Originally posted by dfujevec I think it has 19 blades. The lens is very sharp wide open and very easy to focus. Here is another wide open proof
I am not sure, there are so many it's hard to count
I picked up this lens to be the top end of my M42 kit. and also find it very sharp and easy to focus. I use it on my K10D which I put a split image into. Since getting it, I have been looking for more and more presets with round apertures at all stops because the bokeh is quite different than modern lenses. In fact, if you search the forum, there is a thread I started
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/87425-definite...h-society.html with the intent to discuss the qualities of lenses with high numbers of aperture blades and round at all F Stops apertures.
here are a few shots of mine with the 200F3.5
I have yet to test it side by side with my Vivitar Series 1 70-210 F3.5 (version 1) but it would be a great comparison.