Summary: This lens is great step-up option from the Kit Lens, and offers a reasonably bright constant aperture of f4.0. Iv'e even used this lense wide open at indoor concerts/plays with good results. As a 'standard' zoom, this lense serves admirably, at a 35mm equivalent of 24-68mm focal lengths. It is reasonably light for a quality optic, and offers the Pentaxian a 'quick-shift' clutch mechanism to easily shift back and forth from AF to MF.
Pros: Sharp, even wide open, famous Pentax multicoating, and anti-ghosting formula for improved digital performance. Nice lense hood with window feature to facilitate use of a rotating circular polarizer. (Never leave home without one!) Amazingly, this lense holds it's own against prime lenses at just 1/2 stop from wide open. I have not done extensive testing, but this is a fine optic. Images shot on my Ds can easily be interpolated to 150% without any noticeable pixelation...
Cons: A bit long & on the chunky side (67mm filter size) and a tad hefty, but compared to any f2.8 standard zoom, (usually 77mm filter) this lens is very manageable. Hey, there's always a tradeoff. Slight back-focus issue noticed in AF low-light, wide aperture conditions, but I usually shoot in MF, so this almost never is an issue.
Summary: Before buing it I read much good about this lens. Almost everywhere it is praised for its optical characteristics, price, and build quality. Personally, I bought it because there was nothing else on offer. (Hopefully, the new Pentax announced real star lens is comming soon.) I agree that optically it is a very good tool. It is sharp and, what is much more important, distortions are quite well controlled. I also fully agree that its pricing is very good.
Pros: Sharpness., Minimum distortions., Price.
Cons: Build quality is OK (good for the price, though).
Summary: A constant aperture zoom which is a very big step up from the kit lens.
Pros: Constant aperture, much sharper than a zoom has any right to be (am I showing my age here?), well-balanced and very little distortion for a zoom. In fact, lower distortion than a lot of primes!! (my age again?)., Of course, it's not cheap. But you definitely get what you pay for!, A crisp, strong lens with very little flare. That SMC coating is impressive!
Cons: I will replace it with the 16-50 f/2.8 eventually, when it is released. I find f/4 hard on the old eyes., For those who care, the lens casts a shadow with the on-camera flash below 28mm.
Summary: Initially I debated months due to its size and weight. That has turned out to be an absolute non issue. It does weight a tad more than the 18-55 Kit lens, but it focuses instantly - no hunting. just locks on, and is razor sharp. The size and balance is actually very pleasing on my K100D, a bit longer and larger in the barrel, especially with the 70mm primary lens, which appears massive when compared again with the 18-55 Kit.
Pros: Everything - a solid instrument.
Cons: Nothing, other than it does not come with a lens bag. The 10-17 came with one, which I find to be a very nice touch, especially in use. I believe that all the lenses should come with their very own bag/case.
Summary: A very good lens for the price. The optical characteristics are good: 1. Flare resistance outstanding! 2. Distortions are low. Especially, when compared to similar products from other manufacturers. For example, Canon 17-40/4 L is more than twice as expensive, but distorts the image more at the widest setting, as on-line tests show. I guess, the price difference is due to the fact that the Canon lens is dedicated to a larger full-sized sensor.
Pros: Very good optics.
Cons: I would agree to spend more for a full metal construction.