Since the render was so noisy, I used intel open image denoise and blended with the original image. 25% original, 75% denoised one. Also accumulated more samples, this is at 614 spp

a diagram of the lens tracing. rays go into housing, go through 2 elements, then aperture, then back element, than to sensor. Internal reflections are rare and require an even number of bounces to continue the path. Only 2 bounces are considered because 4 is very low probability. Every iteration, I send one fully transmitted ray and a ray that bounces off 2 random surfaces(out of the 6). Then I weight the contribution to the probability of all events

514 rays per sample. ~10 hours render time. 1600x1200 pixels. f2.8 aperature and 24mm sensor size. Each ray does a "MIS" of the internal lens reflection. Added volumetric path tracing with phase function. I gave the overall scene a slight volumetric density to get the god rays.

I rendered this with lens tracing through a Cooke Triplet lens system using f2.8 aperture. The lens info was computed from Optiland. All the ghosting is from internal lens reflections. The rings are from oversizing the sensor. - Not my final submission