Lovely set of pictures.
Some of the images have background blurs the shape of a 10-sided polygon, which suggests the lens has 10 aperture blades and is stopped down a little?
I should have mentioned that, no it is fully open, but factory preset to have the aperture close in a bit, most likely to achieve certain pre defined parameters. The lens is much faster than f4.5, based on the front lens and its entrance pupil size.
The Russians' competence is very often underestimated. This also applies to optics.
Your images are wonderful.
Thank you, yes, I really like their optics, especially these lenses, made under Prof. Volossov at GOI and calculated by three women working for him: E. Grigorieva, I. Driatskaya and S. Frolova, all calculations done per hand (I have his very rare book on optics). And it is my pleasure to prove even today, what amazing work they have done back then!!
