FF Bodies Using EF-s Lenses in Crop Sensor Mode?

[hmatthes]

Just a curious stills shooter jonesing for a 5D-IV body...
Not an engineer... seems to me that the image circle of the EF-s family are designed for APS-c sensors & some FF bodies can select "Cropped" mode, therefore selecting in middle of the sensor.
Since the physical mount is the same, meaning that the distance to the sensor is the same, and not seeing rear elements deeper than the mount (no mirror crash?) -- why not use a EF-s on a FF?

 

[tcmatthews]

Canon EF-s where designed to not physically fit on camera. Other third party lens manufactures lenses may fit.

 

[Loswr]

The physical mount is not quite the same. EF-S lenses have a plastic baffle that prevents them from mounting on FF bodies. If you remove that baffle (it's simple), you find that the rear of some EF-S lenses does interfere with the mirror on FF bodies.

 

[hmatthes]

Thank you forks... I just knew it had to be something like this.
My 70D has helped my create gorgeous large canvas prints that get good reviews. Maybe I don't need a FF sensor after all.
My old L glass from the film days works on the 70D as do the collection of STM glass. I'm a happy boy.