I know that to get the same FOV on full frame and crop-body, e.g.
85mm for cropper and 135mm for full frame, at the same aperture, full frame will have less DOF due to the longer focal length.
i have a 7D and most of the portraits I've done are waist-up. I saw this picture and it looks great to me.
My question is that : can you achieve similar result with a 85mm f1.8 lens or 200mm f2.8 lens on a cropper? I'm inclined to say yes since in this photo, background is far away from the subject. But I'm not sure what if the background is close to the subject, can you get great full body portrait that seperates the background away on a cropper? can it be achieved on a 85mm f1.8 lens? or 85mm f1.4 lens is needed? how about 200mm f2.8?
sorry for so many questions. I'll do some test myself later when I have time. In the meantime, it'll be great to hear from you guys.