If this lens does indeed pass 390 nm UV without a large degree of attenuation, then one would be advised to pick them up as an investment. I spoke with Michael Smith the other evening and he has informed me that the developer of the light source for enlarging on Azo has largely finished the development phase. This is a totally new lamp which a manufacturer has developed entirely for this application. So the lens that you have described and it's ability to pass 390 nm UV makes it attractive. What focal lengths was this offered in? I would be looking for a 150 mm if my el nikkor does not provide the necessary band path.