Is flange focal distance of a camera system measured from the front edge of the lens mount to the film plane, or the back edge of the lens mount to the film
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terminology - What exactly is focal length when there is also flange focal distance? - Photography Stack Exchange
![terminology - What exactly is focal length when there is also flange focal distance? - Photography Stack Exchange terminology - What exactly is focal length when there is also flange focal distance? - Photography Stack Exchange](https://i.stack.imgur.com/hfuQz.png)