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03-18-2014, 06:15 PM   #1
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New 1.4 rear converter and Sigma 70-200 (2.8) ?

Will the new Pentax rear converter (1.4) work with the Sigma 70-200 (2.8) HSM zoom ?

I now have nice new K- 3 body and hope so...

03-18-2014, 07:38 PM   #2
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I don't want to sound blunt but wouldn't it be more logical to save for the extra money needed for an used DA* 300mm F4 instead? The TC will degrade the image quality, especially at the extremes of the zoom, while you would instead get better image quality with with the 300mm.
03-19-2014, 06:44 AM   #3
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QuoteOriginally posted by tmacdon Quote
Will the new Pentax rear converter (1.4) work with the Sigma 70-200 (2.8) HSM zoom ?

I now have nice new K- 3 body and hope so...
Got a reply from Sigma UK

The question posed was when will Sigma 'fix' their HSM lens to function correctly on the converter.

"Japan have stated that your Sigma lenses are not compatible with this converter and unfortunately it is not possible to make them function. They have stated it is something they may look into producing in the future but there are no guarantees."

i.e No HSM lens will function correctly with the converter and Sigma have no plans to fix it.
03-19-2014, 11:00 AM   #4
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QuoteOriginally posted by awaldram Quote
Got a reply from Sigma UK

The question posed was when will Sigma 'fix' their HSM lens to function correctly on the converter.

"Japan have stated that your Sigma lenses are not compatible with this converter and unfortunately it is not possible to make them function. They have stated it is something they may look into producing in the future but there are no guarantees."

i.e No HSM lens will function correctly with the converter and Sigma have no plans to fix it.
Does anybody know yet whether the firmware on the Pentax TC contains a list of lenses it uses when adjusting the FL and aperture, or does it just do the math?

Also, I take it the AF doesn't function at all on the Sigma HSM lenses. Is this a result of Sigma doing imperfect reverse engineering on the protocols, or because Sigma lenses are absent from something like a "whitelist" on the Pentax TC?

03-19-2014, 03:09 PM   #5
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QuoteOriginally posted by DSims Quote
Does anybody know yet whether the firmware on the Pentax TC contains a list of lenses it uses when adjusting the FL and aperture, or does it just do the math?

Also, I take it the AF doesn't function at all on the Sigma HSM lenses. Is this a result of Sigma doing imperfect reverse engineering on the protocols, or because Sigma lenses are absent from something like a "whitelist" on the Pentax TC?
The 150-500 hsm focuses but doesn't translate the fstops and focal length. I would think that the different implementations of the reverse engineered protocols are the problem.
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