Sigma 20mm f/1.8 EX DF RF Aspherical Wide Angle Lens for Nikon SLR Cameras

by Sigma

Product Details

• Item Weight: 1.8 pounds
• Shipping Weight: 2 pounds (View shipping rates and policies)
• Shipping: This item is also available for shipping to select countries outside the U.S.
• ASIN: B00005RKSL
• Item model number: B00005RKSL
• Average Customer Review: 4.5 out of 5 stars  See all reviews (27 customer reviews)
• Date first available at Amazon.com: November 1, 2001

Product Description

Style: Nikon SLR Cameras

Amazon.com Product Description

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 autofocus. At the same time, however, 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, aspherical lens elements in the front and rear lens groups to compensate for distortion and spherical aberration, and a 94.5-degree angle of view.

Specifications

• Focal length: 20mm
• Maximum aperture: f/1.8
• Lens construction: 13 elements in 11 groups
• Angle of view: 94.5 degrees
• Number of diaphragm blades: 9
• Minimum aperture: f/22
• Minimum focusing distance: 7.9 inches
• Maximum magnification: 1:4
• Filter size: 82mm
• Mount: Nikon
• Dimensions: 3.5 inches in diameter and 3.5 inches long
• Weight: 18.3 ounces
• Warranty: 1 year

Product Description

Sigma 20mm f1.8 EX DG Aspherical RF is one of several EX Series lenses. It is the first 20mm Super wide-angle lens in the world with a large aperture of F1.8 and angle of view 94.5°. It has Macro focusing capability with a minimum focusing distance of 20cm/7.9inches (reproduction ratio 1:4). The iris diaphragm has 9 diaphragm blades to obtain beautiful out of focus image. It incorporates an aspherical lens element in the front as well as rear lens groups, to minimize distortion, spherical aberration and astigmatism. The lens has non-vignetting optical construction, in order to obtain adequate peripheral brightness with open aperture. This is especially desirable for digital cameras. The lens incorporates a rear focus system eliminating front lens rotation, thus allowing the use of a Perfect Hood and easy use of polarizing filters. The lens also incorporates dual-focus 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 lens materials used in this lens are lead and arsenic free ecological glass.

Customer Reviews

Most Helpful Customer Reviews

34 of 37 people found the following review helpful:

5.0 out of 5 stars AMAZINGLY SHARP AND FAST SUPER-WIDE ANGLE, May 7, 2006

By 

Canon "Rock" (United States) - See all my reviews

This review is from: Sigma 20mm f/1.8 EX DG RF Aspherical Wide Angle Lens for Canon Digital SLR Cameras (Electronics)

I have used this lens extensively with the 1D and the Rebel XT. Results have been excellent. My suspicion is that the previous reviewer got a defective or damaged copy of the lens. It is incredibly sharp, even at f1.8, which I did not expect - generally you expect a lens to be a bit soft wide open, especially 1.8. The degree of sharpness of this lens is quite surprising.

I have used, for example, both the Canon 50mm f1.8 and the Canon 35mm f2.0, both of which are deservedly renowned for their sharpness and contrast. I find this lens to be sharper than either of them wide open. The lens provides images which have excellent color saturation and contrast. Of course, at f1.8, depth of field is razor thin, by design, which is great for bokeh or out of focus background, but which also requires care concerning the desired focal point being in focus. Speaking of bokeh, I find it to be very attractive compared to any other lens I have used.

Its minimum distance focusing is also quite remarkable. I think it is rated at just under 8 inches, but I routinely focus at distances which seem a good bit closer than that. The lens works well as a macro for many applications, with a relatively strong multiplication factor.

Of course, given the inherent light-gathering of a 20mm focal length lens, combined with a huge aperture of f1.8, this lens is outstanding for shooting indoors or in other low-light situations with natural light and no flash.

Canon's nearest competitor to this lens is the 20mm f2.8, which is a full stop slower in terms of light collection. I consider this lens to be an extremely good value at the retail price, new. If you can get a good copy used on-line, it will be an incredible value. You may find that you never want to take the lens off the camera because of its versatility as a walkaround lens.

This lens has been extremely well-reviewed, by and large, on lens forum sites. I encourage you to check those out. Most people rate the lens 5 out of 5. A distinct minority give it 1 out of 5. I suspect that they either have defective copies which may need repair, or they have inaccurate perceptions of the lens. Also, popular photography magazine online reviewed this lens, as well as the 24 f1.8 and the 28 f1.8, very highly.

I would highly recommend this lens to anyone who wants a fast, sharp superwide angle lens.

11 of 11 people found the following review helpful:

5.0 out of 5 stars Ultra-wide lens with sharpest optics!, June 5, 2004

By 

Denzil Thakur (Dubai, UAE) - See all my reviews

Sigma 20mm EX is an exceptionally well made lens. Performance is extremely satisfactory. It is almost indispensable for me to go without it when I am outdoors. Takes very good wide angle shots of buildings, parks and friends and family picnicking in the park. Shots have come very sharp and crisp with edge to edge brightness and sharpness. 20mm wide angle focal length gives you a very large depth of field which is essential for taking shots of wide open outdoors, filling your frame with a large expanse of ground/sky. Fast f1.8 aperture will let you take snaps indoors in natural light and hand-held shots of lighted buildings etc. in night time. Rear focusing feature of this lens results in fast AF and also the length of the lens remains same. Macro shots of subjects will give you convex mirror type of fascinating images and one can produce far more interesting effects depending on one's creativity.

Indoor flash photography may give rise to vignetting due to ultra wide nature of the lens as most flashes cover only 28mm span. This may probably be solved by using a wide angle attachment on the flash which to my disappointment was not available for my flash (Pentax AF-280T). Also 82mm filters may prove to be expensive. But I think a filter is essential for this lens as the front element glass is very near to the filter area.

All said this is an extremely satisfying buy (most bang for bucks) which gives you great results.

9 of 9 people found the following review helpful:

5.0 out of 5 stars Sigma 20 mm for Astrophotography, August 16, 2010

By 

JoLo - See all my reviews

Amazon Verified Purchase

This review is from: Sigma 20mm f/1.8 EX DG RF Aspherical Wide Angle Lens for Canon Digital SLR Cameras (Electronics)

I purchased the Sigma 20mm f/1.8 lens, mainly for wide field astrophotography purposes. I refuse to pay what Canon was asking for a comparable lens...this Sigma lens costs less than half of what Canon charges. I can tell you the quality is top notch - well built, very sharp images across the field, easy to use and transport. The two issues I knew about before purchase - the autofocus is a bit rough and noisy compared to the Canon and you have to engage the focus ring for manual focussing - were no surprise, and really not much in the way of issues anyway. The autofocus with the Sigma is a bit noisier than the smooth Canon lens, and is remembering to move the focus ring when manually focusing really a hassle? Some reviewers made it sound horrible, but for saving over $500 I will put up with a little noise and a focus ring......

I captured some fanstastic shots of the Perseid meteor shower while camping at Joshua Tree in early August - the Sigma performed flawlessly. I recommend this lens without reservation.

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