Hi all,

One of my favorite all-around lenses for shooting events is a first-generation Nikon 35mm f1.4. Unfortunately because one or more of its elements contains radioactive Thorium it had turned a noticeable shade of yellow. I'd read that exposing yellow lenses to UV light, natural or not, can clear them up, so I rigged up a $17 52-LED UV flashlight to run off a power adapter and set it over the Nikon which itself was on a small mirror. In the before-and-after images the Nikon is on the left next to a clear Pentax 50mm f1.2. Though not completely clear yet I think it may be working.

If you live in a more temperate climate you can use the sun to bleach the lens, but at this time of the year its not even an option for me - where I live (Wisconsin) we get practically no UV in the winter:

http://www.cpc.ncep.noaa.gov/products/stratosphere/uv_index/gif_files/mke_09.png

In the picture of the UV flashlight is the next lens that I hope will de-yellow, an Olympus 55 1.2.

Just thought this may encourage others with yellow glass to give it a try.