Technical Details
- Lens Construction: 13 Elements in 11 Groups Angle of View: 94.5 degrees Number of Diaphragm Blades:
Product Description
This super-wide-angle 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 optimized Digital SLR camera.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, thus 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.
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
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Customer Reviews
"very nice lens" 2009-07-23By
Kerry Pierce (Detroit, MI USA)
I recently purchased this lens, so I don't have a lot of shutter time with it yet, but thus 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 . 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.
"Sounds good on paper AND in real life" 2009-07-04By
F. LeungI really can't fault this lens for what it is not - after considering its modest price tag. Sure it's not a Canon 24/1.4L and it's not exactly sharp wide open on a full-frame DSLR. For less than $300, however, its few shortcomings (AF clutch design, AF speed/accuracy) become just minor inconveniences and you get a great lens for available light environmental portraits. My copy provides useable 8x10" prints at F/1.8 and is very sharp by F/3.5. Flare control, contrast and color rendition are fine. Bokeh and macro performance are surprisingly good for a wide angle. All in all, I'm glad I didn't spend a lot more (in these tough times) to own the 24/1.4L.
"A bargain for digital SLR users" 2009-04-15By
M. Puckett (Arlington, VA United States)
This was almost always the lens of choice for me on my Sony Alpha A100. I cannot comment on it's capibilities for full-frame cameras, but for almost all Sony/Minolta digital users, this will not be an issue anyway. The 1.8 aperture, combined with Sony's anti-shake feature allow for some really nice low-light photography.
It worked equally well for candid portaits and any kind of landscape photos on the Sony, I was surprised how much wider it felt than the standard 24-xx mm zoom lenses, and the quality was always miles ahead.
Downside: not the fastest focusing, and IQ in low light is not that great; it does tend to hunt for the correct focus. Not sure how much of that is the camera, and how much is the lens. Also, be prepared to get the lens focus calibrated in order to bring out the best from it.
Overall, great sharpness, color and contrast for the price.
"Bulky but very useful for available-light shooting" 2009-01-08By
Chris B. (St. Paul, MN USA)
I had been using a Pentax-M 50mm f/1.4 and loved the ability to shoot in low light. However, the -M lenses are manual focus and manual aperture, and I was getting too many out-of-focus shots that I regretted missing (I'm taking a lot of baby shots lately). So I decided to get a full-auto fast prime, and I was looking at this and it's 24mm and 28mm cousins.
The lens works beautifully. It's a tank and feels well-built. Not as tight as an all-metal lens, but solid nonetheless. If you note, the 20mm doesn't have a macro mode - the 24mm and 28mm do. Really, it focuses very close without any problems, but at this focal length it's kind of silly to be thinking 'macro photography' anyway.
The 30mm effective focal length is a tad wide even for indoor close-quarters shots. If I had to decide again, I'd probably opt for the 24mm or possibly even the 28mm - the effective focal lengths would be a little more practical for my purposes. However, if you want to take in a lot of scenery and need a fast lens, this fits the bill without venturing into the fisheye territory.
Optically, I was disappointed at first, because I was getting soft pictures when it's wide open, even when on a tripod. But then I did a focus test and found my camera was back-focusing. I have a K10D, so you have to do some trickery to adjust the focus (search online and you can find out how), but afterward, I'm getting acceptably sharp images.
And, for the record, my camera says the aperture opens to f/1.7 - not that I'm complaining.
I give it just 4 stars, though, because when compared with my Pentax-M 50mm f/1.4 when they're both wide-open, the old 50mm is noticeably sharper. From what I've heard, you have to spend the cash for one of the Pentax limited lenses to get the same quality in an auto focus lens as with their old -M and -A glass. So, for about half the price of a limited lens, you're getting a good deal.
"Fantastic bokeh" 2008-11-03By
M. Heinrich (Beaverton, OR USA)
I picked this up just over a month ago when I got my D90. It has been on my camera more than my 18-200mm VR. I truly love this lens. The bokeh is amazing. It is a touch soft but that is easily fixed with software. The low light shots always surprise me on how well they look even over my Nikon 50mm 1.8. This is one lens I will not regret buying.
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