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Owner reviews: Spiratone 135 mm f/ 1.8
Really an excellent fast 135mm overall, with very solid build, excellent IQ (sharp wide open, with modest contrast), and exceptionally smooth transition to out of focus. YS mount allows adapting to just about any camera.
Big, heavy, akwardly large diameter for its short length, lens with smooth, but tight, focus feel... which means it sometimes tries to unscrew from the mount rather than focus. It doesn't seem to cause flare problems, but some of the inside of the lens barrel is actually shiny metal. Things very out of focus can look a bit nervous.
Pricing is wildly variable for this lens. I've seen them go for over $800, but I paid $150 for my pristine copy.
The moderate contrast and smooth transition to out of focus means peaking doesn't work as well as magnified live view on LCD or EVF for focus.