Review: SIGMA 20mm F1.4 | A by Kishor Krishnamoorti

Kishor Krishnamoorti : Earlier last year, representatives of Sigma got in touch with me and offered to give me a lens for a couple of weeks as a trial. I already own a Sigma 50mm f/1.4 ART  and was keen on trying out their wide angle lenses. I settled upon the 20mm f/1.4 and took it with me for my trip to London in November. Here are my impressions of the lens.

Focal Length & Aperture

The Sigma 20mm f/1.4 is the world’s first 20mm lens with a 1.4 aperture. This is in itself a remarkable feature that sets it apart from all the other 20mm lenses available. Both Canon & Nikon only have 20mm lenses with an aperture of upto 1.8. The folks at Sigma have done some serious R&D work to come with this one-of-a-kind lens, marrying a wide focal length with a very wide aperture.

Image Quality & Distortion

I tested the lens at various apertures but was particularly interested to see the sharpness wide open i.e at f/1.4. While it is slightly soft wide open, the sharpness improves drastically as you stop it down and becomes tack sharp at f/8. Shooting in the streets of London during the daytime lead to some very sharp images since I had the flexibility to choose a narrow aperture.

The lens has little distortion for its wide angle focal length (as can be seen in the above image). While in London, it was tempting to point the lens upwards and capture the vastness of the skyscrapers. However, I’d often end up skewed lines and had to rely on Lightroom’s straightening tools to fix them. It did an amazing job but you do end up losing a decent part of the image in the cropping, as you can see below. Eventually, I factored for this loss of image during the capturing  time and composed the image with extra space on all sides.

Build Quality & Focusing

Having owned the 50mm series lens for a while, I was very impressed with the build quality of it and had a similar expectation for the 20mm. It didn’t disappoint and is built with the same materials as the rest of the ART series lenses. The graphite grey finish is beautiful and the ribbed body ensures a strong grip on the lens when transporting/changing lenses.

The lens is fairly compact and I didn’t find it too heavy while carrying it around in my bag (unlike the new Sigma 85mm f/1.4 which is an absolute monster sized lens!). Since it has a bulbous front element, it comes with a fixed lens hood to protect the front element. This does mean that it also comes with a proprietary lens cap so make sure you don’t lose the cap because it would be hard to replace.

I used it with my Canon 5D Mark IV and found the focusing to be silent and fast. Traditionally, I don’t worry too much about focusing with wide angle lenses as it is easy to get everything in focus with a narrow-ish aperture. But with this lens and its unique 1.4 aperture, you can end up with a narrow depth of field shooting wide open. And therefore, it is important to get the focus right otherwise you’ll end up with a lot of areas out-of-focus, as you can see in the below image.

Real World Applications

I found that 20mm is too wide for practical street photography and came handy only in particular situations. The below image would have been difficult with a 35mm lens but the 20mm proved perfect to capture the full vertical length of the mannequin from a close working distance. The lens really shines at night-time when you can make the most of its wide aperture and capture situations at low-ISO/high shutter and have sharp usable images.

Astrophotographers would also appreciate this lens, especially due to its combination of a wide aperture and a wide focal length. Another situation where I can see the lens prove its worth would be a crowded Indian weddings where I am squished from all sides with barely any room to capture the couple. With this lens, I would be able to comfortably capture both of them in the frame and not worry too much about the distortion either. Additionally, I can also isolate them from the background quite effectively with the wide aperture.

On the other hand, if you are using a crop sensor body (Canon EF-S or Nikon DX format), then this lens would provide an effective focal length of 30mm. I know a few photographer friends who love shooting street at 28mm (on a full frame body) so this lens would give a similar focal length when paired with a APS-C body.


The 20mm is a fabulous lens and very well priced. The build quality (as with all Sigma ART series lenses) is stellar and the image quality is second to none in this focal length. While the wide focal length might not be for everyone, the lens will definitely find a place in the bag of professional photographers who find a need for a high quality wide angle lens.


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