| There's also the new Sigma 50-150, which might challenge the 50-135.
There are advantages to the Pentax, though IQ differences between the 50-135 and the Tamron 70-200 are hard to appreciate - both are stellar lenses. The Sigma 70-200 has been commented to have less contrasty images but otherwise comparable.
Hard to advise - I thought you answered your own question by wanting some length and cost-effectivenes (70-200's the winner), though size would be a problem (it's significantly bigger and heavier than the 50-135) and it's not weather sealed. |