Sigma 20mm F1.8 EX Aspherical DG DF RF A-mount lens review by Bob Socko
|Bob Socko#7959 date: Sep-10-2010
flare control: 4
|I used to own this lens
|* Minolta 20mm f/2.8
* Sigma 24mm f/1.8
* Sigma 30mm f/1.4
* Sony 50mm f/1.4
|225 USD (refurbished)
|* wide angle without excessive distortion
* wide aperture makes low-light work possible
* VERY short MFD
* a much better performer than its sister lens, the Sigma 24mm f/1.8
* solid build
|* images have a yellow tone
* slow to focus
* soft corners wide open
* there are more versatile options for APS-C landscape shots
|I was pleasantly surprised by this lens's performance. Sharpness was on par with most fast primes, in that shooting wide open results in usable shots and stopping the aperture down results in great shots. Though the focus was a little slow, it was certainly fast enough for objects moving at reasonable speeds - say, a person walking down the street. Colors are a little more yellow than I prefer, though no worse than any other Sigma lens I've used, and it's easy to fix in post. The minimum focus distance of 20cm (8 inches) is fantastic; between that and the wide aperture, I suspect this lens would be useful when shooting crowded events.
Compared to the Sigma 24mm f/1.8, image quality at f/1.8 is substantially better. Images were sharper, there was far less CA, and the lens seemed to focus a little faster. That being said, I question how useful either lens is wide open - between the wide angle and a narrow depth of field, you risk losing a lot in the bokeh.
If you are an APS-C shooter and plan on using this lens primarily/exclusively for landscapes, you would probably be better off purchasing a good wide-angle zoom lens instead. For example, I can't image there's a significant difference between the image quality of this lens at f/8 and the Tamron 17-50mm f/2.8 when shot at 20mm, f/8. The Tamron is not too much more expensive than this lens and is far more useful for everyday shooting. So, unless you really need a wider aperture than f/2.8 (or are a full-frame shooter), you might as well pick up a decent quality zoom lens instead.