Is This Sigma's Sharpest Ever Lens? A Review of the 40mm Sigma Art

"This is probably the best Art lens they've ever made." That's what Kai Wong said after testing the Sigma Art 40mm. Read on to see why.

In this review, Kai Wong takes to the streets of London, and in his dry, laconic style, shoots a bunch of merry and perhaps inebriated Santas. The first thing you notice and the first thing Kai talks about is the gigantic size of the lens. He describes it as fat, long, and heavy, and shown in his hands, it is an absolute whopper on the end of his Sony a7 III. Granted, he's using a Sony adapter as the lens has a Canon mount, but still, it's almighty big. He says it feels front heavy and is quick to point out it's one thing he doesn't like about the lens.

For many, a 40mm lens is an odd focal length for street photography, but as Kai rather humorously says, it's not too wide like a 35mm and it's not too narrow like a 50mm. I have to agree with that, as I often find myself taking my little pancake Canon 40mm around with me when I'm shooting my daughter downtown here in Japan. It seems to fit snuggly between the wide(ish) 35mm and the 50mm, which I often find doesn't get enough of the frame I want.

He says the details are as sharp as a knife edge and crisper than reality, especially when opened up on a big screen. Its bokeh is outstanding, which is always high on the checklist if a lens wants Kai's approval. After he's done shooting Santas and being pelted with brussel sprouts, he goes back to the studio and compares the Sigma Art 40mm with a Canon 50mm f/1.2L and a Canon 35mm f/1.4L II. Against the 35mm lens, the Sigma is sharper, has more pop throughout, and doesn't soften towards the corners like the 35mm does. And against the Canon 50mm f/1.2L, the difference is astounding when both are shot wide open. The Canon looks horribly soft in comparison and doesn't even get close when stopped down. 

One thing I do have to strongly disagree with is his indifference to Sigma's USB lens calibration dock (sold separately). In his review of the Sigma 50mm Art lens he made similar remarks about the lens calibration dock, which I chuckled along with at the time. However, when I went out and bought the 50mm Art lens, I wasn't chuckling in the slightest after I found that the AF was quite hit and miss at different distances, sometimes quite significantly. Against my better judgment and despite my cynicism, I went out and bought the USB dock and went through the time-consuming process of calibrating my lens. The dock works perfectly. Why the lens settings were considerably off coming out of the factory is anyone's guess, but it seems a consistent problem with the Art lens series. Be that as it may, the USB dock and the calibration options really do work, and I have gone from about a 60 percent keeper rate with the 50mm to about a 95 percent keeper rate without doing anything differently. Thus, you may chuckle along with Kai but the calibration dock really does work.

Priced at around $1,400, the 40mm Art lens seems an absolute bargain, especially when Kai says he thinks it would even give the Zeiss 55mm f/1.4 Otus Distagon a run for its money (at $2,600 cheaper, thank you very much). How do you feel about this Sigma 40mm lens? Are you tempted by it despite its massive size? And what have your experiences been with other Sigma Art lenses? I'd love to hear your thoughts in the comments below.

Iain Stanley's picture

Iain Stanley is an Associate Professor teaching photography and composition in Japan. Fstoppers is where he writes about photography, but he's also a 5x Top Writer on Medium, where he writes about his expat (mis)adventures in Japan and other things not related to photography. To view his writing, click the link above.

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Just speculation, but maybe the reason the auto focus wasn't as it should be out of the box is due to the fact you were using an adapter and a Sony vs. the Canon it fits natively? I've noticed that same thing before using adaptive lenses on a different system.

Or were you using it on a native mount?

No I was using it on a native mount. Canon for Canon. It seems to be a rather common issue. No idea why to be honest but the dock and the calibration process fixed it all. Thankfully the dock is only $60 but it’s still $60 I would have preferred not spending...

But DSLRs will always have that issue. Because the lenses probably worked well in their test unit from the factory but still won't guarantee that it will be the same for your camera. This is the very reason why lens calibration exists for end users.

Yes I don’t doubt that at all and you can’t expect every lens to be perfect out the box. However, a quick glance around the net and you’ll see that Sigma Art lenses, much more than many others, seem to have calibration issues out the box.

I had terrible hit/miss issues with the 50mm Art when I first got it. Also seemed like it would be more on if using focus sides on one half of the sensor vs. the other. Sent it in to Sigma and it came back the way it should have always been. Maybe they calibrated something better. But it saved me from having to buy the dock... ;-)

Funny that I live in Japan and never even thought of sending it to Sigma haha. I like to be the master of my own successes. And horrible failures...

Bought this lens yesterday. Both copies available in the shop had front focus issue, but since I already own the USB dock, I decided to buy it anyway. After an hour of calibration, it seems that the lens is -14 at MFD, -20 at mid ranges, and -8 at infinity, so in body af fine tune would be useless. However once calibrated the lens is magnificent, and definitely worth the effort.

At the same time, last time when I bought a Sigma 135mm, despite having much narrower depth of field, the focus is spot on without any adjustments. It really is a toss up.

It really is a puzzle why these Art lenses are often so horribly off coming out of the factory. I wonder of the calibration guys at Sigma have had one too many sherbets before they do the calibrating.....Glad to hear you got yours sorted though. They are wonderful lenses when the calibration is worked out.

I think the dock is a low cost option to have all your Sigma ART lenses working at their best. Instead of paying more for Sigma to take the time to calibrate every lens and then dealing with occasional returns due to calibration issues, you buy the lens at a lower initial cost. You then buy one dock and it services all your Sigma lenses. It also allows firmware updates as well as customizing features related to the AF and zoom.
It the long run it will save Sigma owners money

Couldn’t agree more. The sad old cynic in me thinks that the calibration issues might be a deliberate ploy by Sigma to squeeze an extra $60 out of consumers, considering the docks are sold separately. I’d love to believe not, but there seriously must be some reason or explanation as to why these ART lenses are so consistently off coming out the factory.....

I still don't get why a 40mm? They have a fantastic 35mm f1.4 Art already. This lens is super super sharp and it's only $899 ($799 sale as of this post).

You make a good point. Cheaper, smaller, lighter and only 5mm different, it seems a no-brainer to get the 35mm. Still, the results are fantastic and as I said, I sometimes notice a bit of wide angle distortion with my 16-35mm shot at 35mm whereas I don’t get it with my little pancake 40mm.....

Guess he hasn’t shot with the 105mm 1.4

That’s the best lens I’ve ever used, hands down.

Have you shot with this 40mm lens?

Which maker?


I know these comments are from 2018 and this is October 2020. People still read the comments I believe.
I had the Sigma art 50 and struggled with it even after calibrating every 6-8 months. I sent it into Sigma and they went through it . It was better right off then B&H put the 40mil art on sale for $999 . I’d always disliked the 50mm fov. It just was slightly too tight I thought. So I called a buddy and asked him if he wanted my 50 . He did , so I immediately bought the 40 art . I love the lens , it was very close straight out of the box . With some calibration it is awesome. Like the 50 you have to give it time to focus . It is not a speed demon at all . Also like the 50 it has focus shift when changing apertures . From f/1.4 to f/5.6 it’ll change . If I remember correctly it’s a front focus. I haven’t shot it for a couple months . I think I calibrated mine at f/2.0 for a split then changed it to f/1.4 calibration can’t remember now .
All and all the forty mil is a great documentary style lens . On the street it to me can feel tight . But get at events and it comes alive. I think if my gimbal could handle it (bad motor) I’d use it on stage for live music. I usually use 28mm but I’m thinking 40 might be nice . I also just got the Sigma art 28mm and think I now have a favorite ever lens . Before that was that Sigma art 18-35 . But the 28 art is very special.