Camera Lens Reviews
Sigma 20mm f/1.8 EX DG Lens Review

By Scott Umstattd

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Sigma 20mm f/1.8 EX DG Lens Review
The Pros

A Unique Lens - No other lens at 20mm has a wide aperture of f/1.8. This alone makes the Sigma 20mm f/1.8 EX DG unique and compelling. Using the lens at f/1.8 will allow you to get more light through this lens than its competitors. And this is critical when shooting in low light.

Build Quality - This Sigma lens is well-built. It feels solid and well balanced on my Canon EOS 60D. And frankly, it looks good too. I don't have any real complaints about the sturdiness of the Sigma 20mm f/1.8 EX DG lens. If I threw it against a brick wall, I doubt it would shatter. It would probably not work anymore, but it feels strong enough to stay together if I did something that stupid to it.

Image Quality - Once you stop this lens down to f/2.8 or f/3.5 the image quality is sharp. Does it have world class image quality? No, it doesn't. But then again this lens does not cost as much as other lenses that do bring in exceptional image quality.

Focus - The Sigma 20mm lens auto focuses well. It's accurate and fast enough for most situations if plenty of light is available. It also has a very close focal distance of 2.6 inches. Getting in this close will help you create some great bokeh in your pictures. Something that is naturally challenging for any wide angle lens.

Low Light Performance - This is probably the main reason to buy the Sigma 20mm f/1.8 EX DG lens. F/1.8 is going to come in very handy if you are shooting weddings or in other low light situations. It's also a handy lens to have around if you are shooting video with your DSLR camera for the same reason.

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Sigma 20mm f/1.8 EX DG Lens Review
The Cons

Image Quality - Images are soft and not very impressive when stopped down to f/1.8 which is ironic because this feature is supposedly the main reason to buy this lens. Since it produces very soft pictures at f/1.8 it forces you to shoot at f/2.8 or f/3.5. This is a conundrum and part of what makes this lens so contradictory. But in the lens' defense, all lenses get sharper when you stop them down a step or two from their widest aperture. 

Auto Focus - While it does focus well in good light, with my experience the Sigma 20mm f/1.8 EX DG tends to search when confronted with a lack of light. Again, another contradiction for a lens thats main selling point is its wide aperture. Additionally, this lens is rather noisy when auto focusing. 

Filter Size - The Sigma 20mm f/1.8 requires 82mm filters if you want to use a UV filter, polarizing filter or any other kind of filter on this lens. And 82mm filters can be costly.

Lens Flare - The Sigma 20mm f/1.8 EX DG doesn't do a very good job of blocking lens flare cast by the sun or strong studio lights. This can be overcome by not pointing it in directions that highlight this weakness.

Vignetting - The Sigma 20mm f/1.8 EX DG does not prevent vignetting very well. This will cause light fall off around the corners. Stop it down (increase your f/stop) and vignetting gets better. 

Prime Lens - It's a prime lens, therefore you cannot zoom in or out when needed. This isn't necessarily a bad thing, but when added to the other draw backs and considering what other wide aperture, wide angle zoom lenses can do, I do consider it a con. Though not the worst of cons.

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Why Buy The Sigma 20mm f/1.8 EX DG?

I bought this lens in used condition. I bought it because at the time I did not have any wide angle lenses and I wanted one that would work well in low light situations. Most of the work I do is news/documentary-style and I often find myself in poorly lit areas in a run-and-gun situation. 

I get the most use out of my Sigma 20mm f/1.8 EX DG these days when I shoot video with my Canon 60D. While other lenses can satisfy your low light needs most of the time, the Sigma 20mm f/1.8 EX DG comes in pretty handy when shooting video with a DSLR camera. Especially in low light.

Since purchasing this lens, several other lenses have come and gone from my photography camera bag. I've used the Canon EF-S 15-85mm f/3.5-5.6 IS USM, the Sigma 17-50mm f/2.8 EX DC OS HSM and the Sigma 10-20mm f/4-5.6 EX DC HSM. All of which meant that my Sigma 20mm f/1.8 EX DG saw less and less time out in the sun.

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Show Me The Pictures!

Words are cheap. Here are some pictures taken with the Sigma 20mm f/1.8 EX DG lens.

The Sigma 20mm f/1.8 EX DG let you focus very closely and it easily blurs the background creating nice bokeh.

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Austin, TX at sunset with my  Sigma 20mm f/1.8 EX DG lens.

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The Sigma 20mm f/1.8 EX DG is a great low light option for wide angle shots.

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The Sigma 20mm f/1.8 EX DG lens took this picture of a nice home on a lake.

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At f/1.8 the depth of field become very thin. Notice that the tire and the front grill are in focus but the front corner of the toy car is out of focus. That's a pretty thin depth of field!

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With a wide aperture of f/1.8 it's easy to blur the background with the Sigma 20mm f/1.8 EX DG lens.

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The  Sigma 20mm f/1.8 EX DG  is a great wedding lens if you are looking for f/1.8 at an affordable price. Stop it down (increase your f/stop) and it takes sharp pictures.

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The Sigma 20mm f/1.8 EX DG lens hold colors well and lets you bring a big scene into your frame. Stop it down and you greatly improve vignetting. 

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Sigma 20mm f/1.8 EX DG Lens Review
Conclusion

The Sigma 20mm f/1.8 EX DG is not a terrible lens. It does have some pros that make it stand out. But in the end, I would not recommend this lens unless you find it at a price you simply cannot walk away from. I would recommend some other lenses before I recommend the Sigma 20mm f/1.8 EX DG lens.  For example:

Depending on your specific needs, you might want to consider the Sigma 17-50mm f/2.8 EX DC OS HSM lens, the Canon EF 16-35mm f/2.8L USM lens or the Canon EF 20mm f/2.8 USM lens.

If you do not need a fast aperture and still want a wide angle lens the Canon EF-S 15-85mm f/3.6-5.6 IS USM and the Sigma 10-20mm f/4-5.6 EX DC HSM lens are two great lenses I can vouch for.

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What Do You Think?

I hope this lens review has been helpful.  Got any personal experience with the Sigma 20mm f/1.8 EX DG lens?  Please leave comments and feedback below. 

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