AF with 1.4x tele MK III and 100-400 L MK II

[Labdoc]

Added a 1.4x tele-extender to my 100-400 L MK II and the autofocus won't work at all when looking through the viewfinder. Camera (70D) reports manual focus, no matter how I set the buttons on the lens. Switch to live view or movie mode and AF works fine. I borrowed a Kenko 1.4X PRO 300 Teleconverter and got opposite results. AF worked fine in the viewfinder, live view and movie mode reported "please attach lens to camera" and nothing worked. The lens works fine without the extender and the problem now is figuring out where the fault is and what needs to be fixed, the lens, tele-extender or the camera? I wrote CPS and am waiting for some guidance. Anyone have any ideas?

 

[candc]

Regular phase detect af on the 70d is limited to f/5.6 the combo you are trying to use is f/8 so it won't work.

 

[Harv]

I believe the 70D will only AF down to f/5.6 and when you add the 1.4x TC to the lens it becomes f/8. The Kenko does not report to the camera so it thinks the combo is still f/5.6 and performs AF.

 

[Labdoc]

I believe the 70D will only AF down to f/5.6 and when you add the 1.4x TC to the lens it becomes f/8. The Kenko does not report to the camera so it thinks the combo is still f/5.6 and performs AF.

But would it still work in live view and movie mode? If I get a 5D will it work?

 

[underbjerg]

It works on my 5D mark III, and it should also work on a 7D mark II.

 

[Valvebounce]

Hi Labdoc.
F8 will work on the 5DIII and 7DII, but you will be limited to the centre cross point or if you select 4 point expansion you will have horizontal detection on 2 and vertical detection on the other two points plus the centre cross point. With the 4 point expansion there is no manual selection of points and the cross cannot be moved about.
If you want all f8 focus points you will need a 1Dx II. Or maybe canon will turn on a few more f8 points on the 7D II and 5D III with a firmware update because we would like them and they are so nice! ;D ;D ;D ;D

Cheers, Graham.

It works on my 5D mark III, and it should also work on a 7D mark II.

 

[Labdoc]

Thanks for the replies. Looks like I have to either get a new camera or just use it in live view where it works fine. I just read about covering two of the len's electric contacts with tape where the camera would function as if no lens was attached, like the Kenko I tried, then it would AF in the viewfinder. Seems like an easy fix but I really don't want to start messing with my gear. Will probably order a 5D MK IV as soon as it's released.