same as the Tamron 18-400, it is likely to give you vignette: you probably end up (at least at some focal lengths and with focus set at certain distance ranges) seeing part of the lens’s circle of projection at the corners of pictures taken with that lens attached to an FX camera.It can be used on FX cameras (even on medium format and bigger for that matter), the downside is that not the whole sensor will be hit by the light, leaving you with black corners.