Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- User Rating: 
Summary for Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- great value
Notes on Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- Although I liked the reach of the kit lens more, now that I have the 50 f1.4 I felt that this sigma would fill the wide end better than the kit. Besides the weight and large diameter (which makes me adjust the walls in my bag a bit to get it to fit), I can't fault this lens. It has been very sharp, has good contrast and the flare resistance has been solid. One thing that is nice is that manual focus is still possible even with the lens hood backwards (sometimes if I'm in a hurry and just pulled the cam out of the bag, the hood will be on backwards for storage). I've also noticed that this lens will allow for some pretty close focusing - around 4 inches from the front of the lens at 35mm.
Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- User Rating: 
Summary for Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- Pretty darn good
Notes on Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- Purchased this lense a month ago. It is a bit heavy but overall it takes good pics. Glass is decent and speed is pretty good. It worked for me well in indoor and outdoor shooting conditions. For the money I think its a good buy.
Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- User Rating: Summary for Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- Great Lens
Notes on Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- This lens is as sharp as they come. Great for low light shooting wide open.
Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- User Rating: Summary for Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- great lens
Notes on Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- Great deal. It is a bit bulky, but it is not heavy at all. Very sharp when stopped down, but soft F2.8 has many applications. I am not using my SMC 21mm (limited) anymore, since this lens is sharper at 21mm setting and even more sharp at 17mm.
Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- User Rating: Summary for Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- Great Bargain
Notes on Sigma 17-35mm f/2.8-4 EX DG IF Aspherical ...- Pros:
Center Sharpness
Flare Resistance
Chromatic Aberration (CA) Control
Aperture Ring
Quality
Cons:
Some distortion from 17-20mm, (noticeable on architecture)
Slightly soft corners (still very usable)
Size (it is huge)
Who should buy this lens? Anyone looking for a great deal in a wide angle lens. Just be aware there are two versions, this current version and an older version. The one I bought through Cameta is the new version. Be careful buying used copies because the older version is no good. The picture shows the older lens, the new lens does not have the AF-MF switch, and it adds an aperture ring. It also no longer has the clear window for the focus numbers, they are just printed on the barrel.
The build quality is excellent considering the plastic construction. The first thing you see when you open the box is a high quality nylon web bag with a high quality zipper on it (and a belt loop). You open the bag and there is high density foam backing to protect the mount side of the lens. However, I noticed how large this thing is. It is a monster, easily 4 times the volume of a 21mm Ltd pancake. Many of you will like the built in aperture ring.
I was actually surprised at how well the sigma performed. It had excellent center sharpness, but slightly soft at the extreme corners (still very usable though). It provides excellent chromatic aberration (CA) control and flare resistance. At the wide end of 17mm it was also surprisingly good, but had a little distortion, but significantly less than the Pentax kit lens (version 1). By 21mm the distortion was mostly gone. The bokeh can be a little hectic, sometimes providing a double or ghosted image of the out of focus object.
The Sigma is a great value, and if you are on a tight budget it would make an excellent lens. I would have liked to compare it to the kit lens at 21mm, which I no longer have to see if it is worth the upgrade. My guess is that it is better than the kit lens in the focal lengths it covers, but I can't say that with much certainty. The lens has a nice sharp image, and excellent control of CA. Great value.
UPDATE: The difference between version 1 and version 2 for the Pentax mount is actually the model designation, EX is the first version and EX DG is the second version. You want to get the EX DG lens. It comes in a black case and also says EX DG on the lens, the older version says EX only and comes in a green case.
