Sigma 20mm F/1.4 Art Lens Review – Moonlit Night

The Sigma 20mm F/1.4 Art Lens is one of the fastest wide angle full-frame lenses available today, and certainly the most affordable in its class. I took the new lens for a spin at night and shot in near total darkness with a Sony a7S II.


I was really excited when the Sigma 20mm F/1.4 Art Lens was announced last month and released just a few days ago. It is easily one of the most intriguing lenses I have seen. Why? Because for me 20mm is a stunning extreme wide angle focal length and this lens brings us great image quality, worthy of 4K video and at the same time it is exceptionally fast.

With an open aperture of F/1.4 and with great performance the seemingly high price of $899 is surprisingly low and for me competes with the most professional lenses available.

Right click, open this image in new window to see it in full 3840pixel resolution.

Right click, open this image in new window to see it in full 3840pixel resolution.

With the introduction of the new Sony a7S II, we can now shoot brilliant 4K video in extreme lowlight conditions. As we found out just recently, this new Sony mirrorless camera is even more powerful in lowlight than its predecessor, the original a7S.

So there was no question when this lens arrived at our office I went out and shot the whole evening just with this lens and entirely at F/1.4. You can observe the result in the video above which I hope you will enjoy. For me it was a pure enjoyment I can tell you, to realize that I needed to get far out of the city in order to push this camera/lens combination to its lowlight limits. I walked through forests, empty parking lots and ended up at a castle and many times the only light source was the moon. I could not see what the camera saw, it was my “night vision device” and the sky was not (!) blue, as it appears to be in the video.


Coming back to the editing table I was very happy to find out that the Sigma 20mm F/1.4 Art Lens indeed performed very well at its lowest aperture. I pushed the camera to 25,600 and 51,200 ISO max, as in my tests I felt those were the breaking points when it comes to noise for an HD result. In terms of exposure I tried to expose “bright”. In lowlight it is important not to use the dark side of the spectrum too much, because this is where the noise is and it has to be cut off.

I shot everything in the Slog2 Gamma and graded the film with a “lowlight” LUT I created for this project, that retained most of the spectrum, lowered the dark areas and accented the highlights only slightl. I wanted to go for a low contrast look and I’m pretty happy with the result. I’ve heard otherwise, but personally I do recommend shooting lowlight in Slog2 as this for me is the perfect starting point for a balanced grade.


One thing I did notice about the Sony a7S II in lowlight is that there’s apparently some kind of “trick” going on in extreme lowlight. When I filmed my feet walking on grass I realized that there’s some ghosting introduced at ISO 51,200. In the shot below you can see multiple frames in one frame.


Ghosting effect at high ISO speeds on the sony a7S II

Either this is a result of some kind of internal “temporal noise reduction” (this is how it looks to me) that appears on fast moving objects and patterns OR it might also be a result of the low temperature I filmed at (-1 C°). I did not notice the effect in any other shots but this one.

How Good is the Lens?

For this Sigma 20mm F/1.4 Art Lens Review I used the EF version of the lens together with a Metabones Adapter on the Sony a7S II in both 4K video and stills mode. This is not a scientific lens test, because of the lack of reference lenses, but there are a few important things I could observe and want to show you about this lens.

While this lens / adapter / camera combination is really not ideal for stills photography I took photos with our high resolution test chart in order to see how good the lens performs on a quality 4K photo / video image.

Left: Sigma 20mm Lens @ F/1.4 | Right: Sigma 20mm Lens @ F/8.0

Left: Sigma 20mm Lens @ F/1.4 | Right: Sigma 20mm Lens @ F/8.0

The image above is a shot of our test chart in two different F stops. We can see quite a strong vignetting at F/1.4 in comparison to F/8.0. Personally I like vignetting and I often apply it to my shots in post, but it certainly also darkens your image further than you would like. This means that when you shoot wide open you must know that you are losing about half a stop of light due to vignetting.

Here we can also observe distortion, which, for a 20mm lens seems very low. These two attributes (vignetting and distortion) can be corrected in post, but sharpness and chromatic aberration is something that cannot be fixed with plugins, so these for me are the most important factors when it comes to lens quality.

Top-Left corner of the test chart to observe chromatic aberration and sharpness

Top-Left corner of the test chart to observe chromatic aberration and sharpness

Here’s a crop of the top left corner of the test chart shot at F/1.4 with the Sigma 20mm F/1.4 Art Lens. We can see of course that the leftmost edges of the shot are softer, yet at the same time the kind of sharpness to me is unlike other lenses I’ve seen shot wide open. Certainly a kind of sharpness absolutely pleasing and mostly sufficient for 4K. If you want a totally clean image, the softness goes away gradually when the lens is stopped down until about F/5.6.

In terms of chromatic aberration there is very little of that. Again absolutely stunning performance from this lens in comparison to other lenses I’ve seen. In my video I did not notice any chromatic aberration in any of the shots.

Build Quality

One thing you should know: This lens is not lightweight. With 960 grams it is lighter than your full fledged cine lens, but it is  double or triple the weight of other mirrorless prime photo lenses you might use for video. That said, the build quality is very nice. The lens feels solid and well made with no flimsy parts.

The focus can be set to manual and the lens has an analogue focus ring (unlike most Sony photo lenses). Unfortunately there are no hard stops making it hard to use the lens with any focus gears or focusing tools. Also the focus throw is very narrow and considering the lens has a thin depth of field it can be hard to focus manually at times. The lens is clearly design for the photographer in mind. This is a drawback we’re already used to as mirrorless and DSLR video shooters, but it’s not ideal for some applications and doesn’t provide the best ergonomics.


This lens kept its promise offering superb quality and while it is made for photography with some ergonomic drawbacks for video it is still among my favourite lenses of all time. The kind of shots I could achieve with this lens, without any noticeable quality loss is amazing and opens up new possibilities for people who like lowlight shooting. Furthermore this lens opens up your path to shallow depth of field at wide angles, which is rarely seen outside of high end professional productions.

The biggest highlight about the Sigma 20mm F/1.4 Art Lens for me is its price though. At $899 the value for money you get is very high and makes it an affordable option for shooters working with a Sony a7S II.

I hope you enjoyed this review. You can download the source video from Vimeo to take a closer look at the shots in HD. Let us know your own observations and thoughts about the lens in the comments.

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Kotlos Kotlos Reply
Kotlos Kotlos November 26, 2015

Thanks for the review.
Have you noticed the ghosting in any other shots above 51200? If it is internal processing it should be there. I can’t think of a way for temperature to create this effect.

 Stefan Sietzen Reply
Stefan Sietzen November 26, 2015

I think the ghosting might be caused by flickering fluorescent lights.

Chris Gibbs Reply
Chris Gibbs November 26, 2015

Good point, you can actually see this effect with many street lights if you view them out of the corner of your eye.

masashi sato November 26, 2015

Hi,good revew.nice lens.
but,…I wonder you use Movcam cage.
in past article(
Movcam cage for A7s is disappointed.
Is Movcam cage for A7s2 good ?
Is The camera locked on Movcam cage?

Please tell me.

Sebastian Wöber Reply
Sebastian Wöber November 26, 2015

Hi Masashi, will have a cage review very soon, please be patient, thanks.

masashi sato November 28, 2015

Thank you.I’m looking forward to the review.bye

Peter Vee November 26, 2015

Impressive lens. You don’t get more dynamic range with Slog in the dark. In fact you get the opposite. The Slog curve is king at bright and highlights, all you have to do is look at the Slog curve and how much data it can capture between each DR stop (fixed equal amount per stop). A typical night scene with street lamps has 5 stops of DR. Those 5 stops are on the arse-end of the Slog curve where it performs worse and gets crushed. A Cine Profile with Rec709 will capture more data over 5 stops (exponential amount per stop)

Sebastian Wöber Reply
Sebastian Wöber November 27, 2015

Hi Peter,
I understand your reasoning, but the benefits of Slog outweigh any scientific explanation that some people like to promote. For me Slog is the choice, no matter how dark the scene. It’s an artistic choice as well as an aesthetic one. I have studied the noise behaviour of these cameras very very well and for me Slog supports the way I want to expose my “digital film” in the dark.
Just one thing: I disagree that there is a “typical night scene” with 5 stops of DR. In fact at night I think you can possibly have even more need for DR than during the day.
All the best,

 KC Bassett Reply
KC Bassett November 29, 2015

I agree i use s-log2 at night as well and have got exceptional filmic results. There can be a need for a large dynamic range. Especially when i was shooting fire dancers at night and wanted to capture the most detail in the shadows as well as all the detail in the flames without them becoming over exposed.

Richard Oxford Reply
Richard Oxford November 27, 2015

Barnaby, deeeeecent

 Ash Tailor Reply
Ash Tailor November 29, 2015


Let me say what an excellent video that was. I loved the editing and especially the music, so kudos on making it and showing some awesome skill. Wouldnt be the internet if I didn’t ask – is it uploaded anywhere? Would love to check it out.

And, like I keep posting in the other thread, it does seem, overall that the a7rII is an overall better prospect and im sure you could’ve got 70% of the shots you filmed here with that too.

It’s a shame Sony have muddled the two.


Sebastian Wöber Reply
Sebastian Wöber November 29, 2015

Hey Ash,
Thanks for the comment on my work.
As I measured the a7R II 2 stops less powerful, I disagree though, that I could’ve got the same kind of shots (quality) from it.

 Ole Salomonsen Reply
Ole Salomonsen December 3, 2015

It dissapoints me how a “respected” source like Cinema5D can praise this lens, using words like “superb quality”.

This lens is not superb quality, it is not even close.
The Simga 50 1.4 ART and 35 1.4 ART was great quality, however Sigma failed to reproduce this quality in the 24 1.4 ART, with massive comas in the corners and CA across the frame.

Expectations where high for this lens given the weight, the size, and the willingness to abandon the option for filters.
Due to this I expected the lens to have stellar optics, but it fails, just like the 24mm 1.4 ART. In fact it might be even worse than the 24 1.4 ART.

This 20mm 1.4 ART lens suffers from severe field curvature distortion. This means that when you have the center sharp/in focus, the corners are soft, really soft. You can even see this clearly in you video at 01:56. And if you focus in the corners to get them sharp, firstly you get severe comas, where strong lightsources like city lights and stars, looks like bananas on fire, and center is not sharp. These optical shortcomings/distortions makes this lens unusable for astrophotography or shooting city lights in the dark, and makes it unsuitable to shoot in 4K, since the details are lost and/or destorted.

Of course people have different needs, and not all may be aiming at astro-photography or city-shots at night. But we allready have other fast wide-angle lenses for shooting portraits or people in shallow DoF.

Did someone say stop down? – Of course you do not buy this lens to stop down, you buy it to be able to use it wide open. It is expensive, and it does not deliver.

I know others are experiencing the same, so it was just not my sample. This lens is overrated and dissapoints.

The Nikon 20 1.8 is in a different class than this lens, it is much sharper across the whole frame, and comas are nowhere near as bad as on the Sigma 20 1.4.

Please do not give Sigma the good credit when they do not deserve it. And if you want people to take you seriously in your reviews, please make sure you have tested other similar lenses before you say it is normal for such fast wide angles to have this softness in the corners, because it is not.

Cinema5D, IMO this was not a good review of this overrated lens.

BTW I also shoot with the A7S2, as I shoot in the dark for a living. The softness this lens produces in the corners wide open is unnacceptable for any professional use.

 Ronn Murray Reply
Ronn Murray December 3, 2015

Well said and my experience was very similar to yours. I’ve seen toy lenses that outperform this lens.

Sebastian Wöber Reply
Sebastian Wöber December 3, 2015

Hi Ole, If you want a specialized astro-photography review for the lens, please go elsewhere. This review is about 4K video shooting and using the lens not particularly to shoot stars. Coma is irrelevant for most applications. As a whole I am convinced the lens is absolutely superb and I could not comprehend your criticism. By now there are numerous reviews by other respected websites that confirm my findings and rate the lens very highly. Just check Google. Thanks

 Ole Salomonsen Reply
Ole Salomonsen December 3, 2015

Really a mature way to respond. Getting ever more respect for you now.

If you forget about the coma, even the uneven focal plane of this lens wide open makes it fail for most uses. Field curvature distortion should be absolutely possible to avoid on a prime lens. Try the Nikon 20 1.8, obviously you have not tried it yet.

Your shot over the city is soft in the corners due to this lens. I am not wasting my time shooting in 4K using such a soft lens, and I am sure many others would like to know that this lens is actually really soft in the corners when in focus in centre wide open.

 Ronn Murray Reply
Ronn Murray December 3, 2015

One has to wonder if you actually shot any stars wide open with it as my findings were substantially different than yours. Huge focus fall off and terrible coma issues. Or perhaps your review is motivated by kickbacks on affiliate sales?

Sebastian Wöber Reply
Sebastian Wöber December 3, 2015

Hi Ronn, That is a pretty severe accusation. If you look at our reviews you will see that they are very critical and we don’t hold back on what we find. Please show us your lab test results, what you’re saying about the weak performance is simply not correct.
Regarding “shooting stars”, the lens has some coma issues wide-open which make it not ideal for astro-photography. Again, this is not an astro-photography website.
The lens is superb and other reviews confirm it.

 Ronn Murray Reply
Ronn Murray December 3, 2015


I don’t need lab tests. I need real world results and in the real world this lens is junk. Suggesting anything to the contrary when it’s clear in your video it doesn’t produce well with coma or focus is misleading at best and one can only question your motives. But if you must see results… Here ya go.

 Ronn Murray Reply
Ronn Murray December 3, 2015

In all fairness your video is titled Moonlight night with an image of a starry sky so to condemn others for faulting your findings and claiming it’s not about astrophotography is a bit shortsighted as well.

 Ole Salomonsen Reply
Ole Salomonsen December 3, 2015

My thoughts exactly, valid point IMO.

Sebastian Wöber Reply
Sebastian Wöber December 3, 2015

Ronn and Ole,
Again, that sample you posted is about Coma which I acknowledge, but it is not a complete review about the lens at all. Even though in my review there were stars in the sky, coma was in my opinion NOT a relevant issue for my film and not for most other projects I see people shoot. I loved the sharpness and chromatic aberration performance of the lens and think it is superb. These are the main issues most other lenses have wide open. If you don’t like the lens, because you’re doing astro-photography, please go for a different one, but there is no reason to trash my review, just because the lens doesn’t perform well in one niche aspect that is relevant to your specialized application, moreover for photography (this site is about video).
Filming a nightsky on a tripod is not a day-to-day use for a lens and when movement is involved as in my film, the edge sharpness of stars is (imho) quite irrelevant to the viewer. This is an outstanding wide angle lens with strong performance on the points relevant for videographers and will do a great job in 95% of all applications.

 Ronn Murray Reply
Ronn Murray December 3, 2015

You’d asked for feedback and we have honest feedback. I’m sorry if you see that as trashing your review. By the way, most of what we do if filming night scenes. Niche, perhaps but is t this a Niche lens that if it in fact was good at focus and didn’t have coma issues would be exactly THE lens for our primary subject? I’d love to see you test sharpness at infinity wide open and see if your able to still produce results to be so enthusiastic about.

Apostolos Nikolaidis Reply
Apostolos Nikolaidis December 7, 2015

Wow, I feel some tense here. Ronn & Ole I see your point but consider that this is not a scientific test for photographers but instead an overall impression of a photo lens for video usage. And there is nothing wrong if someone (and that someone is a professional, as many of us in here) is excited about a new product he has used and tested. And of course you can find better lenses but I doubt it in that price tag (which is what Sebastian emphasises in his post). I enjoyed the review and of course we will have to rent/try it first before investing as in anything else. And please don’t shoot the pianist. We’re all on the same side here..

Peter Vee December 7, 2015

What we have here is “style over substance”. Those in the substance camp are aware of this lens’s shortcomings because they are in a field where it is scrutinised and “it is what it is”…regardless of their niche. What must irk them is…at this price you should have a lens that satisfies both camps.

 Ole Salomonsen Reply
Ole Salomonsen December 8, 2015

I am pretty sure many of those 40K people who has read this “review” and watched this video, which are all potential buyers of this lens, would like to know how bad optically this lens really is.

I work with both stills and video, this lens performance wide open is unacceptable for both purposes, style or substance.

If only the lens was in focus all over the focus plane, like the Nikon 20 1.8 is wide open, I could probably live with some of the coma. But a brand new prime lens produced in 2015 which is simply suffering from severe field curvature distortion is unacceptable IMO.

What we all want is good optics. It is wrong to send out the wrong message, and give Sigma good credit, when this lens is under-performing.

Perhaps I will have to read every lens review from Cinema5D with a grain of salt in the future.

James Cook December 19, 2015

I really liked the image quality of this lens. I’m going to purchase it. What are some of your favorite cine lenses to use with the a7sii?

Sebastian Wöber Reply
Sebastian Wöber December 20, 2015

Depends. What application?

Márton Sári November 9, 2016

Nice test video, thanks. I think what was more beyond the limits is the shutter speed. I suppose it was auto, and the camera set it to the lowest possible, but a shutter speed lower than 1/48 or 1/50 sec produces too much motion blur, especially coupled with noise. It really adds a video-ish feeling.

Sebastian Wöber Reply
Sebastian Wöber November 10, 2016

Hi Marton. If I remember correctly the shutter was always set to 1/50th.