Originally posted by rayallen There is absolutely no reason why a 55mm f1.8 would go yellow. They did not have any rare earth glass elements. I have multiple examples of that focal length and all of them are "water clear".
so far as several of us here have admitted, 55s do indeed yellow.
I also have a number of examples, here is my list of 55's:
Auto-Takumar 2/55 - clear
Auto-Takumar (early Super variant) 1.8/55 - very slight yellowing
Super-Takumar 1.8/55 - some yellowing
Super-Multi-Coated Takumar 1.8/55 - yellowing (more than others)
SMC Takumar 1.8/55 - yellowing (not as much as the S-M-C but close)
none of these are anywhere near as yellow as my S-M-C 1.4/50 but it is indeed there. I even noticed a yellow cast when using my 55's when looking through the viewfinder of my istD (something I did not see with my K110D or K-m. its also visible when using the 1.4/50)
another member used a geiger counter and confirmed radioactivity with a 55. Asahi Optical may have only ever publicly announced use of thorium in the 1,4/50 but that doesn't mean that was the only lens they used it in.