The Thambar was made, in small numbers, specially to meet the demand of some portrait photographers. I recall being told by an old chap who had used it that he took quite some while to get the hang of the clear glass bit with the opaque spot at its centre. Several makers of SLRs have made soft focus lenses, most designed to eliminate the sharp resolution at the axis by under-correcting spherical aberration, but I have never heard of one made for an RF camera. Some lenses -- the Summitar comes immediately to mind -- give low contrast at maximum aperture, which achieves a somewhat similar effect. That is true of the 90 mm Elmar as well.