The Biotar family are all (AFAIK) double gauss 6/4 lenses, which have distinct bokeh which tends to swirl near the edges. This particular lens is interesting because it is designed for the 16mm Pentaflex film camera, and which has a smaller than usual image circle which doesn’t quite cover FF. The advantage of this for me and my strange tastes in bokeh is that it thus allows the very edges of the image circle to be used, which includes quite a bit of distortion and swirl at the edges. Not particularly desirable for normal shooting, but it does add something to closeup bokeh shots.
