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04-17-2010, 04:33 AM   #1
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Are there any issues using sigma teleconverters?

I was in the store today and saw a used Sigma 2x for a steal, but when I asked about it the camera store guy warned me off it saying it would only work with some lenses / could break my lenses that weren't sigmas!

I couldn't get where he was coming from. Its a pentax k mount and transmits power and data, same as the pricy one on sigma's website so what gives?

After looking all I could find was that HSM doesnt work with the Teleconverter. Has anybody here used / heard of problems? I would be using it primarily with an f4 70 - 210 mm A series zoom.

Also, with 2X magnification, how many stops of light am I really going to lose? Also all I really want it for is moon shots and some daylight birding, but will the hit in sharpness be really bad? Ive never used this kind of attachment before, but I can hardly afford a 500 mm lens to 'do it right.'

Thanks in advance!

04-17-2010, 05:08 AM   #2
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I assume you are talking about a sigma APO 2X EX teleconverter.

These are specifically designed to work only with a very limited number of long fast Sigma (and some pentax) lenses.

the reason is that the front element of the TC protrudes 12mm into the rear of the lens.

as a result your lens must have a 35mm diameter 12mm deep recess in the center to even mount the TC.

They are excellent but not a general use teleconverter. Consider them "Matched" to long fast lenses.

there are other threads that list the lenses the TC is mechanically compatable with

Note also, the SIGMA TCs as of the time I write this., do not support HSM>

Additionally these TCs feed lens data streight throug, with no modification, causing the camera to report and use the values of aperture and focal length driect from th elens.

For shake reduction, the compensation is for a lens 1/2 the effective focal length, and in some cases (K10 and K20 specifically) the incorrect aperture reporting causes metering errors, which have alos been well documented in the forums
04-17-2010, 12:38 PM   #3
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very informative! thank you. I will take my target lens down there tomorrow and see if it works. I think it has a rather large recess in the back but im not sure its that big.

and sorry, I did run a google on the forum but I guess I was in too much of a hurry
04-17-2010, 02:42 PM   #4
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What is the target lens?

I can probably tell you in advance

04-17-2010, 02:45 PM   #5
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See this post

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/40883-sigma-ap...tml#post383865
04-20-2010, 03:08 AM   #6
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How much is the Sigma 2x APO TC this worth used?
05-21-2010, 07:00 AM   #7
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Hi guys, sorry I didn't get back to this thread as I was off travelling. I went ahead and bought the converter, and in the end I'm not too happy;

I use it with the Pentax-A 70-210, and it just barely fits into the back. Unfortunately it won't focus to infinity (but only REALLY infinity) as I found out when I tried a moon shot.

Other problems with the combo are that the travel of the focus ring is only about 40 degrees now, and just breathing will take it out of focus. The focus lock indicator is very iffy now, and ....

All the shots are soft, but this is most times due to the troubles locking focus. If you can nail it then its no big problem

QuoteOriginally posted by Lowell Goudge Quote
What is the target lens?

I can probably tell you in advance
Pentax-A 70-210 F4

At one point I wasn't thinking and almost jammed my beloved M 50 / 1.4 on it without thinking. That definitely won't fit!

Thanks for the linkage!

QuoteOriginally posted by rustynail925 Quote
How much is the Sigma 2x APO TC this worth used?
I got it for a little over 5,000 yen.

Any offers on buying it? should work well with a big 2.8 lens, and the optics are perfect. (Oops I guess that is not allowed outside the marketplace )

Here are some pics where I managed to get the focus, but still I lost so much light from an F4 lens that I was pushing the ISO quite high on a medium bright day:







12-05-2010, 10:05 PM   #8
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If attach the Sigma 2x APO DG with DA* 200mm and SDM-enabled bodies, you cannot enter camera menu and exposure value keep changing. SDM is not function too.

This teleconverter works perfectly with DA*200mm and MZ-S by screw-driven AF.
12-06-2010, 07:17 AM   #9
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Jesse

I suspect your problems are due to mechanical interference with the rear element of the zoom hitting the frong element of the TC. It really is only recommended for very very few lenses.

Arm_jstp- Does the TC actually fit on the DA200? I am surprised if it does.
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