Now, I'm sure somebody will correct me very quickly if I am wrong but...
The A7R does not have an optical low-pass filter. This means it struggles with AF but gets cleaner data from the sensor. Doesn't the low pass filter blur the image slightly?
So yes, you get cleaner images from a sensor without a low pass filter but it also has it's drawbacks - i.e. the AF sucks.
Autofocus and the low pass filter are completely unrelated. Phase Detect autofocus was not put on the A7R to differentiate between the two models, it's pretty much just a marketing decision.
I'm guessing that this is also exactly the same sensor being put in the D800, and for the sake of using the same manufacturing process, and not splitting the lines, they just stuck the chip in without changes to the silicone.
actually, the Sony Alpha 7R has special micro lens design, and thus, Sony could not put the Phase Detect AF on the sensor, not just a minor marketing decision.
and the D800E sensor is not the same sensor as the one in the 7R.
the Alpha 7R sensor is more advanced new design,and the D800E sensor has Nikon original micro lens design.
anyway, the point here is the 7R sensor has different micro lens design from that of the Alpha 7 sensor and that is why it does not get the PDAF on the sensor.
the real reason Sony needed that odd micro lens design for that particular sensor was that the mount diameter of the E mount was a bit too narrow for FF sensor since it was originally design for APS-C sensor.
just the mount can take FF sensor does not mean it fully optimizes it or even fully utilizes it. alpha 7R has some corner image quality issues with many many lenses I have used with an A7R(I tested the A7R a few times at Sony plaza).
Again, I am quite sure it was not a marketing decision alone but the corner IQ issue was the main reason why Sony used that unique special micro lens design for that specific 36 mp sensor used in the 7R(typical R buyers are more obsessed with corner IQ) even at the big cost of losing fast PDAF.
I think landscape type of D-SLRs are literally killed by that Sony A7R (the sudden 20 percent drop of the D800E resale value tells that), however , event high ISO type of D-SLRs may be able to survive for a few more years(until sony or fuji comes up with serious FF mirrorless system with great AF design).
So it is Nikon that is really doomed after the A7R not Canon.
Personally, I will replace my D800E with this new Sony A7R , but I will keep my EOS6D for lowlight event work.
PS. Sony stock hits hard here in Japan after its announcement of its Q3 financial result, and some of Sony stockholders asking Sony to quit all digital still camera and consumer video camera business.