Sigma 20mm f 1.8

Sigma 20mm f/1.8 EX DG The Sigma 20mm super-wide-angle lens provides minimal light falloff and superior peripheral brightness, helping you take masterful landscape shots or large family portraits. The lens is equipped with a high-quality Dual-Focus (DF) mechanism. The DF system makes it easy to hold the lens, as the focusing ring doesn't rotate during

Lens with and without petal-type hood

autofocus. At the same time, the lens still provides adequate torque for manual focusing operations. By incorporating a rear focusing system, Sigma made the lens compatible with petal-type hoods, which offer superior light blocking effects. In addition, the lens offers a super multi coating that reduces the flare and ghosting that often occurs in digital cameras, along with nine diaphragm blades to help you obtain beautiful out-of-focus images in the foreground and background. Other features include a minimum focusing distance of 7.9 inches, a maximum magnification ratio of 1:4, asphericall lens elements in the front and rear lens groups to compensate for distortion and spherical aberration, and a 94.5-degree angle of view.

This super-wide-angle prime lens is ensured minimal light-fall-off with superior peripheral brightness. The iris diaphragm has 9 diaphragm blades to obtain beautiful out of focus images in the foreground and background. This is an ideal DG lens (also works on 35mm SLR and full frame cameras but is optimized for Digital SLR cameras). The minimum focusing distance of this lens is 20cm (7.9 inch) and it has maximum magnification of 1: 4 with fast F/1.8 maximum aperture. The minimum focusing distance of 20cm (7.9 inch) and 94.5° angle of view allow close up photography surrounding the photographic subject. The lens incorporates Dual-Focus (DF) mechanism. It is easy to hold the lens, since the focusing ring does not rotate during auto-focus, yet it provides adequate focusing torque of the focusing ring during manual focusing of the lens. The rear focus system eliminates the need for the front of the lens to rotate, As a result allowing the use of a "Petal-type hood", which is superior light blocking effect. The use of aspherical lens elements in both of the front and rear lens groups effectively compensates for distortion, spherical aberration and astigmatism.

very nice lens, July 22, 2009

By Kerry Pierce "kerrypierce" (Detroit, MI USA)

I recently purchased this lens, so I don't have a lot of shutter time with it yet, but As a result far, I'm very pleased with it. I use the lens on both a Nikon d300 and a Nikon d700.

I was pleasantly surprised to see that the lens is quite sharp wide open, at f/1.8. Stopped down to f/4 or f/5.6, the lens is very sharp, at least in the center. I haven't tested edge or corner sharpness yet.

The lens is large, typical Sigma style, but good build and finish, also typical of the Sigma EX lenses.

Overall, I'm quite pleased with the lens. It works well on both of my cameras and produces sharp photos with good color and contrast.

I have 2 issues with the lens. Autofocus is rather slow and the lens switch for manual/autofocus is the focus ring. The focus ring is very large, taking up most of the lens barrel. That's a clever design and is nice if you do a lot of switching between manual and autofocus, because you don't have to look at the lens to find the little switch like you do on most lenses. But, that design is also a problem in that it makes mounting the lens on the camera more difficult to do without moving the focus ring to the Manual position. Neither of these things are show stoppers, so I think the lens rates 4 stars.

By Micah

This is one of my all time favorite lenses. I usually just leave it mounted. It's fast max aperture and close focusing make it indispensable to me. Check it out--it focuses to within and inch of the front lens element!

I've had one issue-it recently self destructed. The iris folded over itself. It's inside the four year warranty (and damn near the end I might add) so it's been fixed and is currently on the way back to me from sigma as I type this. I'm disappointed it failed, but considering the frame count and price, I can't really complain.

I paid not much more than $300 for this lens new almost 4 years ago, and I'd gladly pay twice that for the shots this lens has gotten me. I've taken it out in the rain and snow and hail and the fact that it failed only recently attests to the build of this fine lens.

Buy it while they still make it! I may buy a backup soon for this reason