My son has been using the Rokkor 135 f:2.8 (mid 70's vintage) on extension tubes. He has gotten excellent results near 1:1 and lower reproduction ratios. We looked at slides taken with that combo side-by-side with Olympus 90mm macro shots (about 1980 vintage lens) and 100mm f:4 Macro-Elmar shots, and his work looked just fine by comparison. The person shooting the Oly macro wasn't expecting much, he's a professional photographer who's done extensive macro work over the last 20+ years, and was impressed by the Rokkor's performance.

Lee