Only those who have used Third party 1.4x TCs

[burstintoflame81]

I have a question. I know that most Teleconverters say they won't AF on lenses that are not f4 or wider ( for a 1.4x ) and f2.8 or Wider for (2x ). I was just wondering if people have had their lenses AF with a 1.4x that wasn't f/4? I know that a lot of times the specs are understated to save from complaints. I have a Canon 70-300 f4-f5.6 IS USM. I can put 32mm worth of extension tubes ( a 20 and a 12 kenko ) and still have AF work. I am of course talking about outdoors daytime shooting. Nothing really dark or super cloudy etc.

My reason for asking is I would rather get a 1.4x if I can AF, but if I am going to use a tripod either way I would go with a 2x or 3x instead. Thanks for your help everyone.

 

[fokker]

Sort of depends on the body you're using - the 1dmk3 can AF at f/8 on the centre point...

 

[burstintoflame81]

Good point. I should have specified that. I am using a Canon T1i. So I am sure its not the most sensitive AF system.