extender query

[Flying giraffe]

I have just bought a 1.4x canon extender to try with my 100-400, now I know this won't af on my 7D, but my question is, why can I af through live view? Surely if can't focus, it can't focus, thanks in advance.

 

[Canon Bob]

Liveview focus should work fine as it uses contrast detection.

Bob

 

[Flying giraffe]

Thanks, I've learnt something today, cheers

 

[modchild]

Have you tried using AF in bright light with the TC on. I recently bought a Kenko Pro300 DGX 1.4x TC and the 100-400 L retains AF with it on. Even in poor light AF still works, just not as fast. I read a review of this TC on the web and it said about working with the 100-400 L which is why I went for that model. I can also use it on my 24-105 f4 L, my 100 f2.8 L macro, my 70-200 f4 L (now replaced with a 2.8 IS L) and my 50 f1.8 and retains AF on all of them, the only one that ends up manual focus is my Sigma 150-500 OS f5-6.3, which comes out as f9 with the TC on. All the above works on both my 7D and 5D2, so I'm very happy with the TC, especially as it only cost £125 or so.

 

[Flying giraffe]

havent tried it in good light yet, hope to at the weekend, i did google it and it seems it doesnt unless you tape the pins though

 

[admirable]

The danger in flaffing about with it is the constant use of the motor hunting and attaining focus burns out the motor in the lens.

 

[Flying giraffe]

The danger in flaffing about with it is the constant use of the motor hunting and attaining focus burns out the motor in the lens.

hadnt even thought of that, ill give it a go this weekend, will it hunt less in bright conditions?

 

[MadWoman]

I understand the Canon TC does need it's pins taped, but I have a Kenko and use it regularly in my 100-400. It is a bit slower, than without and sometimes just loses focus, but rarely hunts and will focus in quite poor light as well. I have missed the odd shot through it suddenly defocussing, but have gained many more than I have lost!