My 7-blade 35mm gives 14-point stars at f/16 — what’s the simple reason odd counts double the rays while even counts don’t? If makers pushed blade counts into the teens or went perfectly curved, where does this go next: more rays, softer ones, or does diffraction just cap it?
It’s just edge diffraction: each blade edge throws a pair of spikes; with an even count, opposite edges are parallel so their spikes overlap, but with odd they can’t, so your 7 at f/16 becomes 14. Push blade counts into the teens or use rounded blades and the aperture gets closer to a circle, so the spikes get weaker/softer and diffraction just gives you more glow than more rays — . Nice explainer here: https://photo.stackexchange.com/questions/28612/why-do-odd-number-of-aperture-blades-produce-double-the-number-of-starburst-rays; have you tried a 9‑blade rounded iris to see the difference?