sigma? The closest is the 60-250mm f/4 at $1300.

Now, occasionally I would enjoy the added reach that a teleconverter would bring to this kind of lens. I should note that I am a big believer in using teleconverters intended for a given lens - I think it makes a big difference in image quality.

But I can't seem to find any new Tamron - or even Pentax - teleconverters (preferably 2x for an effective 600mm at f/5.6). Sigma does offer both 1.4x and 2x teleconverters designed for its 70-200mm f/2.8 lens. B&H offers Kenko teleconverters for the Tamron lens. I've heard - via some other forums - that the Kenko is actually a Tamron. Does anyone know if this is true?

For that matter, does anyone have any suggestions for me? I expect any converter to provide full autofocus and metering for a given lens.
Since the digital age began and before actually, the teleconverter has gone out of fashion. The reduction in quality that results most of the time from tele use has taken away their popularity. I've heard the Tamron and Kenko are the same and since I own a Sigma that is matched to Sigma lenses ..I cannot recomend it for other lens than those that are matched to them. Most other lenses just won't mount to them. The lens element nearest to the lens you wish to mount sticks out so far it hits the back element and will not allow most lens to work with it. My Sigma "Bigma" will but it is one of the lenses the TC is matched too. The Kenko I believe will work with all K mount lenses.
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Old Aug 17, 2009, 2:25 AM   #3
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Hi biro,

I use TCs a lot. Whether a given TC will give you good optical performance is, in my experience, dependant on both the TC and the particular lens. A pretty safe general statement would be that premium primes show the least IQ degradation, and only the best zooms will stand up to critical TC use. An example of this would be my experience with my two 80-200/2.8s. I have an MF Tamron SP 80-200/2.8 Adaptall2 and a Tokina 80-200 AT-X Pro AF II. The Tamron is optically superior, and handles 1.4x-1.7x TC use pretty well. The Tokina doesn't give me satisfactory results with any of my TCs, though it's a pretty good lens overall.

The best of the 1.4x AF TCs for K-mount from an optics standpoint are the Tamron F 1.4x PZ AF MC4 and the Kenko 1.5x PZ AF. AFAIK, they were discontinued sometime in the last year, so availability is ???? new. I've heard enough reports that they are identical physically over the years that I tend to believe this even tho it's never been admitted to by the mfgs AFAIK. Not far behind is the Sigma 1.4x APO and APO DG models which have the protruding front element that Dawg mentioned. Both my 80-200s have recessed rear elements, so I would say that the new Tamron zoom probably also has this, but this should be confirmed before considering this combo. Though the Tamron/Kenko is a touch sharper, the Sigma is considerably more robustly built. I use a Sigma 1.4x APO with my 300/2.8s mainly because of the difference in build quality -- I just feel more secure using the Sigma with the big glass. . . and I'm not sacrificing much in IQ.

Most 2x TCs leave something to be desired in IQ, in my experience. I can't speak for either the Sigma 2x, the Tamron/Kenko 2x MC7, or the MF Pentax A 2X-L since I don't own them, but reports are that these all work well. I have three MF 2x TCs, a Vivitar "A" 2x Macro Focusing TC, a Tamron SP 01 2x TC for Adaptall 2, and a Pentax A 2X-S, and all of these degrade IQ more than stacking the Tamron and Sigma 1.4xs (which also gets you to 2x).

I'd say it's a pretty safe bet that either the Tamron/Kenko or the Sigma would work acceptably with the new Tamron 70-200/2.8, but only you can decide whether the IQ is satisfactory for your use. Another factor is that the Sigma is almost twice as expensive as the Tamron was las listed at. I got a used one at a good price, but I'd have to question paying 2x the price for a TC for the build quality alone. . .

One more caveat -- though you didn't mention it, the Sigma 70-200/2.8 APO DG Macro HSM would not AF with the current Sigma EX 1.4x or 2x APO DG TCs as far as I know -- they don't have SDM (HSM) electrical contacts, so they'd turn the lens into MF only. In-lens AF motor lenses can work with Tamron/Kenko TCs that specify "PZ" in their names since they have the PZ (Power Zoom) contacts that Pentax now uses to power their SDM lenses, but (in my experience specifically with my DA*50-135 SDM lens) the AF doesn't work acceptably with any of my 4 different SDM capable bodies. Other users have had differing experiences, so this is not set in stone -- but one should be aware that these TCs MIGHT not AF as expected.

BTW, Pentax used to make the FA* 80-200/2.8 which is pretty much universally accepted as easily the best optical performer of the AF zooms in this range for the mount. They could probably pretty easily adapt the optical formula to a new * class zoom, but it wouldn't be even close to the prices of the current Tamron and Sigmas. I'd imagine that it would be Weather Resistant, which would be nice. . .but my guess is that it would be priced somehwere between $1500-2000USD (which is about what they currently go for used. . . if you can find one). I doubt that Pentax is planning on reintroducing a new version of this lens, with what seems to be their current plan of replacing FA lenses with crop sensor equivalent FOV DAs.

Scott
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Old Aug 17, 2009, 11:35 AM   #4
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Thanks guys. I was considering these Kenkos:

http://www.bhphotovideo.com/c/produc...Converter.html

http://www.bhphotovideo.com/c/produc...Converter.html

It looks like if I want to buy new, these may be my only choices... other than going for the Sigma lens and TC. There is a $99 2x TC from Kenko, but I'm not even considering that. Thanks again, your input was very helpful.
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Old Aug 18, 2009, 6:02 AM   #5
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Quote:
Originally Posted by Biro View Post
Thanks guys. I was considering these Kenkos:

http://www.bhphotovideo.com/c/produc...Converter.html

http://www.bhphotovideo.com/c/produc...Converter.html

It looks like if I want to buy new, these may be my only choices... other than going for the Sigma lens and TC. There is a $99 2x TC from Kenko, but I'm not even considering that. Thanks again, your input was very helpful.
Both are not recommended first for IQ and 2nd for price.
The best set up for TC is the the SDM 1.4 or or 1.5x for DA*200mm. Zooms with multi additional elements , at least for me, is not suitable to mate with TC at all. But it sounds good on paper only.
Best bet is for you to get either Tamron or Sigma 70-200mm first see how well it goes

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Old Aug 18, 2009, 9:29 AM   #6
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Originally Posted by danielchtong View Post
Both are not recommended first for IQ and 2nd for price.
The best set up for TC is the the SDM 1.4 or or 1.5x for DA*200mm. Zooms with multi additional elements , at least for me, is not suitable to mate with TC at all. But it sounds good on paper only.
Best bet is for you to get either Tamron or Sigma 70-200mm first see how well it goes

Daniel
Interesting. I have an inexpensive Quantaray 2X TC that I picked up, that looks just like the Sigma TC's. It was very cheap ($30) and brand new, so it was a low risk toy. I haven't really used it, but I will try it on my new DA* 200MM lens and see what happens.
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Old Aug 18, 2009, 5:05 PM   #7
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Originally Posted by jnanpentaxfan View Post
Interesting. I have an inexpensive Quantaray 2X TC that I picked up, that looks just like the Sigma TC's. It was very cheap ($30) and brand new, so it was a low risk toy. I haven't really used it, but I will try it on my new DA* 200MM lens and see what happens.
Let us know how it goes.
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Old Aug 26, 2009, 4:34 AM   #8
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I have some good luck with a TC and my older manual lenses. This may not be the way you wish to go but for certain lens TC combination's, the TC can make a meaningful difference. You have to experiment to find out which ones can work though. Here are a couple of photos taken with a Vivitar 300mm f/5.6 TX lens and a Vivitar 2X-22 TC from 35-40 feet distance. Not too shabby to me. But you have to be the judge of the IQ and whether or not it will suit you. Thus the experimenting begins. LOL
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Old Aug 26, 2009, 12:17 PM   #9
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Not bad at all, Dawg. Thanks for posting.
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Old Aug 27, 2009, 9:56 PM   #10
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if you can try before you buy would be great...
i've never had a great experience using 2xTCs + a zoom lens.. i'm old world tho..
try before you buy.. just my 2..
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