Canon TC 1.4x, is there a difference?

Hi Persian
I can think of one reason to consider using the 10D with long lenses, its called the crop factor (or whatever you like to call it)

10 D 1.6 factor times 400mm = 640

1 D 1.3 times 400mm = 520

I frequently swap bodies if i need more reach (1 D mk2 & D 60 )

also if i want the widest with my 14mm f2.8 I choose the 1 Dmk2

I use 100 to 400 L & 1.4 mk2 extender works fine on 1D2

Just to prove a point i have just put the 1.4 ex on my 100 to 400, set at the 400mm end hand held and photographed this screen believe it or not the shutter speed was 1/15th at f5.6 should not really be sharp but just look.
Cheers
Martin

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That's IS for ya. I want to buy a lens with IS next, that is why it is the 300 or 100-400.
I also use the 10D when I need more zoom. I notice that with good USM like my 70-200 it focuses fast enough for motorsport or any other sport.

Is the AF of the 100-400 as good as the 70-200? better? worse? BTW how does the IS of the 100-400 compare to the 300?

I want it to AF on both bodies so I will either get the 300 or the 100-400 and tape the contacts. But right now a lens is far away(mid-late summer), I'm not really concerend about that ATM.

I'm afraid the AF of the 100-400mm is substantially slower than the 70-200mm f/2.8 IS anyway,. and I suspect this will be true of the non IS 70-200mm as well. It's no slouch,. the 100-400mm is still and "L" after all,. but I beleive it has been established that the 70-200mm f/2.8 (IS) is Canon's fastest focusing zoom lens. So no,. your 100-400mm will not be able to keep up.

Also,. the 100-400mm larger AF weekness,. is focus tracking where small objects are concerend, it's not such a huge issue with a frame filling large subject,. but for birds in flight at a distance,. the lens shows this weakness.

And this is again where more compormise comes in,. as this focus tracking is a place where the 400mm prime absolutely excels!

CDS: http://www.iespell.com​/

It's free!

Not using ie

CDS there is one for FF too...............lol
Unless you are using some complicated redhat/Linux thing.........

No one asnwered my other question. Is the Canon one better then the Sigma, Tamron or whatever else brand there is?

Mmmmm....of course it is. Nothing is better than Canon glass.