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10-31-2011, 07:27 PM   #1
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Help needed: Sigma AF x1.4 TC

Recently I bought this TC for my FA*300/4.5. It is Sigma 1.4x pre- EX version, I believe. To my big surprise it doesn't AF on FA*300. It hunts both ways a couple of times and then it gets stuck at one end. Use of AF designated button helps a bit: sometimes it makes a few attempts and acquires focus (as visible through OOF) but never locks. It does AF on Tamron 28-75 and DA16-45 with no problem at all. In fact on sunny day with DA 16-45/4 it AF from f/4 up to f/8. I decided to return it to KEH. It happened that yesterday I purchased the Sigma 100-300/4. And there is my question. Is there really noticeable IQ difference between this non EX and EX versions? The EX version is extremely rare, but works with SDM lenses. The Sigma 100-300/4 deserves the best 1.4x TC ever. Would the latest 1.4x APO EX DG (with protruding lens element) be superior to EX? Could someone with experience in using of all of these TCs comment on their qualities and differences?
Thank you in advance,
SG

11-01-2011, 08:44 PM   #2
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Sigma 1.4x TC

Sorry for the bumping up. I really need help here. Could anybody comment on how different IQ wise is current APO EX DG version vs. older APO EX?
11-02-2011, 04:57 AM   #3
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i am a bit confused what TC you bought initially.

I have 2 sigma TCs, the APO 1.4x EX and APO 2xEX DG

the difference in these two teleconverters is only rear element coatings, which have not been an issue with my sigma APO 70-200 EX (non DG non macro)

your problem ,ay be one of a combination of things.

an F4.5 lens is right at the edge of any teleconverter locking AF, although I would have expected it to be a little more reliable than you indicate.

the question I really have is related to the TC itself, Does it have power zoom contacts? I have never heard of a sigma power zoom compatible TC. Also, does the TC have a protrruding front element? later APO TCs were designed for a very specific and limited range of long fast and expensive sigma zooms and primes, and were not General purpose TCs. i personally cant imagine one working ont he FA300/4.5

Now to your next question, using an APO 1.4x EX teleconverter on the 100-300/4 either the DG or non DG will work as long as th elens is a screw drive lens (sigma does not make an HSM TC yet for pentax) and the difference in coatings in my opinion does not gain much because sensor reflection has not been an issue with my non DG 1.4x BUT if they are the same price take the DG
11-02-2011, 01:11 PM   #4
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My Sigma 1.4x TC is still a mystery

QuoteOriginally posted by Lowell Goudge Quote
i am a bit confused what TC you bought initially.

I have 2 sigma TCs, the APO 1.4x EX and APO 2xEX DG

the difference in these two teleconverters is only rear element coatings, which have not been an issue with my sigma APO 70-200 EX (non DG non macro)

your problem ,ay be one of a combination of things.

an F4.5 lens is right at the edge of any teleconverter locking AF, although I would have expected it to be a little more reliable than you indicate.

the question I really have is related to the TC itself, Does it have power zoom contacts? I have never heard of a sigma power zoom compatible TC. Also, does the TC have a protrruding front element? later APO TCs were designed for a very specific and limited range of long fast and expensive sigma zooms and primes, and were not General purpose TCs. i personally cant imagine one working ont he FA300/4.5

Now to your next question, using an APO 1.4x EX teleconverter on the 100-300/4 either the DG or non DG will work as long as th elens is a screw drive lens (sigma does not make an HSM TC yet for pentax) and the difference in coatings in my opinion does not gain much because sensor reflection has not been an issue with my non DG 1.4x BUT if they are the same price take the DG
Lowell, Thank you very mush for the reply. My newly acquired TC is non EX, non DG older Sigma 1.4x AF. It doesn't have Pz contacts. Very strangely it auto focus on DA16-45 (up to f/8) and even DAL 55-300 at 300mm up to f/8 in a good light. However, it refuses to AF on FA*300 wide open.
I ordered Sigma APO 1.4x AF EX last night, but still have some thoughts that APO EX DG might be better choice for the Sigma 100-300/4 due to specific optimization for long tele photo lenses. Is it noticeable, BTW?
Thanks again,
SG

11-02-2011, 02:13 PM   #5
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QuoteOriginally posted by Greyser Quote
Lowell, Thank you very mush for the reply. My newly acquired TC is non EX, non DG older Sigma 1.4x AF. It doesn't have Pz contacts. Very strangely it auto focus on DA16-45 (up to f/8) and even DAL 55-300 at 300mm up to f/8 in a good light. However, it refuses to AF on FA*300 wide open.
I ordered Sigma APO 1.4x AF EX last night, but still have some thoughts that APO EX DG might be better choice for the Sigma 100-300/4 due to specific optimization for long tele photo lenses. Is it noticeable, BTW?
Thanks again,
SG
is the lens in A mode? the selected aperture on the other lenses shoudl not impact anything as the focus is wide open.

If you are not in A mode AF may not work (I am not sure, I have not tried, because there are no non A lenses that are AF.

As for the DG vs non DG I don't notice any issue, the DG designation came out after the introduction of the DIgital cameras and designates 2 specific things, first, D = Digital, as opposed to no designation which meant film. In reality it is all about non reflective coatings on the back of the rear element to prevent reflection from the sensor. Second, the G in DG (and I have no idea how they came up with this designation) identifies the lens as having a full frame capability (i.e. it projects an image circle for a 24x36mm frame (film or digital)

I do not notice any issue with my lens having reflections from the sensor (lens is also not DG) or with reflections using the 1.4x TC. TO me, the issue of sensor reflections at least with the 70-200F2.8 and the 1.4x TC are a myth, not a reality. In fact, of all my lenses (45 of them) I have only one with sensor reflection issues, and that was due not to coarings on elements but reflective metal parts in the rear of the lens.

somewhere, I posted the listing of compatible lenses with the TCs, I am not sure where now, but I don't thing the FA300/4.5 was on the list of compatible lenses for the APO series of teleconverters.
11-02-2011, 06:47 PM   #6
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QuoteOriginally posted by Lowell Goudge Quote
is the lens in A mode? the selected aperture on the other lenses shoudl not impact anything as the focus is wide open.

If you are not in A mode AF may not work (I am not sure, I have not tried, because there are no non A lenses that are AF.

As for the DG vs non DG I don't notice any issue, the DG designation came out after the introduction of the DIgital cameras and designates 2 specific things, first, D = Digital, as opposed to no designation which meant film. In reality it is all about non reflective coatings on the back of the rear element to prevent reflection from the sensor. Second, the G in DG (and I have no idea how they came up with this designation) identifies the lens as having a full frame capability (i.e. it projects an image circle for a 24x36mm frame (film or digital)

I do not notice any issue with my lens having reflections from the sensor (lens is also not DG) or with reflections using the 1.4x TC. TO me, the issue of sensor reflections at least with the 70-200F2.8 and the 1.4x TC are a myth, not a reality. In fact, of all my lenses (45 of them) I have only one with sensor reflection issues, and that was due not to coarings on elements but reflective metal parts in the rear of the lens.

somewhere, I posted the listing of compatible lenses with the TCs, I am not sure where now, but I don't thing the FA300/4.5 was on the list of compatible lenses for the APO series of teleconverters.
Of course it's in A-mode. I swapped 4 TCs one by one in the raw. 2x Bower, 1.4x Vivitar, and 1.7x AFA auto focused as a charm. The Sigma - did not. Do you know, is protruding optics of current APO EX DG 1.4x TC a part of optimization for long tele lenses?
11-02-2011, 07:30 PM   #7
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Just a question, what do you have the camera set for as far as AF points go, Multi or Centre spot? When I use any TC on my telephotos I make sure I have it set to centre position. I focus on the subject, then compose the shot.

I too use the Sigma 1.4 APO EX DG on my FA*200/2.8 and it works brilliantly on the K-7. One thing to think about could be the reduced DoF of the 300 and the fact that it is a fair bit faster than your zoom at 300, so the camera could just be struggling due to such a thin "in Focus" area of the FA lens. Just a thought.
11-02-2011, 10:37 PM   #8
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QuoteOriginally posted by cmohr Quote
Just a question, what do you have the camera set for as far as AF points go, Multi or Centre spot? When I use any TC on my telephotos I make sure I have it set to centre position. I focus on the subject, then compose the shot.

I too use the Sigma 1.4 APO EX DG on my FA*200/2.8 and it works brilliantly on the K-7. One thing to think about could be the reduced DoF of the 300 and the fact that it is a fair bit faster than your zoom at 300, so the camera could just be struggling due to such a thin "in Focus" area of the FA lens. Just a thought.
I almost exclusively use center point focus and re-compose, if needed.

11-03-2011, 06:33 AM   #9
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QuoteOriginally posted by Greyser Quote
Of course it's in A-mode. I swapped 4 TCs one by one in the raw. 2x Bower, 1.4x Vivitar, and 1.7x AFA auto focused as a charm. The Sigma - did not. Do you know, is protruding optics of current APO EX DG 1.4x TC a part of optimization for long tele lenses?
Yes, this is why the TC is only compatible with specific lenses, you need a rear lens opening 35mm in diameter and 12mm deep. it is sort of similar to the pentax rear converter - L but the L is even deeper.

here is the link to the listing of lenses from the two info sheets that came with my APO teleconverters. also check the sigma website for a more current list. As you can see, the list is not that long.

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/50537-teleconve...tml#post484259
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