These are the actual imaging chip(s). The common sizes found are “Super 35″ (http://en.wikipedia.org/wiki/Super_35), 2/3″ (not really 2/3″ at all — see http://www.dpreview.com/news/0210/02100402sensorsizes.asp).
Super 35 sized sensors are found on the digital motion picture cameras, such as the Sony F35, Red, etc. 2/3″ sensors are typically found on traditional video cameras used for news shooting like the Sony F900, F950, and nearly any other professional camera that was not designed explicitly for motion picture production. These cameras are called “broadcast” or “ENG” (Electronic News Gathering) cameras, as opposed to Cine- or “EFP” (Electronic Film Production) targeted cameras.
The reason for the detail here is that the precise sensor width is the measurement that you need in order to accurately calibrate a lens. For the high end professional cameras, this is published, and usually found in the manual. It always deviates slightly from the “standard” Super35 size of 24.9 mm, so if you know you’ll be dealing with a certain type of camera, you want to hunt down that sensor size early on. We have a few of the more common standards built into Previzion, but it’s worth planning ahead.