Best Lens for Astrophotography
I personally hate reading long-winded articles that beat around the bush. Here’s the conclusion: the best ultrawide lens for landscape astrophotography that I’ve tested myself for my purposes is the Sigma 14mm F1.8 DG HSM. I use it at f/2.8 for the best quality.
Want a little less wide? Get the Sigma 14-24mm f/2.8 DG DN and zoom all the way in. The best 35mm for Milky Way photography is the Sigma 35mm f/1.4 DG HSM Art. If you only have 300 Euro to spend for a new lens specifically for astrophotography, get the Samyang 14mm f/2.8 ED AS IF UMC used; the one with the gold ring.
Yes, I realize there’s an awful lot of Sigma and Samyang on this shortlist and no, I’m not sponsored. Not only do third party lens manufacturers make the best glass for this job, they fit most modern cameras.
If you want to know how I got this information, I invite you to read along with me. This article is a labor of love; an ode to the chase of the perfect lens that renders stars as points. But boy, this project got out of hand. And I might dislike reading long articles, but I sure seem to appreciate writing them. Let’s get into the weeds.
Astrophotography or Nightscapes?
What is the best lens for astrophotography? To answer that question, we have to make a distinction between deepsky astrophotography and landscape astrophotography.
Deepsky astrophotography is about shooting nebulae, other galaxies and to some extent even imaging solar system objects. Longer lenses and telescopes are used and often specialized cooled monochrome cameras and narrowband filters.
Landscape astrophotography includes having a foreground. Wider lenses are used and this is done with DSLR or mirrorless cameras.
Shooting nightscapes is not exactly the same as general low-light photography either. Our subjects tend to stay still, whereas low-light photography is often thought of as photographing everyday subjects like people. Landscapes in low ambient light could also inhabit that same space, but that’s a different ballgame. We’re not only talking long exposures and large apertures, but high ISO values too.
Since I’m a landscape photographer, we’ll be reviewing lenses that are best suited to shoot landscapes at night, or nightscapes. What we’re reviewing is very clear: we’ll be shooting the Milky Way and/or the northern lights in the dead of night, probably with some part of a landscape included to illustrate the relationship between the Earth and the heavens.
Choosing the best lens for Nightscapes
Landscape astrophotography or shooting nightscapes, is a very specialized subgenre of landscape photography that almost requires unique camera gear. Apart from a modern camera that can keep noise levels low at high ISO settings and of course a sturdy tripod to make sharp images possible, the lens choice is what makes or breaks a quality image. And there’s a whole subset of things to consider. Here are the 3 most important factors to look out for if you’re in the market for a nightscape lens:
Big aperture: An aperture that opens up to f/1.4 has more light-gathering potential than an f/2.8 lens. And, because its barrel is physically wider, there should be less vignetting. A lens with a big aperture can also be stopped down more to increase the image quality, as wide-open lenses tend to exhibit defects that hinders the rendering of stars well.
Wider focal length = better? It entirely depends on the subject and goal you have in mind. I find that photographing the Milky Way looks more dramatic when shooting with a 24 or even 35mm lens, while the optical distortion of a 14mm can lead to very dramatic foregrounds. Especially when you have a lens that focuses closer.
Low optical aberrations: Coma, astigmatism and chromatic aberration lead to elongated, warped and discolored stars. We don’t want that. Last but certainly not least, if the stars in the image center are in focus, we also want stars in the corners to be in focus, so the field curvature must be flat.
Disclaimer
For this article, I will present a vast majority of lenses that I have not tested in the field myself. But aside from the results in this test, we’re spending more attention on lenses that I actually have used for several years.
To give advice on any best lens list, we don’t need to regurgitate research that has already been done by people who make a living out of that. So that’s why you won’t see reviews for every lens on my website.
Lab tests as well as field tests do say a lot about the considerations for good lenses. You just have to find the data online and know which features you are looking for. So I will be presenting a meta review of the lenses that, on paper, are the best contenders. The best ones of that preselection, I’ll review myself. And I’m very critical.
This article is not sponsored, supported or endorsed in any way by any lens manufacturer or distributor. My opinion stated in this article is my own and there is no monetary gain or loss for voicing my opinion.
Sources
I’ve looked at tons of images and reviews from Lenstip, Cameralabs, DPReview, Optical Limits and Photography Life. But I also crawled more specialized websites such as Cloudy Nights to specifically look for cropped images of the corners to check for lens defects. It came to my attention that, while a treasure trove of info, Ian Norman of The Lonely Speck has a lot of lenses that fit Sony cameras, while I have shot Nikon and now shoot Canon. I have also found that some third party lenses fit only the Sony E-mount. One such lens was the Sigma 14mm 1.4 DG DN. Anyway, we’re not looking at any particular mount, but since I was a Nikon shooter for more than ten years and only recently have come back to Canon, I think I’ll bring additional information to the table to make an educated choice fot a new lens.
Great, now it’s time for big words. Let me tell you what they mean and why it matters.
Lens aberrations
No lens is perfect optically. It’s extremely hard and time consuming to approach perfection. Here’s what plagues my nightscapes in no particular order.
Astigmatism
Astigmatism in lenses comes in two bitter tastes. Either one can ruin an otherwise perfect star field. Not the Bethesda game. That was already ruined from the start.
Sagittal astigmatism makes stars look like they’ve sprouted little wings, stretching out in a direction perpendicular to the image center. Tangential astigmatism, on the other hand, pulls stars into streaks that radiate outward from the center like some rendition of warp or hyperdrive, depending on your taste in sci-fi. Neither is what you want when you're aiming for pinpoint stars.
Field curvature, lens centering & distortion
Field curvature is another subtle offender. Ideally, your lens should focus all points in the image on the same flat plane; your sensor. But with field curvature, the focus shifts across the frame, so stars in the center might be sharp, while those near the edges are blurry and distorted. This makes you feel like you're shooting through a fishbowl, and the only ways to correct that are to stop down the aperture or focus stack.
Distortion means that the image appears warped or distorted, meaning that stars appear to have different shapes across the image field. Distortion can more easily be corrected in post.
Having a lens that is decentered is related to these problems, where you could have sharp stars on one end and bigger, blurry ones on the other. That’s due to the lens not focusing accurately across the frame. One or more elements might not have been placed well inside the barrel.
Chromatic aberration
Then there’s chromatic aberration, the bane of accurate color rendition. This lovely little defect splits light into its component colors as it passes through the lens not unlike a prism, giving you colorful halos around stars—think red, green, or blue fringes that shouldn’t be there at all. Blue and especially red stars are welcome, as most of them should be either that or yellow. Purple and green stars do not exist. It’s especially noticeable when shooting wide open, and it can turn your pristine Milky Way into a rainbow of regret.
Coma
Coma is the optical flaw that turns your sharp stars into tiny, streaking comets, especially near the edges of your frame. It occurs when light from a point source, like a star, doesn't focus correctly as it passes through the lens, causing the light to spread out into fan-shaped distortions rather than a single point. This aberration is most noticeable at wide apertures and can make your stars look like they’re racing away from the center of your image, creating a distracting effect that’s the last thing you want in astrophotography.
In reality though, any combination of these lens defects is present in any lens to varying degrees, leading to complex aberrations that in the end render stars in awkward ways.
Vignetting
A small amount of vignetting can be helpful. I add it to most of my pictures in a controlled fashion. But when it’s already present in the lens, it’s harder to control. Sure, you can apply lens profiles corrections, but you have to be mindful of the fact that these have been generalized from dozens of samples, not your lens in particular. That means it corrects vignetting well enough in most cases, but if photographing the night sky, vignetting can be as distracting as any other defect. It’s one of those defects that I don’t have strong feelings against personally, but less is better for astrophotography.
What we do want in a lens for landscape astrophotography
Now that we’ve established what we don’t want, let’s talk about what we do want.
A wide aperture and short focal length
The defining attribute of a lens suited for nightscapes is how much light it gathers. A lens used for shooting the Milky Way or the northern lights is also as wide as possible while still collecting light like a Dutch tourist on a Greek island. We’re looking at lenses of 35mm wide or wider (on a full-frame camera) with an aperture of f/2.8 or larger.
Other lens features that are good to have
A lens that’s versatile simply offers more bang for your buck. Features that I’m always looking out for are autofocus, weather sealing and other potential daytime boons. All of this will jack up the price of the lens.
Autofocus
We’re not looking for a lens specifically with autofocus. The reason for that is that it’s so dark that most cameras have a hard time focusing in the absence of light anyway. And yes, I’ve tried autofocus on stars with my Canon R5. In none of the lenses tested was I happy with the accuracy, which has me doubting whether or not the autofocus is accurate enough for daytime photography.
That being said, I have a particular use case in which I do use autofocus in nightscapes. I use in-body focus-bracketing at twilight. Focus-bracketing without manually adjusting the focus ring for each frame has not only sped up my workflow significantly, but made the results much better too. I use this technique as an add-on for twilight blends, where I shoot my foregrounds during twilight, and expose for the night sky once astronomical twilight has ended. That combination has led to my best images and it even won me awards.
Weather sealing
Of course you’re not shooting in the rain at night, but do be aware that condensation is a real issue in any form of astrophotography. Having rubber gaskets at every moving and connecting part, is great to have. Especially in the long run, as fungi love moist environments. Still, I’ve had lenses that did develop fog inside of it despite weather sealing. One of 300 Euro, one costing 3000. Weather sealing can help, but to prevent condensation, it’s all in the way we prepare for temperature changes. And I learned that the hard way.
Is it a daytime lens too?
If the same lens can be used during the day, I could bring less gear with me on a trip. With 15 years of landscape photography under my belt, I’ve come to realize that the perfect lens for both landscape astrophotography and landscapes in general is not the same one.
But if the nightscape lens is very usable during the day, I’ll probably use it more. So that could covers the previous points I mentioned: autofocus and weather sealing. But a nice sunstar at minimum aperture, a close minimum focus distance, low focus breathing, low flaring and of course sharpness throughout the image frame at medium apertures are things to consider too. Here are my considerations for the best lenses for landscape photography in a previous blog post.
Summary: Important features for good nightscape lenses
The best lens for astrophotography…
…has an aperture as big as possible, while having…
…a focal length as short as possible.
Low to no lens defects that causes optical aberrations at a big aperture, making stars look funky.
My experience with nightscape lenses thus far
During these 15 years I’ve owned, loaned, rented and tested countless lenses. And I’m not even professionally testing gear. Some of which made decent enough candidates for landscape astrophotography too. Here’s a summary of lenses that I have actually used over the years to create pleasing images in what is hopefully a chronological order:
Canon EF-S 10-22mm f/3.5-4.5 USM
My first lens that I got while I had the Canon 550D/T2i. I didn’t know much about lens aberrations back then, but I found it too dark for Milky Way photography, so I got the…
Samyang 14mm f/2.8 ED AS IF UMC
"The Dark Rift" - An image that I'm not too happy with today, but that's because of my lack of post-processing skills so many years ago.
The Samyang 14mm was my first full-frame lens. More on this particular lens later, because I’ve tested another copy. Back then, I upgraded to the…
Tamron SP 15-30mm f/2.8 Di VC USD
"Sky Geist" - One of the most complex images to post-process in my career shot at 15mm on the Tamron 15-30. I focus stacked this by hand in the dead of night with moving icebergs.
Ahh, the decentered, poor quality control lens. I do not have fond memories of this lens. Shooting horizontal, the left side was in focus and the right side completely out of focus wide open. This could only be remedied with focus stacking or stopping down to f/8 or lower. As a result, stars in nightscapes were soft on one side, both at the short and long end of this zoom. I doubt that every copy has this issue, but mine did. That’s why instead I got the…
Nikon AF-S Nikkor 14-24mm f/2.8 G ED
"Chasing the Night" - As my post-processing skill increased with practice, I got into tracking as well. Here I used the Fornax Mounts LighTrack II for the sky. I shot the foreground at twilight. Both with the Nikon 14-24.
I said goodbye to this lens after bringing it up to the Dolomites and using it in pristine dark skies. At 14mm, the stars in the corner look out of focus and deformed. Mind you that I did achieve critical focus in the center. This lens did not produce a flat field. It could be for a variety of optical reasons. I traded it in and got the…
Sigma Art 14-24mm f/2.8 DG HSM
"Circe Poisoning the Sea" - Twilight blend of the aurora over Diamond Beach, shot with the Sigma 14-24 at 14mm.
The Sigma 14-24mm was my go-to wide-angle on the Nikon Z platform. Using the FTZ-adapter, this was one of the most practical lenses that I have photographed with. At night, it offers great results at 24mm that give most primes a run for their money. But at 14mm, the results are less spectacular, with heavy vignetting, spherical aberration and sagittal astigmatism. One thing that made this lens great for me was its short minimum focus distance. That allowed me to shoot insanely close to the foreground using focus stacking:
Please note that all the photos shown above are heavily edited and are for illustration purposes only. I often use a tracker as well to get that much detail out of the Milky Way. To judge the lens on its merits, please refer to these crops instead:
This just goes to show that even with less than optimal gear, you can still make great art. You don’t need the latest, the greatest or the most expensive glass. Which is why, contrary to what this article suggests, I’m not a gear head.
The best astrophotography lenses | Research
Let’s get all the lenses that I think are good candidates for nightscapes I have found online into a table. Lenses listed are a cross reference of all the sources I’ve mentioned in the introduction, limited to 35mm and wider, for full-frame cameras. Star quality is a subjective index of the roundness and sharpness of stars at f/2.8, where 1 is abysmal, 10 being perfect. Vignette quality is how well vignette is controlled in stops of light. Closer to zero is better. These have been pre-selected already. Lenses which It thought weren’t good candidates at all are omitted.
|
Lens |
Mount |
Aperture |
Focal Length |
Star Quality at f/2.8 |
Vignette at f/2.8 |
|
Irix 30 mm f/1.4 |
EF, F, K |
1.4 |
30 |
9 |
-.12 EV |
|
Irix 15 mm f/2.4 Blackstone |
EF, F, K, E, FE |
2.4 |
15 |
5 |
-.73 EV |
|
Canon EF 35 mm f/1.4L USM |
EF |
1.4 |
35 |
3 |
-1.3 EV |
|
Canon EF 35 mm f/1.4L II USM |
EF |
1.4 |
35 |
7 |
-0.21 EV |
|
Canon EF 35 mm f/2 IS USM |
EF |
2 |
35 |
4 |
-1.67 EV |
|
Canon EF 28 mm f/2.8 IS USM |
EF |
2.8 |
28 |
3 |
-0.9 EV |
|
Canon EF 24 mm f/2.8 IS USM |
EF |
2.8 |
24 |
3 |
-0.98 EV |
|
Canon EF 24 mm f/1.4L II USM |
EF |
1.4 |
24 |
2 |
-0.25 EV |
|
Canon EF 14 mm f/2.8L USM II |
EF |
2.8 |
14 |
2 |
-0.7 EV |
|
Canon EF 16-35 mm f/2.8L III USM |
EF |
2.8 |
16-35 |
4 |
−1.17 EV - −4.07 EV |
|
Venus Optics LAOWA Argus 28 mm f/1.2 FF |
E, Z, R, FE, L |
1.2 |
28 |
4 |
-1.45 EV |
|
Venus Optics LAOWA Argus 33 mm f/0.95 CF APO |
E, Z, R, X, FE-M |
0.95 |
33 |
5 |
-0.71 EV |
|
Venus Optics LAOWA 15 mm f/2 ZERO-D |
M,E, Z, R, FE, L |
2.8 |
15 |
2 |
-2.65 EV |
|
Venus Optics LAOWA 12 mm f/2.8 ZERO-D |
EF, E, Z, K, R, A, FE, L |
2.8 |
12 |
3 |
−3.54 EV |
|
Nikkor Z 20 mm f/1.8 S |
Z |
1.8 |
20 |
3 |
−1.31 EV |
|
Nikkor Z 24 mm f/1.8 S |
Z |
1.8 |
24 |
4 |
−1.24 EV |
|
Nikkor Z 35 mm f/1.8 S |
Z |
1.8 |
35 |
4 |
−1.15 EV |
|
Nikkor AF-S 20 mm f/1.8G ED |
F |
1.8 |
20 |
4 |
−0.94 EV |
|
Nikkor AF-S 24 mm f/1.4G ED |
F |
1.4 |
24 |
2 |
-1.17 EV |
|
Nikkor AF-S 24 mm f/1.8G ED |
F |
1.8 |
24 |
3 |
−0.94 EV |
|
Nikkor AF-S 28 mm f/1.4E ED |
F |
1.4 |
28 |
4 |
−0.64 EV |
|
Nikkor AF-S 28 mm f/1.8G |
F |
1.8 |
28 |
1 |
-1.07 EV |
|
Nikkor AF-S 35 mm f/1.4G |
F |
1.4 |
35 |
2 |
-0.24 EV |
|
Samyang AF 14 mm f/2.8 EF |
EF |
2.8 |
14 |
4 |
−3.17 EV |
|
Samyang XP 14 mm f/2.4 |
EF, F, E, FE |
2.8 |
14 |
4 |
−1.30 EV |
|
Samyang 35 mm f/1.4 AS UMC |
EF, F, A, K, MFT, NX |
1.4 |
35 |
3 |
−0.64 EV |
|
Sony FE 14 mm f/1.8 GM |
FE |
1.8 |
14 |
2 |
-1.71 EV |
|
Sony FE 20 mm f/1.8 G |
FE |
1.8 |
20 |
4 |
−1.94 EV |
|
Sony FE 24 mm f/2.8 G |
FE |
2.8 |
24 |
6 |
-3.02 EV |
|
Sony FE 28 mm f/2 |
FE |
2 |
28 |
1 |
−1.84 EV |
|
Sony FE 35 mm f/1.4 GM |
FE |
1.4 |
35 |
9 |
−1.63 EV |
|
Sigma A 20 mm f/1.4 DG HSM |
EF, F, Sigma, E, FE, L |
1.4 |
20 |
4 |
−0.70 EV |
|
Sigma A 24 mm f/1.4 DG HSM |
EF, F, Sigma, E, FE, L |
1.4 |
24 |
1 |
−0.71 EV |
|
Sigma A 28 mm f/1.4 DG HSM |
EF, F, Sigma, E, FE, L |
1.4 |
28 |
5 |
−0.68 EV |
|
Sigma A 35 mm f/1.4 DG HSM |
EF, F, Sigma, E, FE, L |
1.4 |
35 |
9 |
-0.79 EV |
|
Carl Zeiss Batis 18 mm f/2.8 |
E, FE |
2.8 |
18 |
6 |
−2.63 EV |
|
Carl Zeiss Otus 28 mm f/1.4 |
EF, F |
1.4 |
28 |
4 |
−0.84 EV |
|
Carl Zeiss Batis 25 mm f/2 |
E, FE |
2 |
25 |
3 |
−1.75 EV |
|
Carl Zeiss Distagon T* 25 mm f/2.0 ZE/ZF.2 |
EF, F |
2 |
25 |
2 |
-0.39 EV |
|
Carl Zeiss Distagon T* 35 mm f/1.4 ZE/ZF.2 |
EF, F |
1.4 |
35 |
1 |
-0.2 EV |
About third party lenses
This is the most exciting category to me. Not only because there are often multiple mounts available, but third party manufacturers create some of the most stunning glass to outperform camera brands by some margin. Their only downside is artificial: they’re not as popular as Canon, Nikon or Sony and as a result will lose you money if you decide to sell them. The solution? Just don’t sell them.
Lenses not considered
So why not include other lenses in this test? Several reasons.
I’m not filthy rich, so I can’t purchase every lens under the sun. Even if it’s for testing and returning within a grace period.
I don’t have contacts at every distributor or manufacturer to do this for free.
This test took 2 weeks of my time.
I have done significant desk research to conclusively say that some lenses don’t need additional testing from me; they’re simply not suited for astrophotography at all.
I don’t have all the platforms to test lenses on. I’ve shot a few Canon cameras, half a dozen Nikons and on one occasion I took a Hasselblad X1D II 50C to Iceland.
Testing 7 astrophotography lenses myself
After researching the web for months to achieve the table above, I ordered four wide-angle lenses with the best reviews for photographing stars. The idea here is to test them myself before making final recommendations on which lens actually renders the very best stars. That was a few weeks before posting this. Then three more lenses followed.
One of the very first lenses that I got specifically for shooting the night sky, was the Samyang 14mm f/2.8 ED AS IF UMC. A lens that got several makeovers in the meantime, so I figured: let’s pit the OG Samyang 14mm against the one that has the best theoretical performance: the Samyang MF 14mm F/2.8 MK2. None of the other 14mm lenses by Samyang (which sell under the name Rokinon in the US by the way) are contenders.
Then I thought: why stop there? Another lens that was on my list after all the research that I had done finding the perfect nightscape lens, is the Sigma 14mm F1.8 DG HSM. Not exactly the 1.4 monstrosity, because the Sigma 14mm F1.4 DG DN only fits E- and L-mounts.
As I was ordering lenses for the test, I additionally came across a copy of the Samyang 24mm f/1.4 ED AS IF UMC, a light gathering bucket of a lens. Because it has a much tighter focal length as well as a larger maximum aperture, there is more potential to let light in from more distant and fainter stars.
A week or so later and I’ve invited the Irix 30mm f/1.4, the Sigma 35mm f/1.4 DG HSM and the Sigma 20mm f/1.4 DG HSM over for testing. That latter of which I’ve read wildly different things about, but as I see stocks getting lower, I think it’s not being made anymore either. We’ll see if this lens is worth buying used when we put it through its paces.
So here’s the list of lenses that I’ve tested, sorted by focal length, then age:
Samyang 14mm f/2.8 ED AS IF UMC
Samyang MF 14mm F/2.8 MK2
Sigma Art 14mm F1.8 DG HSM
Sigma Art 20mm f/1.4 DG HSM
Samyang 24mm f/1.4 ED AS IF UMC
Irix 30mm f/1.4 Dragonfly
Sigma Art 35mm f/1.4 DG HSM
Full-size images
Download all full-size images here. These images have not been edited, other than the attempt of removing a purple fringe around stars. We’ll start with an apples to apples comparison of all lenses at f/2.8. All images shot using a Canon R5 at ISO 400. Remarks will follow at the end.
All lenses at f/2.8
Aperture: f/2.8, Shutter speed: 4 minutes, 16 seconds
“It’s crazy to see the difference in color, contrast and even exposure.”
More light | All lenses at f/2
Some of these lenses open up to a wider aperture. Here are the results of those 5 lenses. Aperture: f/2, Shutter speed: 2 minutes, 8 seconds
Maximum aperture | All lenses at f/1.4
With the exception of the Sigma 14 HSM, these lenses open up to f/1.4. Here are the results with these lenses letting 2 stops more light in than at f/2.8. Aperture: f/1.4, Shutter speed: 1 minutes, 4 seconds
“At maximum aperture, these images look more similar.”
Crops
Traditionally, 100% crops are shared to illustrate how the lenses perform. I’ll zoom in way more due to the high resolution of the R5 I used to test these lenses. Now these are cropped from the exact same position of the image frame. After that, I’ll show you the shape of the stars.
Top left
Top right
Center
There’s no point in comparing the bottom corners as the wider focal lengths are drowned in light pollution.
“I have no idea why the Sigma 20mm looks so much brighter at the same exposure settings. I’ve checked to see that the aperture is actually working.”
Star shape comparison, top left
Let’s zoom in even more. I’ve tried to find the same star across images with comparable focal lengths.
Observations
Well, we have a lot to discuss here. It’s going to be a challenge for me to be concise and get my impressions across, as there are so many variables to consider.
Color rendition
There are two reasons for the full size images to shift color that much. First is that the conditions for shooting weren’t constant. The tracker rotated about 90 degrees from South to West as the night progressed. That means we see varying degrees of light pollution in the images. Also, the crescent moon rose in the east in the later half of the test. Furthermore, a thin layer of high clouds can be seen passing overhead in some images.
The other reason for color shifting is down to the optics. And I feel that there is a difference in how the lenses render colors, despite shooting condition not being identical. Mind you that the white balance and all other settings that could contribute to color are the same across all images. I think that this slight shift in hue and saturation because of the glass and coatings used can easily be tweaked in post to your liking. Now that we have that out of the way, let’s look at the other differences.
Samyang old versus new
The two Samyang 14mm lenses are very similar optically. They have similar vignetting and sharpness. The difference in the shape of the stars could be down to individual lens margin of error. I see more elongated stars, indicating tangential astigmatism in the original’s top right, whereas the weather-sealed MK2 has slightly more sagittal astigmatism. In the top left the roles are reversed, but very slightly.
Samyang vs Sigma 14mm
Comparing those Samyangs to the much more expensive autofocus Sigma 14mm 1.8, is perhaps not a fair comparison, but the differences in star rendering and especially vignetting are staggering. With the Sigma at f/2.8, I don’t notice vignetting at all. That’s probably because in the lens barrel, there’s much more physical space for light to travel through. There’s less color fringing and less color shifting, indicating that all waveforms of light gather at same spot. That’s an impressive feat of engineering, considering its 14mm focal length.
Sigma 20mm image quality for stars
As we move on to tighter focal lengths, the enormous butterfly of a star that the Sigma 20mm produces cannot be ignored. At 2 stops less than maximum aperture, no less. So sagittal astigmatism is playing a big part in the rendition of stars in this lens. We see softness of stars in the corners as well, giving the indication that there is significant field curvature or spherical aberration. That means that stars in the center may be in focus, but it’s a different story in the full-frame corners.
If we talk about Sigma’s 20mm f/1.4 some more, we have to discuss the positively crazy increase of light as we close the aperture. It’s so wild, that I’ve retested the lens over and over again at different shutter speeds - all images show exactly the same result. Compared to other lenses, the exposure is much brighter at f/2.8, which is more evident at longer exposures. Mind you, the exposure settings are all the same. It thought it would be vignetting, but that’s not whole story. Here’s a crop of the right side of the frame during a highly scientific lab test:
Samyang 24mm purple fringing
The Samyang 24mm has purple fringing around all stars. I cannot get rid of it by turning off in-camera Long Exposure Noise Reduction (LENR) as suggested by Peter Zelinka. Furthermore, it’s there at f/1.4 as well as f/2.8. For these images, I have applied profile corrections, checked remove chromatic aberration, added manual defringing and even lowered the hue and saturation of purples and magentas, hoping the stars will be more pleasing to the eye; to no avail on the brighter stars. The reason is that this lens has intense purple fringing around all high contrast objects even with LENR off. Check out these shots to confirm my suspicions:
Irix 30mm Dragonfly
The Irix 30mm has minor coma at the extreme edges of the frame at f/2.8, but that’s as wide as I would go with this lens for astrophotography purposes. There’s significant sagittal astigmatism at wider apertures and vignetting wide open is a problem. The red glow of the star underneath is the star’s natural color.
Sigma 35mm for Milky Way photography
Lastly, the razor sharp Sigma 35mm isn’t perfect either. At f/2.8 we see sagittal astigmatism in the extreme edges of the frame, albeit slightly. But what’s bizarre to me is that the Sigma 14mm looks about the same at these settings. At roughly the same price as the Irix 30mm, it’s a tough decision. The 30mm Irix has weather sealing, while the 35mm Sigma has autofocus.
Conclusion
Because of the results above, I’m considering keeping the Sigma Art 14mm F1.8 DG HSM and maybe the Sigma Art 35mm f/1.4 DG HSM. The 14 has weather sealing and both have autofocus, which is why the 14 in particular is a great daytime wide-angle lens too. Now I recently switched to Canon, so I’m in the process of getting lenses that fit the EF-mount. But if you have any of the lenses on this list already, you’re not going to get 80% better nightscapes by getting a lens that performs 20% better. That’s all down to your approach in the field and in post-processing nightscapes. This link will take you to my 5 hour video tutorial on stacking, tracking and post-processing landscape astrophotography.
As stated before, I’m not sponsored or supported for having written this. I also don’t have affiliate links set up like most do. And there is no advertising on my website. Please consider learning more from me by getting a video tutorial if you feel this article has helped you. Gear will not make you a better photographer. Skills do.