They have the same mount. That way lenses are interchangeable regardless of which sensor you have. They just use less glass to make the smaller DX image circle to cover the smaller DX sensor.
Discussion
*not to scale, not even close
Big image circle, big sensor. And vice versa. You can use the big circle with the small sensor, though. If you use the small circle with the big sensor, the corners and edges will be dark because there's no light there.
sweeeeet thank you!!
Yeah I didn't know that.