Canon FL 55 mm f/ 1.2 Lens

Spherical abberation (glow) is relatively tame wide open, I've seen worse from some f/1.8 lenses.  Sharpness is great for this lens, though contrast is low which affects total resolution.  Looks beautiful, built wonderfully, and handles great.  Not as heavy as other 1.2 lenses (but still heavy on a small camera).  The quality of the glass is excellent, very little relative variation in sharpness across the frame.  It's currently one of the lowest priced vintage 1.2's on the market.

Weaknesses:

Low contrast which can hinder resolution up till f/2, bokeh can get busy on difficult backgrounds.  A little difficult to focus wide open.  Can flare easily.

Comments:

I'm currently using this on a Fuji X APS-C camera.  This lens has two variants, identified by the text on the front ring.  The picture in the description above has the later version.  I'm not sure what changed, if anything did, between the two optically.  It's built like a tank and because it handles so well I love using it.

I picked my copy up for $165, but it can sell for up to $200 and maybe even a little higher.  It was a little dirty but after some cleaning it's in mint condition!

There are no radiactive elements in the lens, I checked myself with a geiger counter device.