The smc DA 55-300mm F4-5.8 is not the last word on telephoto, far from it. However, since I got my then-new copy back in December 2011, for less than 300 euros, it has given me a steady harvest of keepers whenever I put it on my K-7 or, later, K-3. Is it as razor-sharp at 250 or 300mm as the DA* offerings are? No, it isn't. But those possible upgrades command prices which I haven't yet been able to justify against the family budget.
What you do get with (a good copy of) Pentax's line of 55-300mm lenses, is amazing bang for the buck, and a quite capable performer for a consumer telephoto zoom, one that is usable even at 300mm, particularly when slightly stopped down. The compact form factor and the light weight will also mean that you won't hesitate to actually bring it along to an outing, and I've found my smc copy to be a great hand-held shooting option, if the light allows for it. Simply put, when I take my DA55-300 to a zoo outing with halfway-decent light, I know I will return with something worthwhile.
The images you will see when you follow the link below were all done on just two different occasions at Burgers' Zoo, Arnhem, The Netherlands - with that same lens, the bulk of them at 300mm, with apertures F6.3 or F7.1 (cf. EXIFs available by clicking the info button). I did spent some time on careful RAW post processing, but you might still get some idea of what the lens, used with reasonably-solid technique, is capable of. (The lion and gorilla images were shot through smeary glass panes, as you will often encounter at zoos, I should add.)
Burgers' Zoo - Marc
Last edited by Madaboutpix; 07-28-2017 at 01:09 PM.