My previous blog (Sony NEX-5N First Impression) has given an introduction on this lens converter - Sony VCL-ECU1. Here is a more detailed post on this lens converter show what this converter is capable of.
First, this converter is suitable only for E-mount 16mm F2.8. There are reviews on other websites saying that it is also compatible with Panasonic M4/3 lens 14mm F2.5. I can't test this out since I don't have the lens around. The converter has a multiply factor 0.75x, that is, focal length of 16mm will be converted to 12mm after mounting.
Some may not know how much wider 12mm is compared to 16mm, and 18mm end of the kit lens 18-55mm. I have taken two examples so you may see the difference.