[Ubuntu_user]

Oh yes, I would drop the extra 100mm right now to have the Tamron 70-200mm instead of 55-300mm. It's larger and heavier though.
And yes, I would definitely recommend buying used from here on the forum.

[mikeSF]

dont do that!!!! now im drolling over this thing!!

BTW are sigma/tamron teleconverters interchangeable? meaning i can only tamron lenses on a tamron TC? just cause it seems i cant find any tamron TC for sale here in norway but there are sigma 1.4x and 2x

i have heard some of the sigma TC's will work but neither company shows compatibility in the literature.

BTW, i have the Tamron F 1.4 and it does not work right with the Tamron 70-200/2.8. Others have gotten it to work but mine will not MF without dragging the motor on the camera. fyi. Tamron cust service says they are not compatible and to discontinue using.

[bobell69]

If you do choose to go the Sigma route then I suggest that you get the APO version rather than the DG version. The APO is a much better lens. I have the APO, but have recently shelved the lens since I got my Sigma 70-200 F2.8. If I need to stretch out further I either put a teleconverter on it or use my FA*300. Either way I get sharp images.

I have taken some nice images with the Sigma 70-300 APO over the past couple of years. This one is a cropped image taken last winter. I don't normally take the lens to 300 except in a pinch. Usually I pull it back to about 280 for a sharper image. The difference in zoom is insignificant, but the difference in the sharpness of the image at 280mm vs 300mm is noticeable.

[excanonfd]

dont do that!!!! now im drolling over this thing!!

BTW are sigma/tamron teleconverters interchangeable? meaning i can only tamron lenses on a tamron TC? just cause it seems i cant find any tamron TC for sale here in norway but there are sigma 1.4x and 2x

As long as the TC is K mount, it's completely interchangeable but if you try any TC on those consumer zooms you were thinking about, you can forget about AF.

[reeftool]

I have had excellent results from my Sigma 70-300 through the years. Stopped down to f8-f11, it is very,very good. The macro mode is perfect for close ups from my kayak. If you mostly use it in that kind of light, then you may not notice any difference between the 2 lenses. I dropped my Sigma a year or so back and it and the zoom doesn't work right although the AF works fine and optics don't seem to be effected at this point. If I replace it, I'll buy the 55-300 but before the accident, I don't think it would have been worth it for my uses. The Pentax has a little more range and a little better wide open. I have some long MF glass which gets used a lot so this isn't a high priority for me at this time.