I have used a few 300mm and 400mm on prime, zoom, and with addition of 1.4x and 1.7x TC, my most satisfied lens is Pentax F* 300mm f/4.5. The lens best itself for its small size and relatively lightweight compared to others. It will take the Pentax DA* 300mm f/4.0 to beat this lens in the 300mm. I highly recommend this lens for wildlife, use good TC to reach 400/500mm. It has excellent color and sharpness. My copy is pretty beaten up but it is my most used 300mm for wildlife ever since I get it. #1 #2 #3 #4 Pentax F* 300mm f/4.5 The above was a posting that I did in PF way back in 2009 and I likely took this pictures with K20D. Time flies and I don't think I have the patience with terns especially I remember them moving fast and not to easy pattern for anticipation.