Sigma 500mm F4.5 + Canon EX 1.4 II + EOS 5D mk3 - focus problems

Started Mar 23, 2016 | Questions thread
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kallipk
kallipk New Member • Posts: 6
Sigma 500mm F4.5 + Canon EX 1.4 II + EOS 5D mk3 - focus problems

Got myself recently a used Sigma 500mm F4.5 DG EX HSM to get some more reach, but i have some problems with extenders.

In earlier times it was often reported that this lens should only focus on 1D bodies using converters so i thought it should not have any problems with 5D mk3 that has same level AF system. But still it seems i have some problems locking down on AF spot.

So at the moment i have tried with canon II extenders both 1.4X and 2X with and without taping the pins. It seems that the camera really struggles to lock down on AF spot with any of the extenders mentioned above attached.

Without taping the pins on extender (1.4X) - the lens is reported to camera as 6.3 lens and it tries to focus, but at most of the cases it never reaches focus. It just hunts rapidly around near focus area, but does not lock down on spot. If i tape the pins the hunting is just a lot faster (I guess the extender software slows down the lens AF to help camera finding focus points), but still no AF lock.

With the 2X extender it does not focus without taping the pins (well that is obvious as it is F9 lens then) but with taping the pins same story - hunting around near focus but not hitting the focus spot.

Have anyone experienced similar thing? I have heard that Kenko Pro 300 series extenders should be okay with this lens, but i can't find any on my local dealers so for now i am stuck with my canon extenders.

I also started wondering if there could be some dust in extenders of in my camera, but when attached to EF 300 F4 IS, AF seems to work okay even with 2X extender (making the lens 600mm F8 effectively). So the camera and extenders should be okay in that sense.

But in a positive side - the 500F4.5 without extenders is already a real beast. IQ is far-far superior to EF 300 +1.4 EXII

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