Anyone know definitively why PD AF points on full frame cameras are all bunched in the middle? It's one feature that I haven't really seen improved generation after generation of DSLRs.
I suspect it's got something to do with the sub-mirror size limitations that directs light to the AF system but can't really find any confirmation.
But even Sony's SLT's don't seem to have a wider spread of AF points although on the A99 there appears to be some non-selectable on-sensor PD-AF points at the periphery.
Perhaps PDAF points near the peripheral aren't accurate enough or light fall off is too great at the edge for reliable AF?
Maybe there are FF cameras with wide AF points.. If so can someone direct me to it.