70-200 2.8L IS will not AF >F5.6 ?

I keep hearing people said the Canon Autofocus will only work below F5.6, I'm a

bit confused...does that mean if I set the f-stop of my 70-200 to F8 or F11

then the Autofocus accuracy is pretty much gone? I should stick with using

F2.8~F5.6 for Autofocus to work properly right? by the way I'm using it on the

Canon 30D.

 

I also heard the Canon 30D will activate the special AF sensor when it detected

faster lenses >F2.8, so in this case....if I stop down my 50 1.4 lens to F5.6,

does that mean those 'special sensors' will be turned off automatically? LOL

No fret bro. All exposure and AF operations commence with the lens wide open.

I think you has already answer your qestion "I'm using it" so i gues you notice that its work as fine above 5.6 as it works At 2.8

<p>

special autofocus sensor DO work with all lenses wich the bigger aperture is 2.8 and its doesnt matter wich aperture u use that what really matter is the biggest avalible aperture of any lens<p>

regards <p>

jan

One of the great advances in photography was the METERING WIDE OPEN feature. Prior to that one had to stop down before taking the picture and use a hand-held meter OR meter with the lens stopped down.

 

Ain't technology great?

Ben,

 

The camrera and lens AF's wide open. The limitation you are refering to is if you have a lens with greater than a 5.6 MINIMUM apeture or a combo of lens and extender (1.4x or 2x) that drives the minimum appeture greater than 5.6. This means if you have a cheapo 800mm f/11 lens, AF will not work, or if you put a 2x extender on a 100-400L 4-5.6, AF will not work properly if at all.

 

2nd question, yes, the 30D and 20D have the precision AF for f/2.8 and faster lenses. I can tell the differnce when comparing my 20D and rebelXT with my 50/1.4, 24-70/2.8 and 16-35/2.8.

 

Mark

Canon Pro bodies EOS-1, EOS 1V, 1D, 1DS, 1D Mark II, 1DS Mark II. 1D mark II N, will all AutoFocus down to F8. All other Canon consumer bodies will only AF down to F5.6.

The lens stops down from maximum aperture to the shooting aperture just after you hit the shutter button, but before the shutter opens to take the photo. As long as the maximum aperture of the lens is not smaller than F5.6, AF works fine, and is uneffected by the aperture set for taking the photo since AF occurs before the shooting aperture is actually set.

thanks for all the great answers....learn something everyday ;-)