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.
Canon @ 5:46 am
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.
Denzil Thakur @ 5:56 am
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.
Micah @ 7:43 am
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 an inch of the front lens element! [edit: re-checked and it's actually about 3" from the front element. For reference the Nikon 20/2.8 focuses about 9" and the 28/1.4 focuses about 11" from the end of the lens.]
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. [edit: ok, maybe I can complain. It took them no less than five (5) tries to repair it properly. But in the end they did and I only had to pay the cost of shipping the first time. Works at least as good as new.]
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.
[edit: falling in love all over again! This thing rocks on my new d700!]
William B. Newkirk @ 9:51 am
If you want to take indoor shots with your SLR, this lens will let in enough light to stop the action. It also will work on your film camera for those REALLY wide-angle shots. I typically use prime lenses for shooting indoor shots and this is one of the best, because of the wide angle (30mm equivalent), sharpness, and speed. No other wide lens has the speed of this one (f1.8). I have taken shots in DIM light without flash that have come out great. My best 3 lenses for indoors are this one, a Pentax 35mm F2.0, and a Pentax 50mm F1.4. I have a Sigma 28mm F1.8, but it is not as sharp or useful as this one. The only drawbacks are the size and the cost of a filter that fits this (82mm filters are NOT cheap).
Chris B. @ 12:32 pm
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.