70-200mm f/2.8 + 1.4x, multiple focus points.

[Persian-Rice]

Since my stuff got stolen I sit here in my room and mess around with what is left or whatever is on loan till i get my stuff back.

I have read on more then five different sites that the 70-200 f/2.8 when used in combination with a 1.4x TC, will only focus using the center focus point. Now I am sitting here and trying different things, but this combination will focus with all the focus points on the 10D and it will also work in AFP selection as well.

What is going on?
I'm really confused.

[PacAce]

You heard wrong because, as you have already discovered from your trials, that simply isn't true. However, the 400 f/5.6 (and the 100-400) with the 1.4x on a 1DmkII will only focus with the center AF point. But that same combo won't even AF on a 10D (or a 20D).

[CyberDyneSystems]

On a "1" series Camera,. the single focus point operation kicks in above f/5.6,.. the same point at which the "non 1" cameras will lose autofocus alltogether.

ei:
Any lens/t-con combo with aperture of 5.6 or larger will operate normally.

Any lens t/con combo with an aperture f/5.7-f/8 will focus with only one focus point.

In practive however I have the the f/5.7 cut off point to me or a "suggestion" as I have had combos in the f/6.3 range that focus "normally" wiht multiple AF points. No idea why.

[Persian-Rice]

Ah OK thanks, even B&H writes that it wont work..........odd.

[PacAce]

OK, now I see. You are actually referring to the EF 70-200 non-IS version. Well, that lens is sort of an "anomaly" as far as Canon lenses is concerned. It even behaves weird when used with the ID series camera as well. A lot of people have complained about it's odd behavior when it comes to focusing. And, according to Chuck Westfall, that's just the nature of the beast.

[mbze430]

I always thought the 1-series will only center focus when it's equals to f/5.6

[CyberDyneSystems]

I always thought the 1-series will only center focus when it's equals to f/5.6

Smaller than 5.6... ;) Not Equal.

5.6 or larger and it will use all AF points.

[mbze430]

yeah, like he said.