Sigma 20mm f/1.8 EX DG Lens Review

This is a review of the Sigma 20mm f/1.8 lens. It is the widest, large aperture prime lens on the market and is a very cheap alternative to the Canon and Nikon 24mm f/1.4. Although this lens is great for the  money you pay, it is obviously in a different league than the respective 24mm’s. It is worth noting that this lens can be purchased for very cheap on ebay (I got mine at ~40% off!), but keep in mind that Sigma lenses can frequently have quality control issues. This lens is no exception and I am sure that if you are reading this you have already read other reviews that talk about soft spots even when stopped down on some “dud lenses.” Having said that, buy from somewhere with a good return policy and you wont be disappointed.

Overall review: 8/10


  • Good build quality
  • Good value for money
  • Great color rendition and contrast when stopped down
  • Clever manual focus to AF clutch mechanism
  • F/1.8!!!



  • HUGE filter thread (non-standard size of 82mm?!)
  • Soft corners while wide open
  • Could be sharper when wide (it isn’t too bad in my opinion)
  • Comes with a cheap lens cap!


To buy this lens for a Canon mount, you can use this link.

To buy this lens for a Nikon mount, you can use this link.

To see sample pictures, look here.


One response to “Sigma 20mm f/1.8 EX DG Lens Review

  1. I’ve had this lens for a couple of days and have shot in a variety of situations. The image is somewhat soft at f/1.4, but sharpens quickly as you stop it down — f/1.8 looks much sharper and f/2 is excellent.From a purely practical standpoint, you can shoot in lower light w/o external lighting, and you can run higher shutter speeds in low light for better action-stopping when shooting people or animals. I was also amazed at the incredibly small depth of field I could attain — for example, I was able to narrow the focus down to a single stem of a plant and have every other part of the plant far out of focus. Not something I’ve been able to do with my Canon 17-85mm and 10-22mm zooms.It’s a heavy lens but it balances well on a 20D. Autofocus seems nearly as fast as with my Canon lenses. My one complaint is that the focusing mechanism (in auto or manual) isn’t as smooth or quiet as with my Canons — it sounds a bit rough in auto, and makes a slight “barking seal” sound as you go from close to distant focus manually.Nice of Sigma to include the lens hood and case, instead of charging exhorbitant amounts for the hood as Canon does.Overall, this is a very useful addition to my zooms, and it will definitely allow me to get usable natural-light photos in situations where I couldn’t before.

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