Review on Pentax 16-45mm f/4.0 SMC PDA ED AL Zoom Lens: Compatible with Pentax and Samsung Digital SLR Cameras by Brenda Thompson

I've been using this lens for almost a year and have taken hundreds of photos with it. I usually have it on K10D with a circular polarizer. There are many pros and some cons: Pros: 1) It's significantly lighter and smaller than you would expect from a constant f4 lens, given that it's designed for DSLRs. You can leave it on the camera as a "regular" or "road" lens for walking. 2) Image quality is excellent from center to corners, even at f4. I have an 18-55 kit lens and the difference in image quality is obvious at f5.6 but less so at f8 and smaller. 3) An excellent travel lens at its widest focal length of 16mm, especially when combined with a polarizer for landscapes, cityscapes, etc. Although the Pentax K10D has a built-in shake reduction system, it is advisable to use a tripod with a bubble level, to make sure the horizon is even (unless you want to fix them in Photoshop!) 4) It's a lot cheaper than 16-50/f2.8 (which could be a bit better) Cons: 1) Don't use the built-in pop-up flash with this lens on wide-angle lenses. Corner Position - You will see a black semi-circle in the lower half of the image. You must use a hot shoe or an external flash. 2) While it's quite light and performs better, it's a bit heavier than the cheaper 18-55 kit lens (which is only 2mm longer at the short end). and 10mm longer at the long end)3) If you can afford it, the 16-50/f2.8 might be a bit better, it's also weatherproof (K10D is weatherproof, 16-45 isn't). - don't shoot in the rain) and has a larger maximum aperture (better for low light shooting, emphasizing objects in the foreground) 4) 45mm is sometimes short, and maybe 17-70 is better if you catch yourself doing it often shoot portraits5) If you only need one lens when traveling, sometimes an 18-250 lens is preferable (long zoom helps to compress foreground and distant subjects and avoids "zooming with your feet"), although there isn't any Wide angle constant would have aperture and more limited in the wide angle department.