3) If you are totally desperate, like on a desert island and need to focus the suns rays through the lens to light a fire, then you may attach the 2x teleconverter. With the in-built teleconverter OFF, autofocus works slow but you can only use the centre focussing point. With the in-built teleconverter ON you are limited to the joys of manual focus.
To be truthful, a better method here is to take the 2x converter, place it gently on the ground so that it is bathed in lovely soft, evening light. Then paint your teeth red and smash it violently to pieces with a large baseball bat, cackling maniacally all the time at passers by. Go on do it, it will feel so good. Now before you think I have an issue against Canon 2x converters I don't! I hate ALL 2x teleconverters equally!!! I consider them a complete waste of space and money, it is always better to use a 1.4x teleconverter and crop. Of course that is just my view!
(Underscoring mine.)
Being a notorious user of TCs, I of course disagree with Mr. Rouse. On sharp base lenses, there's a significant increase in detail captured with a 2x over a 1.4x. On my 400 2.8 IS, the increase in captured detail goes up all the way to a 4x TC.
I hate the silly things. Not because the IQ is that bad. But my skills are not that good. I can tell the IQ drop on my lens. Even when I put on a 1.4 I have problems. It slows me down to a crawl. I use the 1.4 allot. On the 300 It does a good job. But when I put it on the 500 I have to slow down and put it on a tripod or bean bag and really concentrate. I am getting older and it is just a pain for me.
Beautiful shots all. But for me it is a vote against.
Just trying out this combo - Canon 5D MIII + 500 f4 IS + Canon 2x TC II, 1000 mm, f/8, ISO 1250, 1/250 sec, 475B/516 support, manual exposure in available light, center AF point AI servo, 3600 x 2400 crop resized to 1200x800.
- which I'm still checking on.
