Has anyone done a comparison of russian Industar lenses---Industar 61 and Industar 61 L/D.....Does the L/D infact contain rare earth and the radio active element Lanthanum, and if so does this improve contrast etc....

The L/D lenses I believe were issued with the Fed 4 and Fed 5 series, and are also leica screw mount etc.

Maybe some one has an example of each?

Thanks
Dave in Vegas