This is a bit of a tricky one but maybe someone can help with this.

I have a client who wants to commission some art for behind his office desk that will take up the whole of his studio monitor's webcam field of view, but not the whole width of the back wall. 

Unfortunately we can't just use his monitor and set up some basic triangulation and tape measures on the wall as he's out of the country for the next few months.

The problem that I have right now is that the artist is looking to start asap and I have been tasked with getting the dimensions to them so there are no delays... 

We don't have a studio monitor on hand, the client is away from home so is unable to check with his, and online it only advertises the Studio monitor as having a 120degree field of view that centerstage has available. 

What viewable angles does the webcam have when not using centerstage? It can't be the full 120 degrees can it? Can he force a zoomed in/cropped ratio?

Any help would be appreciated.