Sigma 20mm f/1.8 EX DG RF Aspherical Wide Angle Lens for Canon Digital SLR Cameras
The Sigma 20mm f/1.8 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 degrees. 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. Easy to hold - focusing ring does not rotate during auto-focus, yet it provides adequate focusing torque of the focusing ring during manual focusing of the lensProduct Details
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Customer Reviews
Great for the price
I bought this originally for low light indoor shoots on 40D. Didn't work too well at ISO1600. Turns out, all my other primes Canon 100f2, 50f1.4, 35/f2 are any good either. Of course, zooms only go f2.8, even worse. That made me think it's the 40D, not the lenses. Just went out and shoot in the woods for a day. The results are breathtaking! It blows my Sigma 10-20 and other zooms out of water, maybe with the exception of Canon 70-200/f4L, that is the only exception. Just to be sure it wasn't a fluke, I did some shooting against grass lawn and trees in full sun light. Sure enough, all the zooms except the f4L. I am talking border to border clarity and contrast here! So I am convinced that 40D sensor is the problem at high ISO, not the lens itself. The IQ is especially horrible under low artificial light (the energy saving kind bulbs). At the brighter indoor light situation (e.g. inside Best Buy store), 40D ISO1600 works fine with any lens. But not at home watching TV, or in a Outback Steakhouse restaurant.
Now I've been looking to retire my zooms (with the exception of the f4L) and use primes instead. Just can't find any cheap wider prime like this one though. So I am waiting on my Tokina 11-16 and hoping it'll be better than my Sigma 10-20, as folks are saying out there. That would have been the closest I can get to a uber wide prime. On a crop sensor, 20mm isn't wide enough, especially in the woods.
Until the real revolutionary sensor comes along later on, I'll have to live with the grainy pictures for now. But this prime makes me see things differently for the better. Ironically, I've always held the highest opinion of my Canon 50/f1.4 partly because it is my first prime since I went into photography. After the lawn shoot out test, I realized the f1.4 isn't so great at all, even at f11 at 30'. Maybe my luck on the Sigma is better than on the Canon.
Cheers.
Not bad, but not great
Tried three copies of this lens. Great specifications. Nothing else is this fast at this width and this price. The image is acceptably sharp wide open, but only just -- definitely nothing like Sigma 30mm 1.4, which beats this lens hands down in everything but the width.
Good lens if you are a photojournalist and need to print small images at low resolution. Then pixel sharpness doesn't matter much. But if you are a pixel peeper, beware.
The lens is well built, and looks great, but the motor is noisy and I assume eats up camera batteries.
By far the worst thing about this lens is unpredictable focus, which I encountered on all three copies. None of the copies had any distinct front or back-focusing issues, when focusing on paper. Three out of five times they were spot on. Then they would back or front-focus with equal probability. And yes, I know all about the depth of field and this was not a factor in my tests. And my Sigma 1.4 does not behave like that. As this is an older lens, I think there may be some occasional issues of lens-camera communications that don't exist in the newer 1.4 30 mm.
The bottom line is, I am keeping the first copy of the lens. With all the deficiencies this lens has, I couldn't find any other options at this price. I guess with this lens on, I will have to take more than one picture of everything to make sure I got the shot.
Sigma, how about a newer APS-C version of this lens? Please?
Superfast wide angle at affordable price
This is my fifth Sigma lens, and I couldn't be happier with it. Because of it's f/1.8, don't expect much depth of field when shooting wide open. Especially in close ups, that's the trade off for low light capability. This lens has opened up a whole new world of possibilities for me with indoor photography when a flash is inapppropriate (performances, candids, etc.). The wide angle is not so extreme that I have to deal with distortion at the edges, but in close ups it creates a different perspective on the subject, especially with faces. I also own a 10-20mm zoom which I use primarily for architectural shots, but this is my go-to lens for landscapes, group portraits and low light situations.
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