I bought A7R recently, moving from A900.
I was little complaining about the AF speed and the hunting. I was so frustrated I thought my camera was defective and was about to return for an exchange.
It failed to lock in low light (with or w/o AF light), it hunted in indoor with lots of window light, it even missed focus outdoor in broad daylight.
I googled and found that many people complained of the same while some said AF is quite ok, I found someone said it is better than D800. With these in mind I was almost sure that my unit was defective. So, I initialized my camera, packed and got an RMA from B&H.
Suddenly I thought why not test the camera with the 50 1.8 E mount lens and see if my lens is defective and also test the FE 55 with Nex6 to see if my camera is defective.
I again unpacked it, mounted the lens and to my disbelief, the A7R-FE55 started working just fine, it locked 100% time, AF was spot on to the extent that I cannot do better AF with MF and magnified view.
Finally I got it, it was the Face detection that was causing all these issues. Turn the FD off, AF locks with little hunting in low light(It is so low that I cannot frame the object through my A900 OVF), AF locks in backlit faces, I tried to turn the AF light off, no effect, it locks just fine. I turned the FD on, it started hunting again. Hunting means it racks the lens full length 2-3 times before it locks or just give up w/o locking.
I am not sure if this is normal in other A7R or if my unit is faulty. Forum members can confirm.
I posted this same article in DPR and Dyxum and some forum members observed the same as me.
I am with v 1.02 and FE 55 lens.