Originally posted by audiodoc 
HI Giklab, thanks for the info esp about the TC's. For the wide end I was just going to bring a panasonic bridge camera. On my last trip, I seldom ever used the wide angle range. My first instinct was to go with the 50-500 but then I read greater reviews on the 150-500.
I'm posting a bit late but hopefully not too late to help. In my opinion it's a close call between the latest Sigma 50-500 OS HSM and Pentax 60-250.
I have the latest version of the Sigma 50-500 and am satisfied with the sharpness on my K-5. I really like the OS because it has a panning mode; the lens stabilizes in the up-down direction while you can pan left-right to follow birds. Note that older versions of the 50-500 might be softer at 500mm than the latest version so be careful if buying used.
The Pentax 60-250 is undoubtedly sharper at 250mm. Once you crop to a 500mm equivalent I don't know whether Pentax or Sigma gives a better image (but they'll both be good). If carrying weight is a concern on your trip the 60-250 weighs half as much as the Sigma.
The Sigma 150-500 has no advantage, other than cost, over those 2 lenses. It's weight is nearly the same as the 50-500. You lose the ability to zoom out beyond 150mm; going wider lets you take some landscape and people shots without changing lenses.
The Pentax 55-300 is a good, inexpensive, lightweight lens. It's one of the best bargains in Pentax-land, but the 60-250 and 50-500 will give better images. In my opinion the 55-300 is a perfect lens to keep in your bag in case you unexpectedly need a lot of zoom, but for a safari where you know you'll need telephoto stick with the 60-250 or 50-500.
Alternatively, there's the Pentax 300 prime. Maybe the best image quality but limits you to a single focal length; might be a showstopper if you are only bringing one lens.
Post #12 by savoche
Similar Threads 
