Easy Question: How do I turn camera off in a conversation?

I occasionally need to turn on my mac camera to show something during a Lync call. It works great, but I can't figure out how to turn the camera back off after I am done showing the other attendees whatever I used the camera for.

I am on 14.3.3 on El Capitan 10.11.4.

I press the camera image in the Group Conversation window to start sharing video but it doesn't respond to any form of right-click, alt-click etc..