Sigma 15-30mm f/3.5-4.5 EX Aspherical DG DF

Great wide angle lens This is one of the sharpest lenses I've used. Great contrast, excellent edge sharpness, both on APS-C and full frame. The one downfall of this lens is the focus drive. It's fairly loud, and slower than Canon USM or Nikon SW systems, but if you shoot wide angle, you're most likely not concerned with that. Sharpness is very close, if not better than the Canon 17-40mm f/4 L. Filter attachment is a little weird with the "filter hood" that goes over the built in hood. I've also had the lens show light flares, but good practice makes this avoidable. Overall, and excellent value for a sharp wide angle lens. The few drawbacks don't take away from the sharpness or build quality.

Sigma 15-30mm f/3.5-4.5 EX Aspherical DG - Nikon This review is based on sample of one in late 2010. I have been an avid photographer on film and digital, but not a pixel peeper; for the amount paid, this lens is more than I expected. Good: super-wide FX on Nikon D700. Great details on center and some corners. Color rendition is fine. Bad: Not able to get sharp results on one corner at infinity focus, doesn't matter what the setting is. Sigma quality control issues are well known, lens possibly de-centered. I decided to keep this purchase for interior and architecture shots where close in and medium distance renditions are important. There are not too many economical alternatives any way.

Sigma 15-30 is a very good value I purchased the Sigma 15-30 zoom specifically for use on a digital SLR, so most of my photos will be taken in the sweet-spot in the center of the image. I prefer zooms on digital SLRs because changing lenses creates a dust problem with them, so the less you have to change them the less often you have to clean. The sensors are remarkably easy to damage, so any cleaning is a risk. I have tested it with both Digital and Still cameras and the results are really quite good; even in the corners of full frame 35mm film. Yes, there is some barrel distortion at 15mm, especially with full frame 35mm photos, but it is quite acceptable. Now that Adobe Photoshop allows distortion correction it is very easy to correct. The effect is less noticable on my 1.5:1 digital, and for most uses isn't noticable. Sharpness and color correction are alot better than I expected. I'm not talking about perspective distortion - that just goes with the territory very wide angle lenses. I have been a professional photographer for a lot of years and I am very satisfied with the images. I've gotten worse from non-zoom lenses in the 15-21mm range; and paid a lot more for them. It isn't up to the quality of my fixed focus 15mm Nikkor, but very few ultra-wide lenses are. It will produce a professional quality image, with a lot more versatility than a fixed focal length lens, and that's what counts. I haven't carried the 15 Nikkor for a while unless I'm specifically shooting architecture on film, not digital. Mechanically the lens is smooth in operation with good feedback and no slop in the zoom or focus. It is also remarkably light weight but seems very durable. All-in-all a remarkable piece of optics for the money.