7D Mk II - overexposure with 2x TCs

I believe they mean that the 50-500 only offers Manual Focus if any of the TCs are mounted.
http://www.sigmaphoto.​com/teleconverter-compatibility

Snydremark wrote in post #17278336
I believe they mean that the 50-500 only offers Manual Focus if any of the TCs are mounted.
http://www.sigmaphoto.​com/teleconverter-compatibility

His response makes sense in light of the link you posted. The odd thing is that the XSi I am using now does autofocus with the TC in bright light. Perhaps it isn't guaranteed.

Capn Jack wrote in post #17278392
=Cap'n Jack;17278392]His response makes sense in light of the link you posted. The odd thing is that the XSi I am using now does autofocus with the TC in bright light. Perhaps it isn't guaranteed.

That's basically it. The manufacturers will state that AF isn't supported; but, by using a non-reporting TC or taping a couple of pins, people will get AF to work, after a fashion.

OK guys, can we stay on topic, please? There's no issue with 1.4x TCs in the scenario this thread is about.

Keith R wrote in post #17277253
Nobody else shooting with a 7D Mk II, 2x TC and third party lenses, then?

I'm shooting with a third party TC (Kenko Pro DGx) on a Canon lens... Sample image below...

IMAGE LINK: https://flic.kr/p/pL4Q​mz

Capn Jack wrote in post #17278323
=Cap'n Jack;17278323]No, but I got this response from Sigma today when I asked about using a 50-500 IS and my sigma 1.4 teleconvertor :

Hello Jack,
No it will not, the converter will prevent it.
Yours Truly,
Paul Pizzano
The Sigma Corp. of America


I'm still trying to understand that...

What was the exact question you asked?

I seem to be having the same problem.
7D Mark II
Sigma 120-300 f2.8 Sport
Sigma 2x teleconverter

With teleconverter

airbutchie wrote in post #17279321
I'm shooting with a third party TC (Kenko Pro DGx) on a Canon lens...

Thanks.

It's third party lenses that I'm actually trying to get a handle on, but good to see that you're not affected.

Christopherm wrote in post #17279606
I seem to be having the same problem.

Yep, that's exactly what I'm seeing, Christopher.

I've already pushed this Canon (UK's) way, but it would be really helpful if someone with (say) a Tokina or Tamron 70-200mm f/2.8 and a 2x on a 7D Mk II could confirm the behaviour - then Canon won't be able to push responsibility onto Sigma...

Did you push it Sigma's way?
Canon is in no way obligated to make it's cameras compatible with aftermarket products.

Example:
"Sigma has posted a statement on its website regarding incompatibilities between its lenses and the Nikon Df. As with the D5300, both autofocus and image stabilisation may not work correctly; however lenses without built-in focus motors are also affected when used on the Df. The company says it will provide free lens firmware updates to fix the issue, but this may not be possible with discontinued models."

http://www.dpreview.co​m …mpatibility-with-nikon-df

I think you will discover that all of the 2X converters that are overexposing by 2 f-stops do not report the correct aperture to the AF or metering system. They may report the correct aperture in the EXIF data.

I have a Kenko CA-F 2X Teleplus Pro 300 which behaves in exactly this fashion on both my 7D and a 7D2 that I recently evaluated. You must dial in -2 f-stops exposure compensation, the metering/exposure system thinks it is dealing with a lens that has a 2 f-stop max aperture greater than the lens+converter really has, which it is then subsequently stopping down to the the final aperture ( which isn't what is actually happening ). Hence the over exposure.

I note that a Canon 2X III used in the same situations reports the correct aperture to the metering/exposure system and does not need any compensation.

FWIW, the Kenko converter will focus with all 65 pts on the 7D2 at f/8 max real aperture. It will focus using the outer 10 pts on the 7D.

Waldemar Sikorski wrote in post #17279750
Did you push it Sigma's way?

Not yet - as I've clearly explained, I'm trying to establish whether only Sigma lenses are affected.

Guess you don't live in the UK, then. In the UK, "merchantable quality" is a legal right; and any product which does not function properly in "reasonably typical" usage circumstances - and working properly with aftermarket lenses (as the camera's predecessors all do) qualifies - would push very hard against that right.

Furthermore, for Canon knowingly to deliver a change which - it might argued - prevents reasonable use of third party lenses, could be construed as a "restrictive practice". Of course they haven't done this - it's just a bug - and now they know about it.

russbecker wrote in post #17279769
I think you will discover that all of the 2X converters that are overexposing by 2 f-stops do not report the correct aperture to the AF or metering system. They may report the correct aperture in the EXIF data.

Both of my 2x TCs report exposure data perfectly accurately when mounted (with the Sigma lenses) to my 7D and 70D bodies.

The converters haven't changed. It's the new body that's behaving differently.

Again: both of my converters work perfectly well, with the Sigma lenses, on my 7D.

But which lens?

Well, I can't speak for the Sigma 2X converters. I can tell you what happens with the Kenko, and what happens with the Canon 2X III ( which behaves as advertised).

I can also tell you that if I mount a lens with a f/2.8 max aperture with the Kenko 2X converter on my 7D, the AF performance becomes interesting. It will AF on all 19 pts, but the performance at the center point is problematic. If you think about it, you can see how this comes about. The Kenko 2X reports a final aperture of f/5.6 to the camera, but reports the max aperture as f/2.8. This causes the 7D to try to use its high precision f/2.8 cross point at the center with a lens that has a max aperture of f/5.6. The result is a bit erratic. If you use any other point on the 7D, it snaps into focus.

The same situation on the 7D2 gave similar results, the center AF pt behaves a bit erratically. The others are fine. To me, this is just part of trying to get more performance out of the camera system than it is specced for.

Thanks Russ - it's all useful input.

Could you let me know which lens(es) you're testing with? That's a big part of what I'm trying to nail down.

(Just as an aside, the 7D Mk II centre AF point works perfectly for me with a 2x and f/2.8 lens attached).