I have both the 50mm f/1.8, and the 55-300mm f/4-5.8 lens.
I would definitely recommend the 50mm 1.8 (or a similar “fast” lens) if you’re interested in the “blurry background” look. There’s something about fast lenses that changes the “look” of your photos.
You might also consider the Pentax DA 35mm f/2.4 lens, which offers you approximately the same focal length on a K-3’s APS-C sensor, as a 50mm 1.8 would offer on a full frame sensor. Right now you can buy the Pentax 35mm f/2.4 (Open Box) for only $90.00 from B&H Photo & Video, which is Adorama’s main competitor. They are both well reputed sellers, and I would not hesitate in the least to order from either of them.
As for the 55-300mm lens? Well, like I said, I own it… I don’t know exactly what to tell you about it. 🙂 I got it for a whoppin’ good deal, so I suppose I shouldn’t complain. I only paid $120 for it, but I was honestly expecting a lot more from it. I have seen reviews which praised it highly, so I was expecting it to be pretty good! In reality though, my copy of the lens is very soft wide open, and while it does sharpen up when stopping down, it’s never really very sharp. It also seems to be a very “noisy” lens, I’m used to my Pentax DSLRs having very good low-noise performance, but this lens seems to bring out the noise like crazy! I wonder if I just happen to have a bad copy, seeing as all the reviews seem to think it’s quite good, so don’t just take my word for it. If you’re interested, here’s a Flickr album with a few images taken by the Pentax HD 55-300mm WR. One good thing about it is that it is weather sealed, which is always a plus!
