I would recommend a fast f/1.4 50 or 55mm lens to provide more options in controlling DOF. Also worth noting, however, is that the extremely fine FA 77mm f/1.8 Limited when used on FF is a different ballgame than APS-C for portrait. Bookeh is excellent, size and weight are small, so if interested in doing candids, it does not draw attention to itself. For that, APS-C may be better with it. A 50mm lens becomes a little short for portrait with FF.
I was still shooting film when bought my FA77mm LTD, and the very first shot I took with it was while walking with a young friend through a wooded area near a Lake Michigan shoreline. The lighting was near ideal that day and as we were in an especially good spot, I suggested a photo, to which he agreed, I walked a bit ahead, turned and his expression was prefect, my VF revealed a good aperture/ shutter speed in the "P" mode so I instantly fired one shot. As it turned out, he said it was the best photo ever taken of him, even better than professional studio work! It did come out beautifully.
Last edited by mikesbike; 08-02-2018 at 08:08 PM.