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11-05-2014, 02:11 PM   #1
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Extension tube recommendation

Extension tube recommendations anybody? Really don’t like the idea of a reversing ring (I do have one) but was thinking of getting a set of tubes to use with my sigma 70mm. Any and all advice and know how greatfully recived

11-05-2014, 03:16 PM   #2
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The sigma 70mm has no aperture ring (macro lenses without aperture rings are very limited in their use on bellows/reversed etc.), so you need tubes with A contacts.
11-05-2014, 03:22 PM   #3
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QuoteOriginally posted by glasbak Quote
The sigma 70mm has no aperture ring (macro lenses without aperture rings are very limited in their use on bellows/reversed etc.), so you need tubes with A contacts.
, thanks this had been mentioned to me before.. seem very scarce on the ground
11-05-2014, 03:26 PM   #4
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buy a scratched teleconverter on ebay and unscrew the glass.

11-05-2014, 04:01 PM   #5
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I have one available already deglassed if you are interested. PM me if you want and we can discuss.
11-05-2014, 04:07 PM   #6
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The teleconverter on its own can also be OK.

I have an older pentax set of rings that will do the aperture. You could try and get a second hand set - but must be able to do aperture.


Oops sorry this is for the Q - looks like they removed the K mount - however you should have a look. The link I saved no longer goes to the K mount product
(Pentax Q Auto Extension Tube Set | Macro | SRB-Photographic.co.uk there are a number of people on this blog that have used some of their products, so check the thread first)
11-05-2014, 04:15 PM   #7
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QuoteOriginally posted by Bob from Aus Quote
Oops sorry this is for the Q - looks like they removed the K mount - however you should have a look.
They tried K mount extension tubes with screw drive,
but it seems that they didn't really work that well,
so reputable dealers stopped offering them.
11-05-2014, 06:58 PM   #8
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In my experience the Sigma 70 does not match well with the typical A-type teleconverter used to make an extension tube. The Sigma (and some other DA lenses I've tried) will not show the correct aperture on the TC. I think it needs the 7th contact to work correctly.

11-05-2014, 07:18 PM   #9
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QuoteOriginally posted by baro-nite Quote
In my experience the Sigma 70 does not match well with the typical A-type teleconverter used to make an extension tube. The Sigma (and some other DA lenses I've tried) will not show the correct aperture on the TC. I think it needs the 7th contact to work correctly.
Thank you, that was the bit of info nobody seemed to supply even my local pentax specialist
11-05-2014, 08:00 PM   #10
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QuoteOriginally posted by maltfalc Quote
buy a scratched teleconverter on ebay and unscrew the glass.
^ this post is going to drive prices of scratched teleconverters up. good idea.
11-19-2014, 02:01 PM   #11
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QuoteOriginally posted by rrstuff Quote
^ this post is going to drive prices of scratched teleconverters up. good idea.
i have some for sale.
11-19-2014, 02:13 PM   #12
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If you need to explore the effect of extension rings simply cut various lengths of paper towel/toilet paper cores and temporarily position the lens to see/compare the results.

Last edited by pacerr; 11-19-2014 at 02:19 PM.
11-19-2014, 02:36 PM   #13
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QuoteOriginally posted by baro-nite Quote
In my experience the Sigma 70 does not match well with the typical A-type teleconverter used to make an extension tube. The Sigma (and some other DA lenses I've tried) will not show the correct aperture on the TC. I think it needs the 7th contact to work correctly.
Can it be something else?

I used A-type teleconverters (deglassed to make extension tubes) with a few Sigma lenses. The tubes were a variety of 6-contact and 7-contact types. All worked OK.

The 6-contact type, if the matting surface with the camera is anodized, needs to have the area where the 7th contact would be scrapped to make ground contact (a strip of aluminum foil also works).

Last edited by SOldBear; 11-19-2014 at 04:15 PM.
11-20-2014, 07:40 AM   #14
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QuoteOriginally posted by SOldBear Quote
Can it be something else?

I used A-type teleconverters (deglassed to make extension tubes) with a few Sigma lenses. The tubes were a variety of 6-contact and 7-contact types. All worked OK.

The 6-contact type, if the matting surface with the camera is anodized, needs to have the area where the 7th contact would be scrapped to make ground contact (a strip of aluminum foil also works).
Certainly could be something else, but I would't know what. None of the TCs I've tried this with have had the anodized surface. Have the Sigma lenses you've tried had aperture rings? The 70 macro doesn't.

Same issue with the few DA lenses I've tried. DA* lenses work fine with an A-type TC, however.
11-20-2014, 10:10 AM   #15
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QuoteOriginally posted by baro-nite Quote
Have the Sigma lenses you've tried had aperture rings? The 70 macro doesn't.

Same issue with the few DA lenses I've tried. DA* lenses work fine with an A-type TC, however.
I just tried a 6-contact tube with the lenses in my signature. All of them worked fine. The only Sigma that has aperture ring is the 135-400.

The DA lenses worked OK too.

Please read this post regarding 6-contact vs 7-contact tubes.

Last edited by SOldBear; 11-20-2014 at 10:20 AM.
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