This is a detail from a photo that I took with a Fujifilm XF55-200mm lens. The lens was zoomed all the way to 200mm, and the aperture was wide open—f4.8.
I wonder whether somebody knows the cause of the dark rings in the otherwise mostly-uniform, circular* bokeh.
My question partially duplicates another question, but that question was a two-parter, and nobody answered the part about the dark rings with the bright centers.
Additional info: I was using a lens hood—the one that came with the lens, though I would expect that any defects caused by the hood would show up at the shortest zoom setting, not the longest.
There were no filters or other accessories.
* I'm assuming that the ones that aren't perfectly circular are images of "points" of light that were not perfectly point-like.