Do anybody know aprox. how many 20x24 cameras are out there being used ?
The number is surely fairly small. Cameras this size are either home made or built on a custom basis. So far as I know they have been made in recent years by Lotus, Wisner, Chamonix, Ebony, and now Richhard Ritter and Keith Canham. I would guess that there are less than a hundred full function (excluding one shot pinhole cameras, etc.) 20X24 cameras in the world, probably a lot less than a hundred.
Second, I suspect that most if not all of them have been used or will be used. People tend to purchase this size camera for specific projects and/or for special subjects, not as a general purpose camera. The price of 20X24 pan film, when you can find it, is over $20 a sheet so the use of the camera has to be well planned.
I know of one 20X24 Wisner cameras that was purchased with several film holders, a 20X24 contact printing frame, and several boxes of 20X20 AZO, but was never used by the original owner because the project he planned for the camera lost its rationale. But the second owner has used it quite a bit, or so I understand.
Sandy King