7D AF in AI SERVO (photos included)

Started Feb 4, 2013 | Discussions thread
Orange88 Regular Member • Posts: 286
Re: 7D AF in AI SERVO (photos included)

Ondrej Zeman wrote:

A lot has been written about the AF of 7D. Some say it is brilliant, some find it faulty. Unfortunately I have to lean towards the second group. Perhaps it is due to camera/lens/user error or maybe simply my expectations are just too high? Look at the sequence of following images:

ht

(Shot in RAW and converted to JPG without any adjustments, used Canon 135/f2 L lens)
I set the camera to 1/1000, ISO 100, f2.0, AI SERVO, central AF point selected, sequence shooting. The car was travelling 50 km/h. Out of these 25 photos, I would consider 7 photos to be in focus, 18 out of focus.

It would seem like the camera/lens is slightly backfocusing, but why are some of the photos in focus? I tried experimenting with Spot AF and AF Expansion as well, but in both modes the results were even worse.

Could it be faulty lens? I get kinda the same results with Canon EF 200mm f/2.8 L II USM. Faulty camera? Maybe? User error? What am I doing wrong?

Some might say that the situation is extreme - well not really for me, as I shoot a lot of fast moving cars in lack of light and altough I don't shoot as low as f2 but very often at f2.8. If I knew I could trust the AF, I wouldn't mind shooting at f2.
Any tips welcomed.

How far away was the car? It looked to me like the windshield and driver were in focus but the grill of the car was slightly out of focus. Maybe you have a depth of field problem? At a distance of 25 meters the focus plane is only 1.2 meters in front of the focus point. As the car gets closer it should be even more difficult to get it entirely in focus at F2.0, right?

 Orange88's gear list:Orange88's gear list
Canon EOS 7D Canon EOS 6D Canon EOS Rebel SL1 Canon EF-S 17-55mm f/2.8 IS USM Canon EF 70-200mm f/2.8L IS II USM +4 more
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