Obnoxious Focus Problem -- Help me!

[branden]

Hi

Here's the best way to summarize this situation:
When shooting events, I usually use two bodies, a 5D MkII and a Rebel T3, and two lenses, a 24L MkII and a 135L. I swap the lenses back and forth between the bodies as needed.

The 135L consistently focuses correctly on both bodies.
The 24L only consistently focuses correctly on the 5D MkII; on the T3, it usually ends of focusing too close, by as much as a foot or two.

This issue comes into play most when in poor lighting (even using the flash), but it seems to happen at all subject distances.

I'm pretty sure something needs to be calibrated by Canon (everything's under warranty), but I'm not sure what. Any help?

Thanks

 

[neuroanatomist]

I'm pretty sure something needs to be calibrated by Canon (everything's under warranty), but I'm not sure what. Any help?

It could be either the 24L or the T3 - in the end, you might need to send both, or perhaps the T3 and both lenses, to Canon for adjustment.

You might try sending the 24L first, and if they adjust that and it works on your T3 but not on the 5DII, you can AF microadjust the lens on the 5DII. If you send the T3 and they adjust that, it might result in the 135L no longer focusing correctly on the T3. Issues like this are why I'll never get a body that lacks AF Microadjustment (and issues like this were why Canon Professional Services was born - pros used to send in their entire gear collection to be calibrated together).

In fact, it might be best to call up Canon support and ask what they recommend...