08-22-2016, 12:35 PM
I can't verify in any way the AF behavior of the 17-55mm f2.8 IS USM in comparison to the EF 50mm f1.4 on your APS-C cameras, so I can't comment on what is causing what.
The 24-1-5mm f4 is an f4 lens, so it surely can't take advantage of f2.8 center cross type AF points.
Not sure where the flash talk fits in?
The 24-1-5mm f4 is an f4 lens, so it surely can't take advantage of f2.8 center cross type AF points.
Not sure where the flash talk fits in?