MTF Tests for the Sigma 14-24mm f2.8 Art Series Lens

Most of you know I’m a big fan of Sigma’s Art prime lenses. They give superior optics at excellent prices just about every damn time. I’ve been more mixed in my opinions of Sigma’s Art zoom lenses. I thought the Sigma 24-105mm f/4 Art was the best 24-105mm I’ve ever tested (and I hate testing 24-105s). The Sigma 24-70mm f/2.8 Art, on the other hand, I thought was adequate.

Sigma 14-24mm Art Series

I wasn’t sure what to expect from the Sigma 14-24mm f/2.8 DG HSM Art, so I was eager to test it and grabbed copies as soon as we had them in stock. Why then, you may logically ask, am I just now writing it up? Well, partly because I have jobs that like, you know, pay me to do stuff. And somewhat because this became an exciting learning experience that I’ll tell you about at the end of the post.

About the Lens

Years ago, Nikon came out with their Nikon 14-24mm f2.8G ED lens. It was a revolution; wider and sharper than any other wide zoom made at the time. It remained the gold standard of wide zooms for years. Sigma isn’t filling a void here; Nikon already has an excellent 14-24mm, and Tamron has the not-quite-as-wide but really close 15-30mm f/2.8 Di VC USD.

The Sigma is less expensive than the Nikon by $400, but $200 more expensive than the Tamron 15-30mm f/2.8 Di VC USD. The Sigma, at 1150 grams is a bit heavier than the Nikon (1000g) and about the same as the Tamron (1100 gm).

So I thought that the new Sigma should be as good as the Nikon 14-24mm and better than the Tamron 15-30. That’s a tough task. Yes, I’m aware someone is going to make noise about other lenses. First, f/4 is not f/2.8. Second, 16mm is not 14mm, they are very different beasts (not to mention, most 16-35mm zooms are actually 17mm at the wide end).

One Disclaimer

Of course, the usual ‘this is not a lens review, it’s an optical test’ stuff applies to this post. One other thing needs to be mentioned when we test full-frame f/2.8 lenses wider than 16mm; we are either right at, or possibly past, the limits of our machine. It’s complex, it’s arguable, but it deserves mention that you should probably consider the graphs in this post ‘close, but might not be exact’ at the outer edges.

Also, I’ve violated my usual testing protocol for the first time, and I think you should know that. The test I’m showing you today is my second set of 10 copies of the lens, not the first 10. If you’re interested in why you can read about it in the addendum.

Optical Testing

As is our practice with 2x zooms, these lenses were tested at both ends (we do middle focal length testing on 3x and longer zooms). To start with, let’s mention the actual focal length of the lens is 14.3mm to 23mm. I mention this because that’s less ‘fudging’ than the label usually has; +/-5% is pretty standard for a zoom. Distortion is also reasonable: 0.8% at 14mm and 1.1% at 24mm. At both ends the distortion is mildly mustache shaped – a bit like the Zeiss 21mm f/2.8.

MTF of the Sigma 14-24mm f/2.8 DG HSM Art

At 14mm

This is an excellent resolution. About halfway to the edge, we start to see some astigmatism-like separation of the sagittal and tangential lines (it could also be the lateral chromatic aberration).

As I mentioned above, 14mm full-frame lenses are right at the limits of our machines automation. The drop in tangential MTF you probably note at 4mm away from the axis is perhaps a testing artifact; I won’t bore you with details about distortion being mapped at insufficient points for a very wide-angle lens. It could also be caused by an aspheric element. I can’t say for sure. 

Olaf Optical Testing, 2018

At 24mm

The resolution is even better at 24mm, just excellent across the field, and with no testing artifacts.

Olaf Optical Testing, 2018

Stop-Down MTF

The above graphs are the average of all ten copies tested at the widest aperture. We took one typical copy and stopped it down for retesting. There is a marked increase in resolution at f/4 compared to f/2.8. There was very little change between f/4 and f5.6 so I’m not going to clog things up with those graphs.


Olaf Optical Testing, 2018



You may notice that the MTF graph looks a little worse at the edges at f/4. This is a complicated thing that involves distortion, the lens’ field curvature, and a change in focus point of the machine, not a real thing.


Olaf Optical Testing, 2018

MTF Comparisons

Nikon 14-24mm f/2.8G ED

We’ll start with the comparison to the long-term gold standard, the Nikon 14-24 f/2.8G ED. The Nikon is a much older design, of course, but still a superb lens.

At 14mm

Here is an excellent example of two great lenses that are different, not one-is-better. Both are excellent in the center. In the outer 1/3, the Nikon has less sagittal-tangential separation; the Sigma has higher resolution. Will that make a difference in your image? With careful comparison, you might notice the Sigma has better corner resolution, but perhaps busier bokeh. You might not notice any difference at all.

Olaf Optical Testing, 2018

At 24mm

At 24mm the Sigma is strutting its stuff. It’s sharper everywhere. This difference should be noticeable, for sure.

Olaf Optical Testing, 2018

Tamron 15-30mm f/2.8 Vi DC USD

At 14 vs. 15mm

The Tamron is an excellent lens at the wide end, very comparable to the Nikon. As with the Sigma-Nikon comparison, I won’t try to call better (especially given that we’re testing at the limits of our bench). The Sigma may be a bit better in the center; the Tamron maybe a bit better at the edges. Again, though, we’re straining the limits of our testing capabilities here, so I can’t say there’s any noticeable difference.

Olaf Optical Testing, 2018

AT 24mm vs. 30mm 

Again, it’s not close at the longer end; the Sigma is clearly better here.

Olaf Optical Testing, 2018

If you want a really good example of just how hard it is to do 14mm, here’s a comparison of the Sigma 14-24mm f/2.8 with the Canon 14mm f/2.8 prime. Depending on what you emphasize, the Sigma comes close to violating Roger’s Prime Directive: No zoom is as good as a prime. In this case, the zoom may be better.

Olaf Optical Testing, 2018

The Canon is not the best 14mm prime; I chose it because f/2.8 to f/2.8 makes a nice comparison. The Sigma 14mm f1.8 Art is the best 14mm prime. At f2.8 is better than any of the others. So Roger’s Prime Directive holds true.

Olaf Optical Testing, 2018.

 Field Curvature

Let’s leave the fanboys behind to argue about the comparison MTFs and get into something useful for photographers who actually use the lens; the field curvature.


The sagittal field is a gentle M curve (lower left) while the tangential field (lower right) is a strong W. This gives the overall field (upper left) a bit of a U shape, and more importantly, means there’s going to be some astigmatism at the edges. It’s a 14mm lens, after all.

Olaf Optical Testing, 2018

The strong field curvature affects the standard MTF curve (it is focused in the center, so the edge MTF is low partly because it’s out of focus). We can pull the data above to give Best Individual Point MTF (BIF). This is a theoretic measurement, showing how much resolution you can get if you focus on that specific point rather than the center.

Below is the center focus MTF on the left, the BIF MTF on the right. As you can see, if you focus off axis, you can get near-center sharpness just past halfway to the edge. Beyond that, you can get good sharpness, but you will have some astigmatism.

Olaf Optical Testing, 2018

As I mentioned above, if you focus off axis, the center of the image will get softer, because of field curvature. Since 14mm is used for landscapes at times, it can be useful to find the best focus point – the place that if you focus there, you get the best overall sharpness from corner-to-corner. Below is a graph showing where we calculate that point should be, and what the MTF would look like if you focused there.

Olaf Optical Testing, 2016

So, if you want to get the best edge-to-edge sharpness on your landscape shot, focus a bit less than halfway to the edge of the image; that will give you the best average sharpness across the frame.


At 24mm the tangential field is still slightly W shaped, while the sagittal is a shallow U shape. The important thing is they are more similar to each other, and the overall field is a gentle U with less astigmatism than at 14mm. This is a really nice performance for any lens (even a prime) at 24mm.

Olaf Optical Testing, 2018

When we compare the center focus MTF (below left) with the Best Individually Focused MTF (below right) we see that at 24mm you can get excellent sharpness throughout most of the field; even at the edges, things are very good.

Olaf Optical Testing, 2018

If we find the focusing point that gives our best overall focus, once again it’s at 8mm from the center, just about halfway to the edge of the image. That’s convenient; the Best Average Focus point is at the same place at either end of the zoom. Less to remember.

Olaf Optical Testing, 2016


I said at the beginning that I expected this lens to be at least as good as the Nikon 14-24mm f/2.8 and better than the Tamron 15-30mm f/2.8. I think it’s pretty apparent that while they are all within hair splitting distance of each other at 14mm, the Sigma is the best at 24mm. Optically, this one is worth the money and the best overall 14-24mm zoom. There are lots of other things that go into choosing a lens, but at these very wide angles, things like autofocus speed are not big points.

That being said, if you’re buying a 14mm lens to be a 14mm prime (and some of you are), then all three of these do very well. Honestly, though, for a little more money you should consider the Sigma 14mm f/1.8 Art if that’s the case. If you’re thinking of matching a 14-24mm f/2.8 with a 24-70mm f/2.8 to collect the whole focal length set, then the Sigma is the best optical choice.

Two things I’ll mention. First, for the 72,534 of you that want to compare it to 16-35s, go right ahead. But it’s not a fair comparison, and I’m not going to do it. 14mm is very different than 16-35; much more difficult to design and manufacture. If a 16-35mm will meet your needs, and hold your filters without additional contraptions, then get a 16-35mm.

Roger Cicala and Aaron Closz

July, 2018

Addendum: Sigma’s Response

Our protocol is always the same: the intake people inspect and test lenses on test charts, fail anything that’s obviously bad and pass the rest on for testing. I test the first ten lenses they send me to write the blog post.

This time a weird thing happened. On testing day 1, I tested the first eight copies of the Sigma. At 24mm five of them were identical and excellent. Three were not OK and was a big gap between the two groups. This is NOT normal. Generally, we see a cluster of lenses that are good, a lens that’s not quite that good, another not quite as good as that second lens, etc. In other words, the variance is always a steady trend away from best.

This is not something I’ve ever seen before in testing hundreds of lenses. I have a good working relationship with Sigma, so I emailed them as a courtesy, as I do with any manufacturer that corresponds with me. (They generally ask me to retest and want to argue about why my results aren’t valid. I generally retest and find my results are valid.)

Sigma didn’t do this. Instead, they asked for the serial numbers of the lenses. A few hours later they told me they had pulled the tests of those lenses at the end of the assembly, that the three lenses in question had tested much better than this at the factory, and asked me to send them to Japan for repeat testing.

Most of you don’t realize the enormous shock this caused me. I’ve been testing lenses for a decade and working with manufacturers for nearly that long. Leica has this kind of testing for every lens. Zeiss has it for certain lenses in their lineup. Nobody else does. Leica lenses. Some Zeiss lenses. Sigma Art lenses. Yes, I know all about other claims of ‘we test every lens’; that means it was mounted to a camera to program the AF firmware. Nobody else (with the possible exception of Canon with some of their newest lenses, and I’m not certain of that) is testing every copy optically and keeping the results on file.

Ten days later (shipping to Japan takes a while), Sigma emailed to tell me the lenses I sent back tested much worse than their original end-of assembly tests. Their new tests agreed with my findings and were, in their words ‘not acceptable for this lens.’ I’ve heard ‘this lens is within spec’ from manufacturers on lenses I knew were bad so often, for so long, that I reread the email just to be sure. To paraphrase a bit: “We have retested the lenses and agree with your findings. They aren’t good now. They were quite good when they left here. We’re investigating to find out what happened.”

Then they had their engineers disassemble the lenses and found some minor damage to rollers consistent with an impact that had caused the problem. I’ll be blunt, usually, I’d expect a ‘so you guys must have dropped them’ next, because these came from 3 different suppliers. And that is certainly possible. The lenses passed through several hands here on their way to me, and while very rare, things get dropped (and that people dropping don’t always admit they’ve dropped).

Instead, Sigma said they would track the shipment and see if the lenses were in the same crate or pallet during transit. Then they told me something that made me nearly weep with gratitude, showing that in a few companies engineering, not marketing, still runs the show:

Our engineers have also taken a number of new lenses from the assembly line, dropped them in various ways, and then disassembling them to look for damage. We did this until we had reproduced this type of damage. We will now see if there are changes we can make in the lenses or packaging to prevent this from happening in the future.

This is, in my opinion, what superb engineering and quality assurance are all about; look for any weaknesses and strengthen them. I’ve been working in this industry for many years, and this is the attitude I wish every company had, but few do.

Also, to be as certain as I can that the tests I’ve presented here are representative, I’ve tested a total of 25 copies now; the three damaged lenses were the only ones with any issues.


OFFTOPIC – And a bit of fun, for both of you that read this far.

I LOVE where you have to write using only the 1,000 words most commonly used in American English. So, I rewrote a couple of paragraphs until they passed the test. If you want to try your hand at it, the two original paragraphs are under “14mm field curvature”. Post your results and shame me with how poorly I did.

The way the field moves changes how close to perfect the MTF (which is focused in the middle) is. We can pull the numbers above to give Best-at-each-point MTF. This is not a real world thing, because if you focus on that point, rather than the middle, the middle gets soft.

Here is the middle focus MTF on the left, and the Best-at-each-point MTF on the right. As you can see, if you focus away from the middle, you can get as good as you would see in the middle, until you go past half of the way to the edge. If you go further you can get good pictures, but the lines going away from the middle won’t be the same as the lines going across those lines going away from the middle.

Author: Roger Cicala

I’m Roger and I am the founder of Hailed as one of the optic nerds here, I enjoy shooting collimated light through 30X microscope objectives in my spare time. When I do take real pictures I like using something different: a Medium format, or Pentax K1, or a Sony RX1R.

Posted in Equipment
  • 1.) Could it be possible that these field curvature measurements are /significantly/ different at infinity, where field curvature matters a whole lot for nightscape photographers?

    2.) It is pretty clear that the Sigma 14 1.8 Art is just bonkers, compared to any of the zooms that get to 14/15mm. However, do you have any results for the new Rokinon 14 2.4 SP / Samyang 14 2.4 XP, …or have you completely given up on having these brands in your arsenal at LR? [EDIT: scratch that. I do see that the 14 2.4 is in your arsenal. Have I missed its review being posted on this blog, or has it just not been put on OLAF?]

    3.) “Our engineers have also taken a number of new lenses from the assembly line, dropped them in various ways, and then disassembling them to look for damage. We did this until we had reproduced this type of damage. We will now see if there are changes we can make in the lenses or packaging to prevent this from happening in the future.”

    …MY DREAM JOB EXISTS. (I need to learn Japanese and get a few engineering degrees, though…)

  • Bakari Taylor

    That was really cool to hear about Sigma’s response. Before the Art series of lenses no one was really taking Sigma seriously, they were a great inexpensive, so so option. Today they are are one of the best lens manufactures period. It really is quite amazing.

  • ipdouglas

    Very interesting real-world article! Totally agree with the Quality Assurance activities. Might have expected the Sigma engineers to have conducted ‘drop tests’ first rather than later but perhaps the damage was from some unusual impact different from a norm? Looks like a new QA test here?
    The comments and results do not exactly correlate with the group wide-angle zoom test where the Nikon 14-24mm was preferred rather than equivalent? However as usual I absolutely love you tests and the blog so thanks Roger!

  • kimH

    Again an excellent story for all us out there “geeking”. Adding the SIGMA story is the coolest, you have officially become an authority @LR – but WE who follow you with joy, all knew that already. Thanks for the work, please don’t stop!

  • kimH

    Excellent 🙂 – actually it struck me that I often focus landscapes about half-way to the corner(s) of the image. Now i know why 🙂 🙂

  • Jeremy Van Pelt

    Not sure about that. I would feel pain each time I did that to a beautiful lens, even though it was for a good cause.

  • obican

    Are you kidding, even the word “thousand” is not among the top 1000 words 😛

  • obican

    Thank you, Roger.

  • Max Manzan

    Thank you Roger for this blog post, I found the addendum very interesting.
    I’ve been admiring Sigma as a company since they introduced their Global Vision concept and particularly their Art lens line. Now I’m admiring them even more.

  • Dragon

    One note re the Tamron. Your earlier testing of Tamron showed that it was very good at 24m (actually 23mm because your were comparing it to the Nikon at the time and didn’t want to push the Nikon the stop). At 23mm it is not quite as sharp as the Sigma in the center, but probably the best of all across the field. I have one and have found it to extremely sharp at 24mm on a 5DSR. The only downside I know of is that it came out before the Tap-in console and you have to send it in for firmware updates. My favorite Sigma is the 150mm macro. It eats razors for breakfast.

  • Messier77

    Roger, thanks for the wonderfully in-depth test/post. Any chance you could post the BIF MTF for the Sony 16-35GM? Thanks!

  • It’s a very deep thought, that quality is not among the 1,000 most common words.

    I think your translation is much clearer than mine.

  • I can say I don’t know anyone in their marketing department (and all marketing departments despise me; of which I am most proud). I directly contacted and spoke with only engineers (we have had technical discussions about testing for years and I have met a number of them) and their response was immediate. The discussion was entirely about test results, testing, etc., I sent them all of my results and they sent me theirs.

  • Franz Graphstill

    That’s wonderful news about Sigma’s idea of quality control.

    I’ve been getting thoroughly sick of the claims from various people that Sigma Art lenses can’t focus reliably, and that Sigma has no idea of quality control. This is going to be my favourite counter-example from now on.

    I’m not interested in wide-angle lenses – nothing wider than than 50mm, in fact. The Sigma Art 85mm and 135mm, though, are rapidly becoming my favourite lenses. Yeah, they are big, but I don’t care – I look at the image quality that I get, and laugh at the people who complain about the weight (well, they have to complain about something, and that’s about all they have!).

  • Samuel H

    That Sigma story in the adendum is just mindblowing. It shouldn’t, but it is. I’m truly amazed.

  • Franck Mée

    Okay, here’s my take on the “only common words” challenge. I’d say, as a French, I thought it’d be easy for me (I don’t know that many words to start with), but it was actually rather difficult — what, “quality” isn’t even in your top 1000 words?!

    The way the field is not straight changes the lines about how good the picture is (it is focused in the middle, so the how-good-lines are lower on the edge because it is out of focus). We can work the numbers above to give Best Number for Each Point. This is not a real thing, it just shows how good you can get if you focus on that point rather than the middle.
    Here is the how-good-lines focused on the middle on the left, the Best Number for Each Point on the right. As you can see, if you focus off on the side, the area where you can get almost as good as in the middle is a bit wider than half the picture. Further, you can get a good picture, but lines will look different if they’re one way or another.

  • David Bateman

    Dropping lenses off the line to reproduce damage sounds like the best job ever.

  • Ben

    The cynic in me says their marketing department knows exactly how much of an influencer you are and told you exactly what was needed to ilicit r addendum. I have zero reason to believe this is true, but it’s worth asking if they sent you their tests results. I had the 35mm Art when I was Canon user and now use the 135mm 1.8 adapted on the GFX. Both are fantastic lenses, so I’m not surprised by their QA. They have always claimed to use their Foveon sensor to test every lens.

  • Very true on the stabilization, Brandon. I won’t believe in weather sealing as long as the warranty doesn’t cover water damage, but I’ll go with ‘more resistant’ and that, too, is a pertinent point.

  • Brandon Klemets

    Worth noting the Tamron is the only option if you need pro weather sealing or image stabilization

  • Tom Hoyle

    I’ll probably never own this lens, but Roger your blog post is still well worth reading. Thanks for always being entertaining and informative.

  • Athanasius Kirchner

    That rewritten paragraph is terrible, but I highly doubt I could do better.
    Please keep on using your technical language – if that doesn’t scare the artsy types away, the focus field graphs and conspicuous absence of cat photos will 😀

  • Athanasius Kirchner

    Oh, I can already see the forum headlines:
    -How many people have a broken Sigma 14-24mm? (Poll)
    -I fear my new UWA zoom might be damaged – is yours too?

    It’s too late now. The paranoia spreads like wildfire :/

  • OMG – Now I know why I love Sigma Art lenses. I’m just hoping that the new E-mount lenses addresses the focus performance problem.

  • Thanks for sharing that graph Roger! That does look markedly different from the graphs above, but as your techs also thought, not completely out of line for a wide zoom.

  • Clayton Taylor

    Roger, this might be your most significant blog post yet – not one but TWO bombshells! The fact that the Sigma zoom almost violated Roger’s Prime Directive is significant. The story in the Addendum about Sigma’s reactions to your tests left me amazed. My level of appreciation and respect for Sigma as a company has risen dramatically. I am totally in love with my new a7III, and now there might be an Art Lens in its future.

    I am guessing that someone at Canon, when reading your post, uttered the Japanese equivalent of “Oh, crap!” – not once but twice.

    Last thing – does this mean that, like a Marvel action movie, we now have to read right to the very end of all your future posts in order to find Cicala Easter Eggs?

  • If you had two side-by-side you’d see it, there was an overall reduction in resolution and there was some side-to-side variation. If you compare this full graph to the average 24mm MTF above, you’ll see the difference easily.

    The question is more why didn’t the screening techs see it. Their answer was they were all great at 14, and being the first batch the techs didn’t know what to expect. They were thinking ‘like the Tamron 15-30, which is great at 15 but weaker and with variation at 30mm. This was compounded because the lenses came in batches of 3 or 4 from different suppliers, so nobody on that first day got to look at all the lenses except me.

  • Thanks for the test and the cool Sigma story, but now I can sense the lens hypochondriacs lining up …

    Speaking of which, what did the damaged lens results look like? Was it just lower overall resolution all around, or was there some kind of obvious asymmetry in the test results? I’m wondering if a normal person without an optical bench could have seen this with some kind of asymmetry test at home.

  • William Dyer

    Thank you for this extensive test report. I appreciate all the time and effort you put in, and your reviews do have an impact on the lenses I choose to purchase. While I think I’ll stick with my Tamron 15-30, having invested in a filter holder and 150mm filters, it is interesting to see it against the Nikon and Sigma. And as the owner of these Sigma lenses: 35 Art, 50 Art, 24-105 Art, 135 Art, 150 macro and the Sig-monster 300-800, it’s heartening to know Sigma’s engineers are serious about quality lenses. I remember many years ago, Sigma made a 24mm 2.8 with built in skylight, yellow, blue and orange filters. Very convenient, but the image quality was awful. Those days are gone.

  • Carleton Foxx

    “Then they told me something that made me nearly weep with gratitude…” now you know how your readers feel every time you post one of these articles.
    So, please keep taking your Lipitor and remember that you don’t have to eat the whole rack of ribs when you go out for barbecue.

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