If I have left you with the impression that I am totally enthused with the NEX at the expense of the A-Mount, let me correct that impression. I have no great and pressing desire to own a NEX3/5 as an alternative to my A-Mount kit.

I know that some people have worries about the future of the A-Mount but I don't entirely share them. Sony's Katsumoto has stated their committment more than once and it is pretty well confirmed by their significant investment in the "G" lenses (long term returns), 35mm 1.4, 70-200, 70-300, 70-400, 300mm and the upcoming 500mm f4, not to mention the Zeiss range.

If I have a concern it's over the future of the screw drive which, looking at the number of SSM and SAM lenses from Sony, does not figure in Sony's long term plan. I initially thought this was because of the necessity of contrast detect AF (for Video) but, from what we've seen so far of NEX, SSM doesn't appear to perform much better than you would expect from a screw drive with CDAF. It seems that SSM and SAM will work with CDAF but not as well as do the two E-Mount lenses; SSM and SAM operation at the moment is a bit "buggy" and so has been temporarily disabled while Sony work on it so, although probably useable, these A-Mount lenses are less than optimal. Clearly the E-Mount is a complete departure from A-Mount with very little backward compatibilty and, being an all-electronic mount, plays to Sony's strengths and therefore their preferred direction of development.

With the NEX3/5 Sony has chosen to deliver a small camera to show what's possible but it's just as possible to deliver EVIL in a DSLR sized, better handling package complete with control wheels, buttons and in camera stabilisation. The first of these, NEX7(??) will likely appear later this year at Photokina (speculation) and may therefore give us a first sight of the true competitor to the A-Mount. Where EVIL can't yet deliver acceptable performance to (D)SLR users like us is in the area of AF and in the viewfinder.

At this point in time, no EVF (electronic view finder) comes close to a good Pentamirror system let alone a Pentaprism, however the issue is far from insoluble and Sony are probably best placed to resolve it.

CDAF (contrast detect AF) so necessary for Video and Main Sensor Live View is very slow (especially in low light) compared to the PDAF (phase detect AF) we currently enjoy. Unlike PDAF, which measures and then brings the lens into focus in one movement, CDAF must creep up to the focus point in small increments involving hundreds or thousands of measurements. Inevitably this is a comparatively slow process although it does have the advantage of accuracy and the phenomenon of front/back focus becomes a non-issue. How long it will take to bring CDAF up to challenge the speed of PDAF I have no idea, but all manufacturers are investing considerable sums into R&D. Sony even has a patent describing the incorporation of PDAF style sensors into the tiny photosites on the sensor, maybe we end up with a hybrid system!

So where does this leave the A-Mount? The writing is clearly on the wall, still in fairly small font but probably in this decade. The A-Mount will be pushed more and more into a niche position, maybe even limited to FF, who knows? In the meantime the A7xx will make its appearance and, from what we've seen in NEX and the A4/5xx, we can be sure that Sony has not been standing still and that the A7xx will be a big enough step forward to satisfy existing users. Whether it will surpass the opposition in any area apart from video remain to be seen but, so long as it's a good step and at a reasonable price point, it will be welcome. I also think we will see something of A9xx for an appearance next year.