Summary: I use this lens on a Pentax K-5 and although I have only taken a few dozen pics with it I tried to vary the subjects to geed an idea about how well this lens would produce. Wide open it vignetting is pronounced, stopping down reduces it dramatically especially from f5.6 onward, at f4 it's noticeable...
Summary: This compact gem is perhaps the perfect little walk-around lens for your Pentax. Unobtrusive, it gives your camera a unique perspective that doesn't scream wide angle but is wider and can be more useful than (35mm equiv.) 35 and 50mm focal lengths.
Summary: Without getting into the optical qualities in detail, I can only say that I find the drawing and color properties pleasing. Focus is fast, and the build quality is excellent. Combined with the Pentax K10D, this is my sketchpad -- the kit I carry when I don't carry much.
Summary: Reviewing my travel and other shots, I find that this lens' focal length covers 80% of what I shoot. I have always loved the 35mm focal length for film, and find the 28mm useful. This little 21mm crops to about a 31.5 equivalent, right between the two.
Summary: This was the 2nd Pentax Limited "pancake" lens I've purchased (the 1st was the 40mm). This has probably become my most-used lens! It's always either on my camera or in my pocket for quick retrieval.
Summary: This is a lens I had been considering for use on my K-5 as a moderate wide walkaround for some time. Every time I just about pulled the trigger on it, I would read some so-so review and look at the price and think, no way.
Summary: I've gone sort of nuts buying Pentax lenses for my k5 and kx. I have the 10-17 Fisheye, 15mm Limited, 21mm Limited (sold it), 35 mm Macro Limited, 40 mm Limited, 70 mm Limited, 200mm DA*, 50mm Takumar m42 and just bought the 50mm f1.2 SMCA. I take a lot of events/street, flowers and nature shots.
Summary: This is the perfect lense for walking around and grabbing shots. Easy small and the quality is great. If my main purpose isn't to take pictures but I want to have my camera with me or if I am trying to be more inconspicuous it's the one to have.