It works fine with my Tamron 300 2.8, DA*200 and DA* 60-250, as well as the DFA 100 macro, the Tamron 90 macro, the Sigma 70 macro. I tried it but don't recommend it on the DA 55-300 PLM. Those are the lenses I've tried it on. It needs to be a DA* quality lens, consumer grade zooms are generally not sharp enough, but I'd be amazed if it didn't make your Tamron 70-200 280 sharp mm. The increased resolution according to Pentax engineers is -3% from the 40 % nominal. As long as your lens has extra resolution, and as far as I know the Tamron 70-200 is excellent, it should give you a 37% increase in subject resolution under perfect circumstances. The only thing that might disapoint you is that 280mm just isn't that long. You get a lot more from it on a 300mm lens.
From todays shooting.
Enough of the trying to get a K-1 to do what a K-3 does... back to what works. My life just got so much easier.
K-3
Tamron 300 2.8 with HD DA 1.4 TC. (420 mm ƒ4 [630mm FF equivalent])
ISO 200 ƒ8, AV mode
Dark eyed Junco
Hairy Woodpecker
Female purple finche.
Male Purple finch
Blue Jay
White Throated Sparrow
Red Breasted Nuthatch
But do wait until a user who has it comes on to tell you if they play nice together.
Last edited by normhead; 05-06-2019 at 06:06 PM.