Is there any disadvantage to purchasing Sony's wide-angle lens for the Z1U/FX1 and using a step-up ring rather than waiting for the wide-angle lens that will be for the V1U?

This is more of a general question actually, if I were to consider other lenses would I still have to make sure that it is a 62mm mount or do step-up rings perform the job just fine? Is there a downside?

Many folks do this and seem happy with the results, but depending on the ring and distance between the camera lens and the attached lens you can lose some zoom-through, focusing issues, vignetting, etc.

Since you mentioned the Z1 & V1, I own several of both and just simply purchased the proper lenses for each so as to ensure I won't have any problems. It's a significant added cost, but it illeviates any issues.

Fyi, I lucked out getting a V1U WA lens - there's no known, new stock of these for a few more weeks.

Also, I use Raynox fisheyes for both and got the 62mm "HD" version for the V1U - gorgeous banding - it's great!

A lot will come down to what you plan on delivering to the client in terms of quality...at least in my opinion.

Good to know, thanks! I guess I meant to say a step-down ring, not a step-up ring.

Although it's good to know that there aren't any major drawbacks either way.