There is a lot of excitement about the A9 speed of focus and its shooting frame rate, and rapid refresh of the 120 fps LED in the viewfinder. But that is an E mount camera from Sony. Hard to say at this point what -- if any -- improvements in the A9 would materialize in the A-mount cameras from Sony.
A couple of considerations in the A-mount offering...
- unlike the E-mount cameras with sensor-to-viewfinder EVF, the A-mount cameras rely on a half-silvered mirror to deflect some light upward to the eyepiece, while the rest of the light goes through the reflex mirror to the sensor -- but that means that 0.5EV of light is NOT reaching the sensor. Like any pellicle mirror camera, it loses some sensitivity to light (striking film or striking sensor) by virtue of that splitting of light.
- there is considerable believe within the industry that Sony is concentrating its efforts on the E-mount world, and new lens designs for A-mount cameras have not been introduced -- by Sony nor even by some third party aftermarket lens brands -- as a result.





