7D Mk II - overexposure with 2x TCs

Keith R wrote in post #17279805
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.

You'll fine Canon's fine print is full of disclaimers about that you should only use the camera with Canon's original accessories and lenses, or malfunction or even damage may occur. Should that happen, Canon rejects all responsibility for other manufacturers products not working with genuine Canon stuff. Canon reserves their right to make changes to their specifications at any time, without notice, and sometimes that even makes their own discontinued accessories not work with their new cameras. Or needing special attention, like not being able to focus with anything but the center point even with an f/2.8 lens.

So I'd say you could even live on the moon, but Canon have their back pretty well covered in cases like these.

Anders, it's probably best to leave discussions about the application of UK law to those of us who make their living in the application of UK law.

A company can have all the "fine print" it can muster, but that doesn't absolve it of its legal obligation to provide merchandise which works in a way which the average user would consider to be within "reasonable expecatations".

The fact that the camera is not responding properly to exposure information in a way which its immediate predecessors did, regardless of which manufacturer makes the lens in question, cannot logically be considered to be a problem with the lens (especially when the lenses work perfectly "naked" and with 1.4x TCs): ergo, it's a camera issue. And again, if Canon has deliberately caused this to happen in order to "discourage" the use of third party lenses, that's close to being an anti-competition restrictive practice.

But because that's not what will be happening, we're back to it being a "bug" with the camera.

And none of this is relevant to the point of this thread anyway.

Can we stick to information-gathering, please?

Yes, sorry for the diversion, Keith. I had a follow up question, so I tried to send you a message (to keep it out of the thread), but that seems not to be possible.
However, I think it's still of interest to those affected if they really should take this to Canon or Sigma (or other third-party lens manufacturer)? The way I see it, Canon launches a camera, then third party manufacturers reverse-engineer Canon's interfaces and make lenses that fits. Occasionally, Canon make changes to the interface, or implement parts of it that's been defined from the beginning, but not used previously, and then these who manufacture based on breaking the code used by Canon fail, until they've been able to drill into the new code. This has happened before, and has been resolved by updates by the third party manufacturers when possible.

EF 300mm f/4 L IS for the tests at f/8 with a 2X converter. 70-200 f/2.8L II for the tests at f/5.6 with the Kenko 2X. Did not test with the Sigma 50-150 f/2.8, had I known this thread would pop up, I would have just to have some info using a 3rd party lens. Was more interested in the 70-200 since I use that when trying to travel light and just taking 1.4X and 2X converters along.

Interesting. That was not my experience with the Kenko, which otherwise was fine on the other central group AF points on the 7D2. I would speculate that there are different parts of the command protocol that these 3rd party converter manufacturers choose to implement or not implement, or alter, as the case may be.

I also suspect that Canon has more than one AF algorithm depending on whether you mount a 3rd party lens, a Canon non-L series lens ( EF-S or other ), and an L series lens, especially the newer ones. Canon knows their own focus motors accelerations and non-linearities better than anyone else; they could easily use lookup tables for some high end lenses.

I am not seeing it with my Sigma 70-200 plus Sigma 2(x) teleconverter. Did some random shots here in my office shooting at a 44"x60" Electrical construction drawing. Camera sitting on tripod so both shots had identical location.

Perhaps the newest batch of camera's [got mine last night from Adorama] have had better QA/QC