What you say about the risk of fogging is true, although I have not had any lens develop fogging after a CLA. However, what 50s Leitz lenses have going for them is great resolution and field coverage together with significantly lower contrast, which I personally like in color transparencies. I reserve my latest-model Summicron for b+w, where I find I need to downrate film even further than the usual 1/2-stop and cut development more than I do with other equipment (such as 80s Nikkors and view camera lenses ranging from 1950s to new). I find that the combination of a new Summicron and high-saturation color film gives screamingly high contrast.
Originally Posted by Nicholas Lindan