If you have a third party crop lens that does not intrude into the camera body, you can use them on a FF body.
NOTE: if you use a lens that protrudes into the body, you run the risk of your mirror hitting the back of the lens and damaging your camera. DO NOT USE SUCH LENSES!
The three shots here are:
1) with a sigma 30F1.4 crop lens.... note the severe amount of vignetting. You could crop this image to a slightly wider field of view as on a crop camera.
2) With a Tokina 11-16 F2.8 lens at 11mm. Also a severe amount of vignetting, you could crop this image to a slightly wider field of view than a crop camera.
3) With a Tokina 11-16 F2.lens at 16mm. A bit of vignetting at the corners, but the whole image is usable....
NOTE: if you use a lens that protrudes into the body, you run the risk of your mirror hitting the back of the lens and damaging your camera. DO NOT USE SUCH LENSES!
The three shots here are:
1) with a sigma 30F1.4 crop lens.... note the severe amount of vignetting. You could crop this image to a slightly wider field of view as on a crop camera.
2) With a Tokina 11-16 F2.8 lens at 11mm. Also a severe amount of vignetting, you could crop this image to a slightly wider field of view than a crop camera.
3) With a Tokina 11-16 F2.lens at 16mm. A bit of vignetting at the corners, but the whole image is usable....