[Guest]

Well,

the base distance in PD is determened by prism angle. Yes the diferent prism angle in PD requires diferent AF sensor by this has never been an issue for middle and pro range SLR. I still puseling what is advantafe of such system.

The only one that I can see is lowering the cost and reduce machanical requirements.

 

In order for the camera to take a picture or make a movie, the mirror must be up (unless it's the Sony SLT system, with the permanent mirror). During that time, "normal" PD AF does not work. So, it does not allow for continuous AF in movies, and even when taking pictures, if you shoot series, as long as the mirror is up, AF cannot track. So even for photography, when continuous tracking is desired, such a new system can provide benefits. 

In theory at least, the new system now has many many more AF sensors compared to the traditional PD AF, which is limited to selected points determined by where the AF sensors are located.