The shorter the focal length, the more distorted it will be when you stand too close to the subjects regardless of sensor size. For wide shots especially landscape, FF (or medium format if you can afford) will be ideal as you can use longer focal to cover wider shot, thus have less distortion compared to using apsc/m43 with shorter focal for similar field of view.

On TS question on what is the "right focal" for group shot without having to stand back too far.......really depends on how big the group size and max distance you willing to stand back. There's is no wrong focal length, there's only the right focal length for what kind of shots you want. So do specify how big is the group, and how close you want to shoot (preferably with a draft photo or something) so the generous lowyat nerds here can give you the correct advice. Depending on situation, it is probably advisable to choose different location so you can step further back than to get a fish eye lens just to fit everyone.

This post has been edited by DaddyO: Mar 18 2017, 04:33 PM