Extenders & Extension Tubes...

Hello. I currently use the Canon 70-200 F/4L for shooting youth sports. I can not afford anything better at the moment.
If I am at the 3rd base side my 1st base shots are usually OOF- and vice versa. I was considering getting an extender.
From what I read the Kenko will work with the F/4. Are there any other ones? I see some cheap ones on ebay - has anyone tried those? What about the Canon 1.4, from what I read in the description it says it works with 2.8 or brighter, but some reviews said it will work with the F/4? I am so confused. Another thing is besides B&H I can't seem to find a Kenko... I have been checking ebay for weeks... they are all from hong kong. I did find one for $100 BIN but as I hit the button someone else did as well.

Moving on...

So, then I see extension tubes, what exactly are they? Will this work for me or should I go with the extender?

Any help is appreciated. Thanks.

Lots going on here.

To start, extenders are not going to help you with OOF shots. If anything they will make that worse because extenders make the AF system work much more slowly. If you are getting OOF shots you need to figure out why and fix that first.

a 1.4X TC makes all lenses 1 stop slower. a 2X TC makes all lenses 2 stops slower. Your camera cannot AF with anything slower than f/5.6, so you can use a 1.4X TC and retain AF. If you use a 2X TC you will lose AF.

Don't go cheap on a TC. You are using a quality lens, so don't stick some crap knockoff TC on it and get lousy IQ. The glass quality of a TC is at least as important as the glass quality of the lens. Get the Kenko pro on a budget and the Canon Extended 1.4X II otherwise. I have also heard that Sigma makes a good TC.

Extension tubes are for macro photography. They are absolutely not what you are looking for.

Thanks for the help.

I was thinking the reason my shots are OOF is because I am having a hard time seeing where I need to focus, I was thinking the extender will bring me closer and I will be able to see better to focus better. Am I wrong?

You are right about sticking junk glass on. I pretty much contridicted myself even asking because I am usually one to say the exact same thing when someone talks about putting junk glass on their nice camera.... so thank you for reminding me

Do you know about the difference in quality of the Canon and Kenko? The price difference is pretty steep. What about a Tamron? The tamron is pretty cheap in price, is it junk? I am really tired of looking for the kenko used so I was going to just bite it and order it new, so it's like $200 plus tax and shipping. I just found a used Canon (the white one to match my lens too) for $185.Should I grab that instead?

Few people have tried several TC's to give an opinion. As with most things, the Canon is probably a little better than the very good third party units at a ridiculously higher price.

If you are price sensitive just grab a quality Kenko, Tamron or Sigma TC. Make sure you are getting the highest level that that company makes (pro or whatever) and it will probably work well.