Lens maximum aperture and AF sensitivity

GTG

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Was reading through one of my cameras manuals and I kinda knew that X type focus points don't work with all aperture lenses.

But I am shocked that unless I am reading it wrongly my canon f4 L lens turns all the X types points into horizontal only.

Gutted to say the least but I should have researched this more I guess.

It says with f2.8 AND faster lenses : all X type.

with lenses whose maximum aperture is larger than f/4 : centre point only X type.

larger than f5.6 ALL horizontal only.

So I can only assume my f4 L lens has no X type at all because it is not larger than f4 so does not even qualify for a centre X type AF point ?

It is meant to be a pro body 1d mk3 and pro L lens so this is gutting really that I have to buy f2.8
 
Have you actually found any focusing issues or just reading the manual?
 
Have you actually found any focusing issues or just reading the manual?

No issues yet but plan to move into rally photography and I figure I will probably be wanting the all X type AF rather than none.

I'm reading the manual because its raining for 3 days non stop. And I mean non stop
 
No issues yet but plan to move into rally photography and I figure I will probably be wanting the all X type AF rather than none.

...

Pro photography requires pro lenses, in the case of rally photography, I'd suggest a 70-200 as a start, and a 16-35 later, both 2.8

The 17-40 is really a landscape lens (and that's pushing it - to be honest, I have little time for that particular L)

And the answer to your actual question, you assumed incorrectly, you get the centre x type at f4, it's 'smaller than f4' that you lose that.
 
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No issues yet but plan to move into rally photography and I figure I will probably be wanting the all X type AF rather than none.

I'm reading the manual because its raining for 3 days non stop. And I mean non stop

I wouldn't worry too much with rallying. One big advantage of motor racing vs. other tricky AF subjects (bats at night etc. :) ) is that your targets are big, move in a fairly predictable manner and are usually covered in big contrasty decals. Number plates on rally cars are handy focusing targets as well. I haven't used your camera before but I've used some very ordinary Nikon DSLR's and lenses for rallies and never had any major issues. Once it gets dark, maybe you'll encounter the odd problem but most UK rallying now is 90% daylight.
 
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I believe the 7dmk2 are f5.6....just in case that tempts you.
 
I believe the 7dmk2 are f5.6....just in case that tempts you.

Have too many. 1d mk3, 7d, 6d, d300, d90, Fuji x100.

Sold d700, d7000, 550d, d5500, 40d.

I want a 7d mk2 and will probably try to swap my 6d for a very good example some day.
 
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