> So the 28-50mm is like the wider version, in that it is essentially 3 primes in one?
Yes.
> It does not cover the focal range in between?
Correct. The images taken when between the marked settings are soft. The name "Tri Elmar" is appropriate. It's not a zoom. I has 3 reasonably good settings: 28, 35, and 50. Frankly, I consider it a "35mm + and -". The 35mm is the best, the others convenient additional settings.
That said, I don't use the lens any more. The Leica apo 35 can do it all better.
Paul
www.PaulRoark.com