Canon 50mm 1.4 focus issues

billythek wrote:

Ah! So you use AI servo. The story becomes more interesting.

AI servo is not great on the 5D2, but can work OK with the center point, especially if you are not trying to track something moving extremely fast, and you have good light.

Back-button AF on the 5D2 is a little different than with the 5D3 that I'm using now, and I forget all the nuances of the menu settings on the 5D2. The video I pointed you to by Rudy Winston was done back in those days, though, so he should be able to cover the settings.

Anyway, you need to lock focus somehow if you recompose while using AI servo, otherwise the camera will just continue to focus using the AF point where you move it to. So maybe you can go into some details about how you go about doing that, since there are several possible ways.

Yup, good point, the point of AI servo is usually that it continues focusing as you shoot to track moving things that stay under the focus points. In this situation standard focus and recompose will not achieve the right focus, in the sample you show it will refocus on the space between the babies. It seems you are not using the right mode for the intended purpose.

Also, maybe you can give details on how you select the center point for focusing, and if you use AF point auto expansion.

Any other relevant AF menu settings would be good to know, as well. What are CF III-3, CF III-7, CF IV-1, CF IV-2 set to? Do you have CF III-8 set to something other than disable?

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- Bill