Canon ef 400 f2.8lis

[chris954]

Has anybody used one of these for motorsport with a canon ef 2x extender, preferebly the mkii version (extender) i’m considering wether to get one or a 500 f4 I just cant decide which would be more versatile. In particular how much does the extender affect focus speed and accuracy.

 

[Canon Bob]

As far as the spec's go you would be operating under the following conditions;

The AF speed of the combination would be 25% of the lens' speed without the extender.
The accurracy would change from within 1/3 DoF to within DoF (assuming the availlability of an f/2.8 focus point)

In practise, you might not see the degraded operation as things are still quite fast and don't really challenge the AF once the subject has been acquired.

Bob