I can also recommend the Pentax DA or DA-L 55-300. It's a terrific lens.
Originally posted by victordeamorin A 18-250 lens is thus a ~12x zoom going from wide-angle to long tele. The difference between 250mm and 300mm is not big, about 15%.
The difference between 250mm on the 18-250 and 300mm on the 55-300 can actually be a big difference, since the 18-250 is an internal focus lens & the 55-300 isn't. At infinity there isn't much difference, but the closer you get to your subject the greater the difference becomes.
I once checked the difference between an internal focus and conventional design lens at the same focal length and found that from a distance of about 15 feet, a 300mm internal focus lens was the equivalent of about 190mm on a non-internal focus lens. A whopper of a difference.
For this reason, I prefer non-internal focus lenses when it comes to tele ranges. And the 55-300 is one of the very few non-internal focus AF lenses out there.