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08-04-2009, 01:09 PM   #1
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sigma 1,4 x teleconverter

Hi guys, can someone tell me if the Sigma 1,4 x is compatible with autofocus of Pentax 300 4.5 EDIF* and PENTAX DA* 300mm f/4,0 ED [IF] SDM?

08-04-2009, 01:48 PM   #2
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probably not

aside from issues relating to the lack of the power contacts that are part of the KAF2 mount, the sigma TC has a unique requirement.

It requires that there is a free space inside your lens, approximately 35mm in diameter 10mm deep.

this is because the front element actually sticks out a little on the sigma TCs.

SIgma TCs are designed for only a handfull of lenses, not even the full sigma range
08-04-2009, 02:28 PM   #3
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Then not only have to wait for the pentax tc; who knows when!!!

Thank you.
08-04-2009, 04:02 PM   #4
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I am sure the Tammy 1.4x is SDM compatible though. I am using one right now with a DA*300mm. Its the Tamron-F model for short. PZ-AF MC4 model for long.

08-04-2009, 04:29 PM   #5
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Hi nunzio,

The Sigma EX 1.4x APO TC works fine with the FA*300/4.5 as this lens has a recessed rear element. The Tamron F PZ AF MC4 also works find. I don't personally know if the Tamron will AF correctly with SDM, as mine doesn't with my DA* 50-135 -- it hunts and quits unacceptably unless the actual focus distance is within inches of where the lens is set.

In my experience, the Sigma, while significantly more expensive than the Tamron/Kenko, is not quite as good optically, but it's build quality seems considerably more robust. The IQ results are so close that it really doesn't make much of a difference, but I use the Sigma with my AF 300/2.8s (Sigma EX 300/2.8 APO, and FA*300.2,8) for peace of mind.

Scott

Scott
08-04-2009, 07:22 PM   #6
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...and I can only speak for the DA*300mm. The Tammy-F will AF fine under normal light with that lens. I saw a specification table somewhere the Tammy was meant for lenses of 100mm and greater so that may speak to the issues with a 50-135mm lens if true.
08-04-2009, 11:02 PM   #7
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QuoteOriginally posted by imtheguy Quote
...and I can only speak for the DA*300mm. The Tammy-F will AF fine under normal light with that lens. I saw a specification table somewhere the Tammy was meant for lenses of 100mm and greater so that may speak to the issues with a 50-135mm lens if true.
Hi Lee,

Thanks for the vote of confidence regarding my integrity!

I have no doubt that your combo works for you, and unlike your reference to my post, I never questioned the veracity of your information -- I just stated that I didn't know. . . and I thought this might be relevant to the OP.

I think that a universal statement that this lens and TC will AF reliably with SDM is not necessarily justified, especially after it's been pretty well documented that Tamron/Kenko PZ AF TC compatibility with SDM lenses and bodies is a bit sketchy.
If this is no longer the case, then my apologies for posting misleading info, as this was not my intention.

I don't think that it's coincidental that Kenko/Tamron seemed to discontinue this series of TCs close to the time that SDM lenses started to be released. It would seem to me that it would be a feather in their cap to have the only SDM compatible TCs available on the market. . . but what do I know? It's quite possible that Pentax has addressed this in later production SDM lenses, but I haven't heard anything from them concerning this, so I let my personal experience stand.

My experience with the 4 SDM capable bodies that I currently have (K100DS, K10, K20, and K-7) with my copies of the DA*50-135 (a very early one, and I tested it at 135mm, by the way) and the Tamron F 1.4x TC is that AF is unacceptable with this combo. All 4 bodies react the same way -- it gets close, hunts 3 times, then gives up. Repeat this 2-3 times, and it will lock focus and take a good image. I'd rather just shoot with my A*200/2.8, or any of the other lenses I have that cover 200mm with reasonable speed. I've read a number of posts by others who've had the same experience. I think it's pretty safe to say that the problem is in the lens, and since I never anticipated shooting this lens with a TC -- and that the lens is out of warranty, I have no plans to do anything about it so I guess I'll never know. . .

BTW, I doubt that any recommendation that Tamron might have made about using a TC with lenses under 100mm would have anything to do with AF compatibility -- especially Pentax SDM which didn't even exist when the TC was designed . . . more likely that they knew that using one with shorter FLs would yield little FL advantage, and would probably result in more significant degradation of lens performance (or might cut into potential future lens sales).

Scott
08-04-2009, 11:33 PM   #8
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QuoteOriginally posted by snostorm Quote
Hi Lee,

Thanks for the vote of confidence regarding my integrity!


Scott
sigh......ok, i don't ever mean to casually offend anybody in the forums. Since you believe I questioned your integrity, Scott, I apologize. It was not intended. All of the statements you make through the rest of your email are correct.

I can't recall where I ran across the table of TC's and recommended lens sizes (it was for all existing TCs) but I do recall this huge thread on TC's that the OP may want to dig through since there is bound to be new information for him in it. Enjoy.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/19694-tamron-t...rter-pics.html

08-05-2009, 02:33 PM   #9
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I forgot to specify in my post, I was talking about APO TELE CONVERTER 1.4x EX DG.
Perhaps this has caused confusion with the old converter for film cameras.
Now I can perhaps consider the possibility to buy it.

Thank you all

Last edited by nunzio; 08-05-2009 at 02:40 PM.
08-05-2009, 05:52 PM   #10
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the only difference between the APO 1.4X EX teleconverter and the APO 1.4X EX DG teleconverter is the coating on the rear element.

the sigma TCs can only work with a lens that has a resessed rear element it needs to be 35mm in diameter and 10 mm recess
08-06-2009, 01:11 PM   #11
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QuoteOriginally posted by Lowell Goudge Quote
the only difference between the APO 1.4X EX teleconverter and the APO 1.4X EX DG teleconverter is the coating on the rear element.

the sigma TCs can only work with a lens that has a resessed rear element it needs to be 35mm in diameter and 10 mm recess
Thank you Lowell
08-11-2009, 10:38 AM   #12
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I've purchased the tc Sigma 1,4x DG EX.
It works fine on my 300/4,5.
Thank you all.
08-11-2009, 11:26 AM   #13
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QuoteOriginally posted by imtheguy Quote
I am sure the Tammy 1.4x is SDM compatible though. I am using one right now with a DA*300mm. Its the Tamron-F model for short. PZ-AF MC4 model for long.
Where can I buy a Tamron PZ-AF MC4...a quick look in the usual places turned up nothing.
Any ideas?
08-11-2009, 11:45 AM   #14
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QuoteOriginally posted by jbcampbell Quote
Where can I buy a Tamron PZ-AF MC4...a quick look in the usual places turned up nothing.
Any ideas?
Since they are out of production you just have to get lucky. I found mine on Amazon from somebody selling their collection of 3 lenses. I bought it to test out with a rented DA*300mm as a try before I buy. Also testing it with my DA55-300mm. So far pretty happy with it. The lens rental company asked ME where I got it as they would like to stock a few also.
08-11-2009, 03:03 PM   #15
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I have the Tammy TC and tested it on my 55-300: slows down AF considerably - almost to the point of being unusable for me. I have it to use on my Tamron 70-200, which it seems to be more compatible with and keeps up with the AF speed of that of the 70-200 mounted on its own...
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