72mm attachment thread - so it should screw straight onto your AX2k. Be very careful though as the Sony's front element is right up against the filter threads, so if the Tokina's rear element is protruding in any way the two elements might touch as you screw them together - with disastrous results!

The Tokina is a 0.5x zoom-through optic so I'm betting you'll get wild barrel distortion. The more you zoom towards telephoto the less obvious this will be, but as soon as you zoom just a little bit it'll be time to take this lens off. Use it just for the times when you MUST see wider, regardless of the consequences. Because of the distortion and extra flare this won't be a fit-it-and-forget-it lens, no way.

I'd sure like to try it on my NX5 and compare it to my Aspheron (0,52x).

tom.

I 2nd that tom! Adriano great find!! I'm so tempted just to buy it and try it at that price 100$ is almost a no brainer. I would need this for certain wide angle situations as tom said regardless of distortion or not. It does look to have substantial distortion however given the picture examples on that link. Tom do these converters soak up any light?

These converters are generally three element designs. Sometimes the real cheap ones are two element, but the Tokina name should ensure it's a three element (the spec gives no clue).

If they're fully multicoated they absorb so little light it's un-noticeable - maybe 1/8th of a stop tops. You need make no adjustments whatsoever. Some people have told me they 'make the camera more light sensitive'. Duh, they fit the wide-angle and it 'sees' a lot more sky, changing the green field view at f/4 into a sky-filled shot asking for f/8.

tom.