at risk of going a little OT which nex do you have? do you have an EF lens adaptor for it? if so how well does the EF adaptor work and is it a sony or 3rd party beast?
I have a NEX 5n. Great sensor! Same 16 MP sensor as the Nikon D7000 and the Pentax K-5. Great video as well. I'm very happy with the camera. The two problems are the lack of a hot-shoe (can't use PocketWizards) and no 85mm prime. If I get an EF-M I'll use it for stills (with my EF 85mm f/1. and use the 5n for video (I prefer Sony video).
I do not have the Metabones http://www.metabones.com/sony/buy-eos-nex-adapter?virtuemart_product_id=4&virtuemart_category_id=13 EF to E-mount smart adapter. Sony does not make an adapter.
If I were going to use non-Sony lenses, for video, I'd use the small/light high IQ Nikon AIS manual focus lenses. Their aperture ring can easily be de-clicked. See Duclos CineMod http://www.ducloslenses.com/pages/cine-mod
Hope this helps.