Canon 1D Mark III autofocus



Sequence 1:

First I thought I would try the EF 135mm f/2.0L with 1.4x EX II extender in AI Servo with AF setting to ignore foreground obstacles and used ISO 3200 to give 1/1600th sec to minimise camera shake or subject movement causing unsharpness.

I used the AF-ON button to set focus whilst attempting to ensure the subject was on the center AF point to acquire focus

This whole sequence ended up the same - nicely in-focus advertisement banners in the background but out of focus players.

I am guessing the main problem here is that unless the player fully covers a AF point then the AF point selects the background.

This may be remedied with the new firmware upgrade.

Sequence 2:

Worked out how to get 100% of the sequence in focus - use manual focus with a $50 lens from Ebay, the Sigma 70-300mm f/4.5-5.6 for Olympus OM mount - here I have used ISO 6400 to cope with f/5.6 at 300mm:


the whole of this sequence was in focus BUT it required pre-focusing on a predicted zone of action.

Unlike the AF, there is no evidence of players going in and out of focus as with the current AF mechanism.

Sequence 3:

An advantage of the manual focus method is that even if the players fall out of the AF sensor ring, they still remain in focus:

and another example of manual focus:


BUT there is a big problem with manual focus - if the action quickly moves to a different zone, you will miss shots as manually acquiring new focus takes time.


I went back to the AF lens and had mixed results - much more reliable when the action was close and filled much of the central region, very unreliable when players at 60m as with sequence 1 above, presumably as dominant central AF point selects background or foreground in preference to the players.

A solution (assuming no improved algorithm from Canon) in this scenario would be to get closer to the action with a 300mm f/2.8 or even a f/4 lens so the players fill the central AF region more completely.