Quote Originally Posted by Michel Hardy-Vallée View Post
It's an obvious matter that some lenses render colours in a less saturated manner than others: old uncoated lenses, for example, not always give as rich colours as modern multicoated ones.

But is it because such lenses increase colour saturation (e.g. by selectively letting certain wavelength corresponding to primary colours go through more easily) or because they avoid the problems, such as flare, that desaturate colours?

I'm suspecting coating and glass type have a lot to do here with the avoidance of problems, in that they reduce parasitic light due to internal reflections, but I wonder if there are other variables at play.
With color reversal films, slight overexposure reduces color saturation, slight underexposure increases it. Great stress, slight.

In my experience with lenses in shutter, shutters that run slow are more of a problem for color saturation, at least for reversal films, than lenses' coating or lack thereof. I have, though, used a couple of single-coated lenses that were flary and needed careful use of hoods to reduce the effect of light sources outside the frame on color saturation. Prime examples are 150/9 and 210/9 Konica Hexanon GRIIs. Both single-coated, both problematic with difficult lighting. I keep the 210 GRII in the closet, use a 210/7.7 Beryl-S instead; it isn't quite as sharp near wide open but gives much better color saturation. Oh, yeah, Beryl-S = Dagor and it is single-coated.

Mustafa, once upon a time lens design was done with hand calculations. Now fast digital computers are used. They're much much faster than people, and because of this are better at optimization. You're too young to have done large calculations manually, but when I was a young graduate student I burned out several electromechanical calculators. They died in clouds of blue smoke.