Sigma 170-500mm f/5-6.3 DG APO
(From Sigma lens literature) This compact ultra telephoto zoom lens covers a range up to 500mm and optimized for digital SLR cameras. The new multi-layer lens coating and lens design reduces flare and ghosting. This lens uses one aspherical lens and three SLD (Special Low Dispersion) glass elements for excellent correction all types of aberration, resulting in better picture quality on both film and digital SLRs.
The new multi-layer lens coating and lens design reduces flare and ghosting, and creates an optimum color balance through the entire zoom range
This compact ultra telephoto zoom lens covers a useful range up to 500mm and it is ideal for sports, nature, wildlife, and landscape photography. It lets you bring your far away subject up close.
The five-group zoom and rear focus systems ensure high performance stability and ease of use. Since the front of the lens does not rotate, a circular polarizing filter can be easily attached and use.
A zoom hood is supplied with this lens to prevent flare and ghosting as well as extraneous light harmful for image quality. A removable tripod collar is also included as a standard component.
Sigma 170-500mm f/5-6.3 DG APO
Sigma 170-500mm f/5-6.3 DG APO User Reviews
8 out of 10 points and recommended by Solutionsetcetera (5 reviews)Sharp, long, and inexpensive.Lens creeps quite easily and is a bit clumsey.
This lens is an older design, recently updated with Sigma's DG coatings for better flare/reflection control for DSLRs. When researching to see if this lens was right for me, I read many comments about it being soft and slow to focus... but I had seen far too many photos taken with it that would indicate that this was not the case.reviewed December 29th, 2006 (purchased for $679)
Before purchasing, I had the opportunity to shoot this lens along with the Sigma 50-500 and 80-400 OS, the Nikon 80-400 VR and 300 AF-S f/4, and the Tokina 80-400. I saw no significant difference between the Sigma and Nikon zooms. Yes the OS/VR models are a big advantage for hand held shots, but no match for a good tripod. And I felt it was sharper with better color rendition than the Tokina. However the 300mm Nikon prime was noticeably better in all respects, especially it's amazing resolution and CA control. But back to the lens at hand.
If your looking for a big tele-zoom and have the up to 200mm range covered with other glass this lens is an excellent value. If you don't, you may wish to consider the $300+ pricer 50-500mm or the OS/VR models. My biggest complaint of the 170-500mm is it creeps easily when pointed straight up or down, and really would be easier to carry/handle with a focal length lock.
As far as sharpness is concerned, this lens is as capable of sharp shots as the other tele-zooms, but keep in mind this pup is the equivalent of 750mm FOV on APS-C sensors and your tripod and head/mount better be up to it. Mine wasn't, and camera movement induced by mirror slap made for unsharp shots at 500mm. This was far less noticeable on my film body so it is that extra 250mm that is really going to test your support system. At high shutter speeds (1/750th and up) this is not such an issue.
The supplied tripod collar is well designed and very solid... oddly enough better than that of the much pricier Nikons mentioned above.
In good light autofocus is as good as any screw drive lens, but it can definitely hunt in low light. If you have enough light to hand hold this lens, focus speed will not be much of an issue.
At best this lens is a compromise. If your looking to go walking about you will do well to consider one of the 80-400 OS/VR offerings as the 170-500 is a bit clumsy and will need the brightest of light for hand held shots. However if you want as much reach as possible from a good tripod its bang for the buck is hard to ignore.