Originally posted by jogiba
Thats exactly the PK-NEX adapter that i use on my Nex 5n. It does have some limitations, but its not bad.
I just tried mounting that adapter to a Pentax FA50 f1.4. If you rotate the adapter ring with the Lock to Open markings, all the way to the open position, you will see by looking into the lens, that the lens is fully open to F1.4. If you set the aperture ring on the FA50f1.4 to f8, and then rotate the adapter ring to "lock", the lens will partially shut down the diaphragm to the f8 position. So in that way, you can adjust the FAlens and PK adapter to any specific aperture.
But take a modern DA lens without any aperture ring. If you install the PK adapter on such a lens, you can easily set it all the way OPEN to the wide open lens aperture, whatever that is. But going in the "LOCKED" direction, you will see the diaphragm start to close as the adapter ring is shut down, but you will not know exactly what aperture (smaller than wide open) that you are at.
So the PK-NEX adapter works best on a Pentax lens with a manual aperture ring, still has some aperture functionality on a Pentax FA lens, but will not tell the operator what aperture number you are at on a modern DA lens. You can still reduce the aperture wtih the LOCK/OPEN ring, but you won't know what numerical f-stop you are at.
@kenafein
I didn't buy the Nex 6 for similar reasons. I think if Sony makes the Nex FF as fully firmware featured as they can so as to out-strip the D600, they will have a winner on their hands. If they cripple the Nex FF firmware so it won't undermine the A99, then it will be less successful.
I carry around my 5n a lot, but its a good example of unnecessary crippling in my mind. Take the ABM mode, anti-blur motion, where it stacks up to 6 images to remove blur. Its an amazing piece of firmware, except they crippled it against the same mode in their Alpha cameras. You can't adjust the parameters in the Nex ABM mode, where you can in Apha line(so i've been told). Also, Nex ABM is restricted to jpeg output, don't know about the Alpha line. I won't pay $1700 to $2000 for a crippled Nex FF camera, but i'd be tempted if they make it all it can be.
Sony has the opportunity to build a stellar Nex FF, and they need a winner like it can be. But will they let the designers have a free hand - hope so.