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01-15-2019, 06:17 PM   #1
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vintage teleconverters on modern zoom with no aperture ring? Help needed.

Hi all, I am new to this forum. I just picked up a 70-200 f2.8 Tamron. I'll eventually pick up a modern teleconverter that allows auto focus and transmits all the info from the lens to the camera.
But for the moment I happen to have a very old 2X APX Teleplus MC4 teleconverter kicking around so I threw that on to see how it works and surprisingly it is not too bad when used with the stop down metering green button like you would a manual vintage lens.
The one problem is I have no idea what aperture I am on. Can anyone help with this? I believe if I set the aperture when the lens is on without the teleconverter then turn the camera off and throw the converter and lens on, then turn it back on, the lens should have the same aperture as when I set it without the teleconverter?
Does anyone know if this is true, or if there is another sneak around? Surely someone out there has played around with old teleconverters on digital dslrs? Although I couldn't find anything on this out there in webland.
Any help would be greatly appreciated.
Cheers guys & girls.

01-15-2019, 06:27 PM   #2
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The Tamron 70-200mm has an aperture ring, right? The actual F stop will be 2 stops slower than what's selected on the ring and you'll be able to get the correct exposure by following the stop-down metering procedure.

For KAF3 or older lenses without an aperture ring, a manual teleconverter cannot be used because it will always be stopped down to the minimum aperture. One way to avoid this would be to snip the aperture lever on the TC, which would then get the lens to always shoot wide-open.

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01-15-2019, 07:19 PM   #3
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Canon is the brand that you have to set lens aperture and then pull it off. The Canon ef lenses have electronic aperture. Pentax other than the new kaf4 lenses like the 55-300 plm doesn't have this issue.

With a lens without the aperture ring you need a tele converter that works with A series lenses and allows the camera to set aperture. The f stops reported will be off by 2 stops but this also affects wide open so it is mostly an exif issue.
01-16-2019, 02:20 AM   #4
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QuoteOriginally posted by col.hutchins Quote
Hi all, I am new to this forum. I just picked up a 70-200 f2.8 Tamron. I'll eventually pick up a modern teleconverter that allows auto focus and transmits all the info from the lens to the camera.
But for the moment I happen to have a very old 2X APX Teleplus MC4 teleconverter kicking around so I threw that on to see how it works and surprisingly it is not too bad when used with the stop down metering green button like you would a manual vintage lens.
The one problem is I have no idea what aperture I am on. Can anyone help with this? I believe if I set the aperture when the lens is on without the teleconverter then turn the camera off and throw the converter and lens on, then turn it back on, the lens should have the same aperture as when I set it without the teleconverter?
Does anyone know if this is true, or if there is another sneak around? Surely someone out there has played around with old teleconverters on digital dslrs? Although I couldn't find anything on this out there in webland.
Any help would be greatly appreciated.
Cheers guys & girls.


I'm an enthusiastic user of 2x converters and I also have a Tamron 90-300mm with no aperture ring (amongst others), but I don't ever remember using a lens with no aperture ring with a 2x converter !


- goes away, grabs lens and converters then returns to computer -


Sorry, no results of any real help ... my Sigma EX 2x converter (with a/f and 7 contacts) simply won't fit on the Tamron lens. The Teleplus MC7 2x, with 6 contacts but m/f only, won't allow control of the aperture at all on my K-5 or my K-70. The Tamron SP 'F System' 2x with no contacts at all allows the K-5 (but not the K-70) to close the aperture with no indication of to what setting.


So, all in all, it would appear one needs a full-function 2x to get any control at all and then make sure it mechanically fits the lens before parting with money


Good luck

01-16-2019, 03:16 AM   #5
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As pointed out above an "A" type TC with electrical contacts will allow you to control the aperture except on KAF4 lenses. The TC will not compensate for the speed or f-stop loss, nor will it vary the maximum aperture on variable aperture zooms (e.g. f4-5.6 zooms). There are AF TCs from the KAF film era that have screw drive shafts and the 7th "data" pin but they are sort of rare to find. To work with KAF4 lenses the TC would need to have the power zoom contacts as well.
01-16-2019, 09:20 PM   #6
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QuoteOriginally posted by Adam Quote
For KAF3 or older lenses without an aperture ring, a manual teleconverter cannot be used because it will always be stopped down to the minimum aperture. One way to avoid this would be to snip the aperture lever on the TC, which would then get the lens to always shoot wide-open.
Thanks, this was what I wasn't sure about. What a shame it stops down to minimum aperture.
01-16-2019, 09:20 PM   #7
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Thanks all for the information above. All was helpful and yep as I expected need a better TC.
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