Well, right now I have a bit of a collection.. cannon FD, Nikon AI, Nikon AF, Pentax k, Minolta MD, and soon to be M42.
To put it in perspective, I cannot afford Leica/Zeiss/canonL glass.. so I guess "reasonably priced" or even inexpensive.
But my main reason for asking is to understand what goes into making a good zoom lens.
For primes, the number of glass-to-air surfaces affect contast, as does multicoating all surfaces. Prime lens designs, such as tessar, planar, plasmat, etc are easy to recognize. However zoom lenses can have 12 or more lens elements so it's anyones guess as to what designs are better. Also primes can have rather simple barrels since the whole lens unit will move. But with zooms different portions of the lens move independently, and thus I bet that precise mechanical design and manufacture plays a much larger role than in a prime lens.