Tele converter focusing questions??

Hi,

I've tried to do a search and the more I read the more confused I'm becoming. So sorry if this has been asked before.

Recently my hubby gifted to me a Bower (fits canon multi-coated 4) 2x teleconverter, digital autofocus PRO DHDII. I have a canon EOS 650D body (I think known to most of you as a rebel T4i) and my lenses are a canon EFS 18-135mm IS STM, a canon EF 50mm and a canon EF 70-300mm IS USM.

So my questions are. Today I tried out the T.C for the first time with my 70-300mm lens (trying it out on birds) I couldn't auto focus, it was trying to but wouldn't actually get anything into focus, but a small number of times I could manually focus with great difficulty and a very very fine line to actually getting something into focus. I think my focusing was set to AI SERVO in auto focus mode. Why wouldn't it focus very well? are the lens or T.C not compatible (which I don't really think is the case, as I will show you an image for example).

Also I noticed I couldn't get an aperture any wider then an f10 (I was shooting in manual mode) , is this what I should expect to happen each time I use the T.C? Am I doing something wrong? I've wanted to begin to learn to use back button focusing, can I still do that with the T.C attached? I wanted to get a T.C for more reach and can't really afford a longer lens for quite some time. Will this T.C work with all my lenses? although I was more interested in using it with my 70-300mm lens for shot's of animals, birds....etc that I can't get real close to. Any extra info would also be helpful.

Here is an example of what I captured, my focusing slightly off and it took quite a bit to try and get it. Also all my EXIF info was attached to the image, so if the lens or T.C wasn't compatible this info or image should've worked?? So why am I having focusing trouble??

Thanks for your help.

TC will work with you lenses but after F8, the camera cannot auto focus and the only cameras that can AF at F8 are 1D series and 5D Mk3. Added a TC changes you aperture by up to 2 stops depending on which type either a 1.4 or 2x.

Your 70-300 is f5.6 on the wide end, adding a 2x teleconverter makes it a minimum of f11 (you lose 2 stops of aperture).

As a result you lose AF.

As said above, only 1D series body and 5D3 can AF at f8. Your 650D stops at f5.6.

Thank you both so much for such a quick reply. This I didn't know .... so now I get it ... that makes sense. Thanks a bunch.