Quote: NaClH2O: I'm looking for a constant aperture zoom lens in the wide angle to "normal" range. When I got my K20D I gave my K10D body and the two "kit" lenses (along with some other stuff) to my brother-in-law. I now find I'm looking for a replacement for the 18-55. My requirements are:
1) constant aperture
2) no more than a 4X zoom
3) wide end around 16-18mm
4) auto aperture
A little over a year ago, when I found myself in this position, I opted to go with the Tamron 17-50. I spent a lot of time reading reviews by owners of the lens and was amazed by what I was reading. Back then the lens was only emerging in Pentax mount, so I relied on Canon & Nikon owners' accounts of the Tamron. It was impressive just how much they loved the lens, many of them saying it performed with or outperformed the much more expensive Canon & Nikon counterparts. And outside of owners' reviews, the lens got impressive numbers in the testing labs.
What is a treat is the lens' performance wide open--why else buy a 2.8 lens? And starting @ 3.2 on down the lens just gets better all the way until diffraction issues set in. It also has great performance to the edges. I have yet to do it, but have to believe it will produce beautifully at extra large print sizes--a perfect companion for the K20 & K7 if you have this goal in mind.
You own the 28-75 brother and I perfectly understand why you would consider carrying overlap. I too am considering picking up the 28-75 mainly because I would love its longer reach & f2.8 for indoors. That lens is known for great performance. Trouble is, I just picked up the Sigma 10-20 and now I really have to make some choices.