Which TC with 70-200 f4 L?

As title really... I'm about to buy a 70-200mm f4 L and wanted to get a TC to go with it but I'm wondering whether there's a difference in IQ or functionality between the Canon and Sigma (or other 3rd party TCs), are there any bargain gems out there or is the canon the way to go?

Also Ive read the 1.4x i well matched to this lens... what about the 2x?

Yes, get the 1.4x (I'd recommend Kenko pro or Tamron pro, they're the same thing with a different case).

The 2x will stop your autofocus from working on the 30D+70-200/4. But if you really want 2x, you can stack two 1.4x converters and that works though AF does hunts a bit.

At 2x200=400mm you really need the IS or a tripod. Or very bright light.

My experience is that the Canon ones seem to work better than Sigma (in focussing speed).

I don't know about the IQ from Sigma, but with care, the Canon 1.4TC can give superb results

Thanks for the replies

Anyone else have experience withe the Kenko pro 1.4TC?

Much as I'd like a nice white genuine one... £130 saving over the canon (nearly half the price) is not to be sniffed at if they do the same job

I have both the Canon 1.4 and the Kenko pro 1.4 and IMO there is very little to choose between them in terms of IQ. I also have the 70-200 f4 and the Kenko works fine.
I bought my Kenko Pro 1.4 from HK for £55 + postage of around £20.

I took these with a 30D / 70-200 f/2.8 / Kenko Pro 1.4xTC a few years ago (back when I first started out)

Thanks Roy... looks like theyve gone up a bit now (£99 + £10 postage) but still looks a bargain compared to £288 for the Canon!

Early on in my experiences with Canon dSLR, I did testing to compare Canon 1.4x-II and Kenko 1.4x DG with the 70-200 f/4L using targets rather than real life shooting. Canon has slight edge in Center, Kenko has light edge at Edge. Kenko is a better price-performance product, and it fits a wider variety of lenses...it just isn't off white and looking like an integral part of an L telephoto.

here are a couple with my 70-200f4IS and kenko 1.4tc. I love using this combo at the zoo.

outdoors

I have both tc's. The 1.4 is great for the 70-200.