I just noticed that when using a 100mm Macro f2.8L on my 7D, if I start the focusing either from zero or infinity, it seems that AF is impossible with my 7D (it tries to AF but to no avail). My workaround is to turn the focus ring to approximate the focus on my subject, I press the shutter button halfway and the AF locks on. I don't have to start from zero or infinity - I would just make the scene totally out of focus, the 7D cannot autofocus all the way.
With the 5D mk3, the lens focuses as it should (searching for the right focus and then locks on the subject) even if I start from zero or infinity.
I don't know if this is how the lens works for the type of body it is on (FF or APS-C). Has anyone here have a 7D and a 100mm macro f2.8L and experienced the same thing (or differently)? Is there an explanation for this phenomenon?
I am loving this lens on the 5D3. With the 7D I will just add another step when focusing - if this is normal.