First I'll say I swear by Tamron SP or Vivitar S1 lenses and now have 4 Tamron & one Vivitar.

But new Tamron or Sigma lenses are now primarily aimed at the digital SLR market of which few cameras at present are full (35mm) frame. So that may well be the problem.

Personally I have stopped using 35mm completely, and apart from use as a diary I'd dropped 35mm as a serious medium 20+ years ago except for Rock concerts. But the specialist push processable E-6 films were the first to go . . .

I have 2 superb Tamron SP lenses, a 17 - 35mm f2.8 and a 28 -75mm f2.8, but they'll never get used with film.