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Lenses and Optics

MTF Tests of the Sigma 35mm f/1.2 DG Art

We just finished testing a couple of 35mm prime lenses and came away quite impressed. But it took a little longer to finish testing the one everyone had been asking about; the Sigma 35mm f/1.2 DG Art lens. I declared the Tamron 35mm f/1.4 SP the sharpest 35mm lens we had tested just a week ago, so we were all curious if that title would hold up after the Sigma was tested.

So curious, in fact, that I broke the MTF Testing Rule I Always Refuse to Break. I actually tested the Sigma at both f/1.2 AND at f/1.4. Why did I finally break the rule? Cause I wanted to. Will I break it again, if you ask nicely, have a really good reason, and are on a Holy Quest? Nope.

Let’s take a second to do a quick comparison of the Sigma f1.2 with other 35mm wide-aperture prime lenses (including some for other mounts, because a lot of people are shooting other mount lenses on Sony cameras).

LensPriceWeight (g)Length (mm)
Sigma 35mm f1.2 Art$1,4991090136
Tamron 35mm f1.4 SP$899
815105
Sony FE 35mm f1.8$74828173
Canon 35mm f1.4L II$1,699760105
Sigma 35mm f1.4 Art$69966594

Obviously, if the widest aperture isn’t that important, the Sony FE 35mm f1.8 provides a much smaller lens with great image quality at a cheaper price. A lot of you may not realize the Sigma 35mm f1.4 Art is the least expensive option, yet still provides superb resolution. The Tamron 35mm f1.4 SP was recently declared (by me) to be the resolution champion at this focal length and is an awesome bargain at its price.

The Sigma 35mm f/1.2, though, gives you f/1.2, and some of us, at least, lust after f/1.2. You pay a price for f/1.2, both in dollars and in lens size. The question really is, as we say in the South, so what all comes with that? Because we all know a lot of f/1.2 lenses are ‘wide-aperture, hold the sharpness’.

A Quick How to on Reading MTF Charts

If you’re new here, you’ll see we have a scientific methodology to our approach, and use MTF charts to measure lens resolution and sharpness. All of our MTF charts test ten of the same lenses, and then we average out the results. MTF (or (or Modulation Transfer Function) Charts measure the optical potential of a lens by plotting the contrast and resolution of the lens from the center to the outer corners of the frame. An MTF chart has two axis, the y-axis (vertical) and the x-axis (horizontal).

The y-axis (vertical) measures how accurately the lens reproduces the object (sharpness), where 1.0 would be the theoretical “perfect lens.” The x-axis (horizontal) measures the distance from the center of a lens to the edges (measured in millimeters where 0mm represents the center, and 20mm represents the corner point). Generally, a lens has the greatest theoretical sharpness in the center, with the sharpness being reduced in the corners.

Tangential & Sagittal Lines

The graph then plots two sets of five different ranges. These sets are broken down into Tangential lines (solid lines on our graphs) and Sagittal (dotted lines on our graphs). Sagittal lines are a pattern where the lines are oriented parallel to a line through the center of the image. Tangential (or Meridonial)  lines are tested where the lines are aligned perpendicular to a line through the center of the image.

From there, the Sagittal and Tangential tests are done in 5 sets, started at 10 lines per millimeter (lp/mm), all the way up to 50 lines per millimeter (lp/mm). To put this in layman’s terms, the higher lp/mm measure how well the lens resolves fine detail. So, higher MTF is better than lower, and less separation of the sagittal and tangential lines are better than a lot of separation. Please keep in mind this is a simple introduction to MTF charts, for a more scientific explanation, feel free to read this article.

MTF Results

For an f/1.2 lens, the MTF chart is really, really good. Center resolution is excellent. Away from center resolution is well maintained, although, there is some sagittal and tangential separation, which indicates either a bit of astigmatism or lateral color. This is expected in very wide-aperture lenses, though, and it isn’t severe.

Lensrentals.com, 2019

 

Since we’re all used to looking at f/1.4 MTF charts, it’s worth pulling up some other f/1.2 comparisons to show just how sharp this is for an f/1.2 lens. The only other 35mm f1.2 I have data for is the Voigtlander Nokton 35mm f1.2 Mk II. The Voigtlander is an older, smaller, less expensive, manual focus lens so we didn’t expect it to keep up with the Sigma; and it doesn’t.

 

Lensrentals.com, 2019

 

The classic old Canon 50mm f/1.2L is an f/1.2 lens and while it’s obviously not a 35mm focal length, it’s still worth a comparison. It was never considered a sharp lens, even back in the old days, though. (And before you ask, no I can’t test the RF 50mm f/1.2 yet, so I don’t have that logical comparison available.)

Lensrentals.com, 2019

 

The sharpest ultra-wide aperture lens that I had tested (before now) at f/1.2 was the Leica Noctilux-M 75mm f/1.25 ASPH. Despite the Leica’s $12,000 price tag, the Sigma is indeed sharper. I was honestly a little surprised at this.

 

Lensrentals.com, 2019

So I think we’ve settled the question as to whether the Sigma is the sharpest f/1.2 that we’ve tested. (From computer-generated MTF charts I do think the Canon RF 50mm f/1.2 will test sharper, but, as I said, I can’t test it yet.)

I Know What You’re Thinking

So, it’s a really amazing sharp lens at f/1.2. Those of you who really need f/1.2 are already off ordering it somewhere. But a lot of people are thinking, well, I’d like me some f/1.2, but I really want to know how it compares to the 35mm f/1.4 lenses. I know it should sharpen up a bit at f/1.4, but how much? So, for this one and only test, because 1) I wanted to know, too; and 2) I had a rare day where the optical bench and I both had nothing else to do; I ran 5 of the Sigma 35mm f/1.2 lenses at f/1.4.

 

Lensrentals.com, 2019

 

Just slightly stopped down to f/1.4 we have a significant improvement in resolution in the center of the image, but not much change in the outer half. (For those of you who think ‘stopping down improves things everywhere’; no it doesn’t. It’s specific to each lens and depends on which aberrations the lens has. Some lenses sharpen up all over, some in the corners first, some in the center.)

I used those f/1.4 results to do a couple of comparisons to other 35mm f1.4 lenses. We’ll compare it first to the Sigma 35mm f/1.4 Art, which is an excellent 35mm.

 

Lensrentals.com, 2018

 

The Sigma 35mm f1.2 DG Art is clearly a bit better than the original f/1.4 Art. It is a newer, larger, and more expensive lens. But, I honestly thought the f/1.2 lens would be less sharp than the f/1.4 before doing this test. Because historically f/1.2 lenses have been.

So now the question becomes, is it as good as the Tamron 35mm f1.4 SP, the lens that just 10 days ago I declared the sharpest 35mm we’ve ever tested?

 

Lensrentals.com, 2019

 

Well, it’s a dead heat in the center. Away from center, if I split a few hairs, the Tamron is a little sharper and it clearly has less sagittal-tangential separation. So the Tamron retains its title of sharpest lens in the Welterweight division.

This is where you ask me ‘could we see that difference in a photo’? Nah. The two lenses would render differently, perhaps have a slightly different color cast you might notice, etc. But even in a large print with a magnifying glass, you couldn’t say one is clearly sharper than the other.

Conclusion

We showed one important thing here. If you want to shoot a 35mm f/1.2 on a Sony camera, the Sigma is a superb solution. Unlike most ‘ultra-wide’ aperture primes, you don’t pay any sharpness penalty to use this lens. That is truly unusual, f/1.2 lenses are expected to be less sharp at the same aperture than f/1.4 lenses.

It’s actually a bit better than ‘as good as’. The Tamron 35mm f1.4 SP is a tiny bit of hair-splitting, pixel-peeping sharper. But the Sigma 35mm f/1.2 is only available for FE and L mount cameras, and the Tamron isn’t available in FE mount (although I’m sure some people will be shooting in with an adapter on FE cameras).

As always, I’m only testing optical resolution. But assuming the AF speed and accuracy, the bokeh, rendering, and other important aspects of the lens please you, this is the sharpest 35mm wide-aperture lens you can natively mount to your Sony camera, and it’s a wider aperture than any of the others, too.

If you don’t care about f/1.2, then the Tamron on an adapter (if you’re an adapter person) is awesome, smaller, and less expensive. The Sony FE 35mm f1.8 will probably be the most popular of this recently tested group; it’s small, native, and reasonably (but not cheaply) priced. The Sony FE 35mm f/1.4 ZA is also a lens that exists, although I can’t imagine anyone is considering buying one.

 

Roger Cicala and Aaron Closz

Lensrentals.com

September, 2019

Author: Roger Cicala

I’m Roger and I am the founder of Lensrentals.com. 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 Lenses and Optics
  • decentrist

    bigger,heavier,sharper…..at what point does this become comedy?

  • NRKStudio

    Any chance to seat the real king of MTF, the Zeiss 35/1.4 ZM?

    On a side note, the Leica 75/1.25 stopped down to f2 is sharper than the Leica 50/2 APO at f2 according to Leica’s MTF. Such is a wonder.

  • Just a quick question from a non-astro shooter… If you mount your camera to a “star tracker” (or whatever those motion mounts are called) aren’t you then able to shoot at f/8–if you want—since you can decrease your shutter speed without worrying about motion blur?

  • Don Farra

    Roger, thank you once again for an excellent analysis report. I have a question. As a Sony user will an MC-11 adapter with the Tamron lens change the test measurements significantly in your opinion? Thank you.

  • Pox

    Impressive. I hope Sigma does a 50mm 1.2 and a 85mm 1.2.

  • Andreas Werle

    Sorry for nitpicking, Roger.
    You said: “I ran 5 of the Sigma 35mm f/1.2 lenses at f/1.4.”, but the chart reads 4 samples.
    Greetings Andy

  • Photo Dad

    How was the copy variation on the Sigma 35 1.2?

  • Andrew Hansen

    Do you plan on testing the Leica 35 SL apo? Or any of the sl lenses?

  • No Mike, the truth is that Roger is in the pay of Sonikon to keep Canon down as part of an international plot by the Illuminati to prevent the world from seeing the brilliance of their lenses.

  • Samuel H

    WOW, Sigma is doing lots of AWESOME stuff lately.

    Is there any chance we’ll see the MTF tests from their APS-C lenses? (I’m very happy with my 16mm f/1.4 and 56mm f/1.4, I’d like to know how much resolution I’m missing out by not moving to full frame)

  • Oh, that 21 1.4, Ben Horne just switched to it from his Loxia 21 2.8, I heard about it but I didn’t know if it was any good in the corners for astro work. I had kind of just written off Voigtlander as one of the “it has lots of character!” lens companies that cinematographers and Instagrammers like.

    I’ll have to see if Ben can at least do some 4K timelapse of the night sky at f/1.4 on his next trip…

  • With megapixels these days, it’s always noticeable… 🙁

    Getting the best results out of any given lens when shooting the night sky is definitely the biggest challenge/frustration I’ve ever faced. No matter how sharp a lens is proven to be “on paper”, it can all fall apart if you miss focus by a fraction of a millimeter, (especially on modern AF lenses with abysmal focus throw) or if you heavily abuse your lens for a few months or a year, and something gets even slightly out of alignment. GeekyRocketGuy and I have seen many of our Brokinon lenses pass away in the prime of their youth from such a common ailment. 😛

    Even on my test images from the A7R3 and the 24 1.4 GM, I have some examples of f/1.4 perfectly nailing focus on stars through the entire image or plane of focus, …and a few images which inexplicably have a soft right edge despite being tack-sharp in the center, or even being stopped-down to f/2.8…

    And nowadays, there’s even more variables that could be the culprit. Did the IBIS lock the sensor at a slightly skewed angle when turning it off, causing a tilt-shift look to those few images? Or did I simply miss focus?

    I’ve resigned myself to starting my manual focus workflow somewhere between the rule-of-thirds points and the extreme corners, trying to nail focus there, and then checking the dead-center and the other corners. Because no matter how perfect you think you’ve nailed it in the dead center, there still seems to be some small %% difference in the depth of field (yes, even at f/1.4 and focusing on stars) between dead-center and the corners, so you just can’t be sure unless you actually check.

    I hope Tamron is working on more f/1.4 primes, whether for DSLR mounts or mirrorless mounts; they seem to be onto something good. Or maybe 35mm is just that much easier to do well than 24mm or 35mm, as we found with the Sigma 20, 24, and 35 1.4 Arts. I guess we’ll find out.

    Then, there’s the “fact” that Sony’s FE mount is the narrowest diameter of the big three, so if we really want to see something impressive, we should all wait until Nikon puts out their (alleged/leaked) 35mm f/1.2 for that gaping maw of a mount they have now…

    Oh, and if LR needs an astro-focused review of any of these lenses, I’d be happy to communicate with Zach S. or anyone about that. 😀

  • DrJon

    Oooh, Coma tests pretty please…

  • AndyNZ

    Great work Roger…. appreciated.

  • Athanasius Kirchner

    Well, the ZA 35mm f/1.4 has a market in my country (Chile). Sony is already the most affordable brand here, and the Zony has the smallest price tag among all the modern 35mm f/1.4 lenses (when and if they are available, to begin with). On rebate, the Canon EF comes a little bit under the Zony’s price… but then Sony also do discounts here, and then their offering is unbeatable.

  • Carl Eberhart

    Well done as always Roger ! Next please do a comparison of approx. 20mm lenses…I suggest the Tokina Firins (manual and auto), the Art, and the new (?) 21mm Voigtlander f/1.4. You can throw in the Nikkor and Zeiss if you like.

    In the astro groups people are always trying to find the “best”, that has the least coma (you can do a coma test besides your MTF, it won’t kill ya 🙂 ). The Sigma haters will always find fault with it but I think it may still be the best overall at 20mm.

  • I’m going to start citing this quote when I give astrophoto lectures.

  • Well, I said no difference, but astro photography will see it if anything does. “Optical bench – a testing method that is nearly as picky as astrophotography, but has the advantage of numerical results.”

    After I test, I go find some astro pictures to decide “so was that off-axis difference noticeable?”

  • We rarely stock 10 copies of them, so it’s not often I run them.

  • Both?

  • Grab the f/1.4 version then….even the native FE mount version still has the mechanical coupled focus ring.

  • Phillip Reeve

    Well their APOs aren’t exactly compact and very high performance. The only other Voigtlander which is a top performer in regards to sharpness in it’s class would be the 1.4/21. When we speak about the others performance is certainly not exactly class leading in regard to sharpness.

  • It would likely only prove that there is no free lunch when it comes to corner sharpness and the “mirrorless weight savings” myth. If you want a lens as relatively compact as most Voigts, you’re gonna get trash in the corners, no matter the flange distance or mount diameter.

  • Phillip Reeve

    More of that please! Would love to see more Voigtlander MTFs especially from their (APO) E-mount lenses

  • Andreas Werle

    Oh Roger, you did MTF of a Leica M-Mount Lens! 🙂

  • “The Sony FE 35mm f/1.4 ZA is also a lens that exits.”

    Typo or Freudian slip? 😉

  • They need a mount for it on the machine before they can test it.

  • Trey Mortensen

    Curious as to why you can’t test the 50 1.2 RF yet, since it’s been out for a while now. Is it due to so many copies being out on loan, so you don’t have enough for a test sample? Is it something to do with the fact that it’s so complicated (referencing your build tear down)? Is it something to do with Canon in general? I suspect it’s something similar to my first question, but would love to hear why!

  • David Kudell

    Another great Sigma lens. Alas, the focus by wire system kills it for me, since I need to use it for video.

  • At first I was like, “it’s a good thing I published my Tamron review already, because I just called it the best 35mm EVER for astro-landscape panoramic stitching with its amazing corners, and now here comes a likely better lens…”

    …Then I saw the MTF graph and I was like, “NO WAY OMG!!!”

    😛

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