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03-13-2010, 12:47 PM   #1
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2x convertor doesn't transmit everything. Any ideas?

I picked up a Quantaray 2x AF along with some other stuff here on the forum. I'm curious about a few things. First it's optical quality is surprisingly good. Pretty sharp as you'll see from the samples below (taken with the Sigma 70-200mm f2.8 EX and all around 180mm x 2 = 360mm).

So on the camera mount side it has 7 electrical contacts and the 2 internal power drive contacts. Same on the lens mount side.

1) It doesn't transmit SDM data to my DA*16-50mm
2) AF screwdrive works fine (not the DA* but n Screwdrive only lenses).
3) Aperture data displays on the screen but it's not corrected to the 2x multiplier. So shooting at -1.0Ev will correct that.
4) Lens focal length shows up as the original lens FL in EXIF. So I assume SR is not set quite right.

So anyone have any experience with units like this and if so, is this one somehow defective? The only others I have are the Tamron 1.4TC and the Pentax 1.7 TC and both of those transmit the data correctly.

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03-13-2010, 01:01 PM   #2
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That's interesting, my Tamron 1.4x never used to transmit the data correctly although it worked fine with SDM. The Pentax 1.7x does.
03-13-2010, 01:08 PM   #3
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As you know, very few TCs work with SDM, the Tammy 1.4x MC4 Pz being an exception that mostly works. If that is the TC you have that transmits the true (lens x 1.4) FL then its the first one I have seen or heard of that does so. Maybe I should ask what camera you are using with it? Your Quantaray 2x works exactly as I would expect it to on a K20D.
03-13-2010, 04:26 PM   #4
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Sorry I mispoke on the Tamron. It doesn't transmit correct aperture info. But everything else works fine. Yes it's a K20D.

03-13-2010, 04:28 PM   #5
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This has always been a big issue with teleconverters on pentax.

My sigma TC feeds data straight through, so no aperture and focal length correction. this makes SR not as effective, and on the K10D screws up exposure due to the issues on metering with the K10D and K20D.

the only TC I know that corrects for aperture is the SMC-F 1.7x AF TC, but of coourse there is no power contacts for SDM or lens data fed throough
03-13-2010, 04:36 PM   #6
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OK so that's how these go. I'd never owned a 2x one with all the contacts and sort of assumed that SDM would work like the Tamron version does. Too bad but with a little EV comp, it takes fine pictures. Sharper than I expected actually.
03-13-2010, 04:41 PM   #7
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QuoteOriginally posted by Lowell Goudge Quote

My sigma TC feeds data straight through, so no aperture and focal length correction. this makes SR not as effective, and on the K10D screws up exposure due to the issues on metering with the K10D and K20D.
That's the only thing that annoys me with the Sigma teleconverters on my 70-200mm and 100-300mm. The combination would be about perfect otherwise.
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