Excerpt: Really nice and clear photographs, it does focus somewhat slow but not too bad. The range is great, personally would prefer something like a 200 but that is just me. Where I was most happy with this lens was at weddings, I was really happy with it's performance especially outdoor weddings, since indoor autofocus in low light is not good at all, but that is probably the camera.
Excerpt: I am extremely pleased with the Pentax SMCP-DA* 50-135mm f/2.8 ED. It is a great lens. I love the Bokeh. Image quality is superb. I like the fact it is water sealed, I use it with a K20D and K5 both of which are water sealed. I do a lot of photography on whitewater rivers while rafting and this is a necessary feature also living in Western Oregon I spend a lot of time in the rain. The aspect of the lens I am most happy with is the auto focus.
Pros: Durable, Easily Interchangeable, Fast / accurate auto-focus, Nice Bokeh, Rugged, Strong Construction
Summary: I like the size and price of this lens, compared to similar optics from other manufacturers. The build quality is good, although I'd like it to be a bit beefier. The autofocus is fast, although not as fast as some other lenses in the medium telephoto-long telephoto zoom style. I decided to buy it because I knew it would work flawlessly with the camera technology I already had, and that it was a proven performer from a reputable company.
Summary: First the good: This is an impressive lens in both feel and looks. There's no mistaking that this is professional glass. For portraits and non-flash situations like stage performances, I wanted a lens that was top-notch in sharpness and overall image quality. According to the specs and the various reviews, this lens delivers...and that's why I bought it. Now the bad: I got a bad copy.
Summary: I have been using this lens for a couple of weeks now. I purchased to shoot my daughter's cheerleading competition in Disney World. In fact I am sitting in the airport now waiting for my plane to Orlando, while writing this. I bought this lens to replace a Sigma 70-200mm zoom. So far this is a much better lens. The SDM motor is great. Much faster and quieter than the motor in the SIgma (not HSM) I spent over $900 for the Sigma lens a few years ago.
Summary: I just got this lens today and although I haven't taken it out the house yet the few shots from around the house impress me. Great build. No lens drift like the Pentax 25-250mm that I own. It's fast. The Pentax 25-250mm may have more range but the focus speeds can't catch the action stuff. This should be a great compliment to my Pentax K200D. Pentax is very underated as far as i'm concerned. This lens may be up there with some Canon's. Maybe!
Summary: Very solid construction. All zoom and focus is completely internal so the front element does not rotate or trombone. Extremely sharp and contrasty. HSM focus does not appear any faster than screw drive - focus is accurate but not especially quick.