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Old Feb 6, 2009, 8:43 PM   #31
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And another
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Old Feb 6, 2009, 8:45 PM   #32
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Here is the group I have right now that fits the Sigma APO TC.

The Sigma 100-300 lens will only fit the TC when using the Homemade lens extension tube. You loose infinity focus when you do this.
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Old Feb 6, 2009, 9:35 PM   #33
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The Sigma APO TCs are 'Matched' teleconverters. That is they only work with a few lenses. For what they do tehy are very good. But if you need a TC to use with any other lens, you need one of Sigma's or Kenko's 'Generic' teleconverters. They are lower quality and less expensive, but they'll work with anything including other generic teleconverters. So I wouldn't say Sigma's APO TCs were 'ill conceived'. I'd say they're just 'specialized'.
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Old Feb 7, 2009, 9:15 AM   #34
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As I've show above they work with more tan just the lens on that list. I too would advise the original poster here to get a different one than the Sigma APO TC. But for me I have a plethora of lens to choose from that will work with this TC. This one was given to me and I fully intend to keep using it with numerous lens that do not appear on this list. Just hope he can find your Generic TC and it will hook up with his AF and AE.

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Old Feb 7, 2009, 1:08 PM   #36
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My understanding the Kenkos are no longer made. You may find them on ebay or some stock at B&H or Adorama or some other outlet but the production has ended...is this not so?

The Sigma ones you list are the Matched ones you say will only fit the lens on your list...I have one and it is a proprietary Matched TC designed for the most part to go with their lenses, though as I've shown they will fit other lens if you hunt for them. The Tamron one you can find on Ebay though rarely for a good price and the Kenkos to me are the ones to look for, Though they are going up in price as week converse..

My statement that they were ill advised to build their TC's as they did was because there are so many folks out there without Sigma lens that are looking every day for a good and inexpensive TC to buy and use. Their TC's that are produced now are still designed to fit mainly their lens. A little more design work and thousands of photogs would have Auto TC's to use. The only thing holding it back is the outer flange needs to be made a tad higher to eliminate the lens to lens contact that now prevents them from being used.

Here are somre you left out..

http://www.adorama.com/PRO2XPX.html

They are out of this one..http://www.adorama.com/LN15XKPXAFDG....amp;item_no=51

They have this one in stock..
http://www.adorama.com/LN2X4KPXAFDG.html

And this one...
http://www.adorama.com/LN2XKPXAFDG.h...&item_no=2

B&H has the same for about the same price. I guess Kenko's demise is reported a little prematurely...ain't it a wonder about thye missinformation going around.

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Old Feb 7, 2009, 5:10 PM   #37
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bigdawg wrote:
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My understanding the Kenkos are no longer made. You may find them on ebay or some stock at B&H or Adorama or some other outlet but the production has ended...is this not so?
Kenko's website [ http://www.kenko-tokina.co.jp/e/] still lists them, as does the website oftheir exclusive US Distributor, THK Photo [ http://www.thkphoto.com/products/kenko/kenko-03.html ].

bigdawg wrote:
Quote:
The Sigma ones you list are the Matched ones you say will only fit the lens on your list...I have one and it is a proprietary Matched TC designed for the most part to go with their lenses, though as I've shown they will fit other lens if you hunt for them.
The list I provided a link to is of the Sigma lenses that Sigma says their APO TC can be used with. Certain OEM and other third party lenses will fit, as you have shown. But as you pointed out, the front element of the Sigma APO TC sticks out beyond the female lens mount, so many lenses won't work with it. The Sigma APO TCs are some of the finest available.

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... The only thing holding it back is the outer flange needs to be made a tad higher to eliminate the lens to lens contact that now prevents them from being used.
You can't shift the optical elments with respect to the mount, and still keep the same optical properties. Otherwise, you could just put an extension tube in front of it and use it with any lens. You would still get the longer focal length, but you wouldn't be able to focus at infinity.

That's not a design flaw. It's a characteristic of one of the best teleconverters available, and if that means most inexpensive lenses won't work with it, ...
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Old Feb 7, 2009, 7:03 PM   #38
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Guy...I have one....it will with care go down to 58mm. I always move it out to 100mm to mount but from there it will zoom down to 58mm. As to the design being the only way then jeez how can all the other TC's work so well. I still believe they did it so you'd need just their lens to make it fit. Good marketing ploy i guess but it still to me was a little short sighted. How many more sales could they have made if they hadn't gone that route?

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Old Feb 7, 2009, 9:30 PM   #39
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bigdawg wrote:
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... As to the design being the only way then jeez how can all the other TC's work so well. ...
They don't work as well as the Sigma APO DG.

That's why the Sigma 1.4x EX DG APO costs $219 and the Kenko Teleplus "DG" 1.5x AF costs $87!

The Sigma EX DG APO TCs are the best third party teleconvertersavailable, followed closely by the Kenko TelePlus Pro 300 (and Tamron SP). All the other third party TCs are generic, so they'll work with anything, but their performance isn't nearly as good as the Sigma APO, Kenko Pro 300 and Tamron SP.
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Old Feb 8, 2009, 12:16 AM   #40
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TCav wrote:
Quote:
bigdawg wrote:
Quote:
... As to the design being the only way then jeez how can all the other TC's work so well. ...
They don't work as well as the Sigma APO DG.

That's why the Sigma 1.4x EX DG APO costs $219 and the Kenko Teleplus "DG" 1.5x AF costs $87!

The Sigma EX DG APO TCs are the best third party teleconvertersĀ*available, followed closely by the Kenko TelePlus Pro 300 (and Tamron SP). All the other third party TCs are generic, so they'll work with anything, but their performance isn't nearly as good as the Sigma APO, Kenko Pro 300 and Tamron SP.
Hi TCav,

I have to disagree with you, at least to some degree. The Tamron F AF MC4 1.4x TC is, IMO arguably as good as, or by some criteria, optically better than the Sigma EX APO 1.4x AF TC.

There have been a number of comparisons published online, and the consensus seems to be that the Tamron is a touch sharper in the center, though it is softer at the edges. The Sigma, though softer at the center, is more consistent towards the edges -- personally, I require center sharpness. The edges, for my purposes, are usually significantly OOF anyway. Here's a link to a PDF of one such test -- pretty well done. . .:

http://www.prime-junta.net/pont/Revi...Sigma_1.4x.pdf

My own tests did show the same, though they weren't anywhere near as carefully done as those I've seen posted -- I tend to not just believe what I read, and like to at least confirm findings for myself. To be fair, the differences are only really visible at relatively high magnification, so for all practical purposes, and for all but the most disriminating, they are negligible, IMO. In build quality, the Sigmas do smoke the Tamron F -- in this aspect, there is no question.

The Kenko Pro and Tamron SPs are irrelevant in this forum since, AFAIK, they never made them for the Pentax K. I've never seen tests comparing them (and really don't care, since I can't use what hasn't been made). I think that Sigma made a mistake in designing their TCs to only really mate with long teles with recessed rear elements -- and it was a significant mistake to not make it 100% compatible with their biggest selling ultra tele zoom, the Bigma. Their second mistake was to only list Sigma lenses in their compatibility chart -- virtually eliminating those who might consider using one with either OEM or other 3rd party glass.

I personally own a Tamron F 1.4x and a Sigma EX 1.4x APO, and use them pretty much interchangeably. I tend to use the Sigma more because the build quality makes for increased peace of mind with $1K+ lenses hanging off it. I'm kinda casually looking for an inexpensive Pentax Rear Converter 1.4x-L to stack on my 1.7x AFA.

I'm also looking forward to the supposedly soon-to-be-released Pentax 1.4x SDM TC. Hopefully it'll be a very good one. . .

Scott
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