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Sigma EX 20mm 1:1.8 DG Aspherical
My sample is an optically extraordinary ultrawide-prime for "fullframe" from Sigmas high-end "EX" series, but without HSM. At least the micro-motor doesn't always breaks down any more, like the first HSMs did.
Have I ever talked about sample variation? This sample of this lens is the proof for what and where Sigma could be, if there were none. I have tested this lens a few times in the past and it was really really crappy: A bit like a plastic toy lens, with an "a-bit-less-soft" center and complete mush just outside the inner circle - at least wide open. Stopped down, it improved dramatically to "just the worst lens I know". Reading the reviews on the net, this exactly seems to be the usual performance of this lens: Crap. But nonetheless I have always found the concept funny: An ultrawide that, like ultrawides do, exaggerates perspective, the relations between near and far, when you get close, combined with an ultrafast aperture, making it possible to additional blur that background, regardless of the huge depth-of-field, the angle of view provides by itself. So it can be even more dramatic, because not only the background vanishes, but it also fades away from sharpness. And now, really, I "accidently" bought one on ebay. It was one of those buys: I bid an amount, that's normally completely impossible to win an auction at for the specific item, but for which I'd simply have to take it on the other hand, because I could always resell it with a huge profit, if I'd want or need to and so low, that it's no pain to have to pay it in the first place. It's a bit like playing the lottery, but without any cost for the ticket: Chances are minimal, because normally auctions end at prices around 100,- €, but if the auction ends in an hour and it's at 5,- now, why not bid 10,-? I quite often bid such absurd low amounts and really have been lucky, maybe one out of 1.000 times, like with my 180/2.8 Macro ... and now with this 20/1.8. It was originally for Sigma mount, but that's only about 20min of soldering to change it to Canon and I had a perfectly fitting bajonet mount from a broken 18-125mm lying around, which I have bought for parts.
And when I tested it ... I finally knew, what sample variation is.
Sadly, it needs 82mm filters. It has an OK distortion-characteristics, vignets a bit and is well built.
It sells for between € 250,- and 400,- on ebay in Canon mount, which is quite a lot, but well below € 200,- in Sigma - mount, which is trivial to convert.
Oh... did I say, that I have always found the concept cool? This Sigma is truly unique. I have thought a while about how to describe best, what makes it so special and the best way I can do is to say that it feels like a "macro ultrawide", because it focusses so close that objects in focus nearly touch the lens and at f/1.8 depth-of-field, despite the extreme 20mm field of view is so shallow, that you really get this "tele-macro" look, that you get with a 180mm lens at 1:1, only with the ultrawide perspective. Cool, really!
COMPATIBILITY
As a classic EF - lens, it mounts on every EOS - body ever made, be it 35mm film, APS, digital APS-C or "fullframe". On APS-C, the smaller sensor of these cameras let's this lens have an angle of view like a 32mm-lens would have on 35mm.
Warning: There's always potential compatibility-issues with third-party lenses and newer bodies and this has happened to Sigma - products more than once in the past, so that I personally rate this risk as high. But keep the price in mind when judging this risk.
PRICE
Prices vary quite a bit. For Canon - mount versions, it's between € 250,- and 400,- in my experience and below € 200,- for Sigma mounts.
ACCESSORIES
I own the included shade, but don't use it. It was shipped with a pouch of very nice quality, I don't use too, because the lens is very compact and easily fits in my normal bags.
It uses 82mm, but I don't use it with filters because of it's "macro ultrawide" characteristics, where filters aren't needed. The filter-thread does not rotate. A 82-77 step-down ring vignets heavily.
MECHANICS
Made in Japan.
Metal lens mount.
Mostly made of metal.
This is a Sigma - pro-grade - lens from the first era after they startet calling their expensive lenses "EX". It meets higher standards than the cheap models regarding materials, built-quality and tolerances and while still a bit cheaper made than e.g. the 15-30mm and nowhere near Canons L-lenses, it's a whole class above e.g. the first version of the 17-35 with 82mm filters. The finish is a bit of a problem. While not as nasty as the old rubber-style-coating that turns into glue over the years and more durable durable than on the old version, it still has some potential to get ugly and look worn when it scratches and comes off, you can sometimes scratch it off with a fingernail.
The lens is medium sized, about as big as a compact ultrawide zoom like the 17-35.
It uses a conventional micro-motor for focus, which is loud and slow, but that hardly matters in an ultrawide-lens and it at least doesn't break down. AF accuracy is fine on all of my bodies, what's quite unusual for Sigma-lenses, especially for newer ones.
During automatic focussing, the focus ring can be detached, but you still have to turn a switch, too. The focus clutch is quite a good idea on Nikon, where you detach the camera-motor with it, but crap on Canon, because you have to change to switches.
The manual focus-ring feels solid and even a bit damped. Focussing is internal (achieved by moving the back element), so nothing moves.
All in all a quite solid and on a standard probably even good enough for pro use, but not Canon L standard.
ERGONOMICS
Great. It feels light and small, but still solid. Size DOES matter, also see Lenses: What's important?. I hold it right intuitively, gripping it exactly right to focus. The focus-ring is in the right position to grab it anytime. The damped MF feels great.
You can hold a body with this lens in one hand. It fits in my usual bags.
There is a focus-scale behind a window without infrared-focus-indices but with a depth-of-field-scale.
The two-switch AF/MF change is miserable.
It takes 82mm filters and a 82-77 step down ring vignets heavily.
Overall: Good but not great.
OPTICS
Optics of this Sigma, at least of my sample, are very good. This indeed seems to be a matter of sample variation, as all reviews on the net find it to be extremely bad. And I have tested this lens a few times in the past myself and it was really really crappy: A bit like a plastic toy lens, with an "a-bit-less-soft" center and complete mush just outside the inner circle - at least wide open. Stopped down, it improved dramatically to "just the worst lens I know". Reading the reviews on the net, this exactly seems to be the usual performance of this lens: Crap. But nonetheless I have always found the concept funny: An ultrawide that, like ultrawides do, exaggerates perspective, the relations between near and far, when you get close, combined with an ultrafast aperture, making it possible to additional blur that background, regardless of the huge depth-of-field, the angle of view provides by itself. So it can be even more dramatic, because not only the background vanishes, but it also fades away from sharpness.
Oh... did I say, that I have always found the concept cool? This Sigma is truly unique. I have thought a while about how to describe best, what makes it so special and the best way I can do is to say that it feels like a "macro ultrawide", because it focusses so close that objects in focus nearly touch the lens and at f/1.8 depth-of-field, despite the extreme 20mm field of view is so shallow, that you really get this "tele-macro" look, that you get with a 180mm lens at 1:1, only with the ultrawide perspective. Cool, really! This is, what you can do with this lens and completely ordinary objects (it's all stuff that's scattered across my "working" (or better: playing) room) - and only with this one and only lens:
And some nature-shots, all at f/1.8 and very close, even if most not at MFD, which is so close with this lens, that it gets really hard to compose a shot:
The minimum focus distance is 0.2m, which is simply extraordinary.
I expected distortion to be massive in absolute terms because of the quite extreme 20mm, but better than ultrawide-zooms, simply because it's a prime - and that's exactly what it is. And it is even better than most standard-zooms, but for architecture, you'd still have to correct distortion. I didn't test this in-depth, but my test-shots seem to show quite uniform, easy to correct distortion-characteristics.
The plane of focus is very flat for an ultrawide, only very slightly curved outwards, so you have to focus a little bit closer to get the corners in best focus. This is better than most ultrawides.
Vignetting is heavy f/1.8 and gets better at the other settings, as expected. "Heavy" here is still better than many ultrawide-zooms. Look at the samples above. This, to some degree, is a purely physical problem with a fullframe-sensor. Wide open, it might be around 2.5 stops darker in the corners, with a quite strong and hard drop off within the last few millimeters of the frame, and gets better with stopping down. Positive is, that most of the frame is quite evenly lit, so that this is not visible on APS-C.
The aperture is made of 9 blades, giving you very smooth out-of-focus highlights extraordinary 18-ray-light-stars.
I have no information on this lens' usability for for infrared-photography, sorry.
While I think, that a lens less prone to flare and especially ghosting is not always better, as at least ghosts can be a very nice tool to show the lighting conditions in your pictures, this 20mm isn't overly prone to flare, but has quite a big and bulbed front-element, so has a higher possibility of catching light-reflexes, than other lenses have. Well, even when it flares, you do only get some greenish or redish ghosts, but Sigmas 12-24 or 15-30 are worlds worse and the picture doesn't "glow out", making it unusable due to loosing contrast. Gladly, lamps, the moon, candles or similar light-sources in the dark aren't a problem and you can always avoid it by changing the angle a bit.
It's color reproduction seems to match my other Canon EF and third-party lenses. It does not have the little bit warmer overall cast, old Sigmas sometimes show.
Lateral CAs (purple/green fringes along high-contrast edges) are very well controlled for such a lens, thus still visible and can reach a width of above a bit below one pixel, I'd estimate.
Sharpness is one of the most overrated qualities of lenses. That being said, this lens, this sample, other than the ones tested at photozone or that I have rented in the past, is sharp even at f/1.8 in the far corners on fullframe. Unbelievable but true. This is a 100% crop from the extreme top-right corner of a 22MP JPG from my 5D Mark II:
... well, this is simply extraordinary. I couldn't believe it at first, but looking at the EXIF, it really is f/1.8 and it really is fullframe. WOW.
And no: The other corners are about the same, it's even centered well.
If it'd take 77mm filters, it'd be my only fullframe ultrawide now.
Alternatives
None. This lens is unique. Of course there are several ultrawide options, but no other "macro ultrawide" so fast.
I have always refused to want this lens because of the really bad reviews, but honestly: After using it a bit I can really say, that you HAVE to own one! Even if you get a crappy sample, it doesn't matter, because the view it creates is so cool and so unique, that you really want one... as long as you like ultrawide and close-up shooting, of course, otherwise you won't know what to do with it ;-)
Strongly recommended!
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