Sigma 20mm f/1.8 EX DG Asperical RF Reviews

I've used this lens for photographing concerts for about two years.

It's currently the widest lens with such a bright aperture, and for this reason alone, I couldn't part with it as most of my pictures are taken in very low-light conditions.

At f/1.8, images are very soft and I would recommend never opening the lens wider thn f/2 unless you want this effect. As you stop down the quality gradually improves, at f/2.8 it is very difficult to tell pictures taken with this lens apart from those taken with my Nikon 50mm f/1.4.

The build quality is good, although it did spend a month in the repair shop after the mount separated from the rest of the lens after I dropped it.

AF is very fast, as as it is done by rear-focusing, the legth of the lens does not change.

If you need a wide-fast lens, nothing else will do the job as well as this.

I would add a few things to the review initially posted by "inventory":

* close focus: this lens can focus as close as 20mm measured from the film (or sensor) plane. This means that you can almost *touch* your subject with the lenses' front element - which allows playing with extreme perspectives as much as you could possible want;

* huge filters: remember that this lens uses 82 mm filters. At this diameter, if you need a polarizer it will be one of the most expensive you can find :-) Or a gradual. Or anything.

* good build quality, but expect some usage marks on the plastic. I have used this lens to shoot in rain, fog, in high altidude clouds, close to 0 Celsius... and never had a problem except internal condensation once (which dissapeared by itself in a couple of hours). I definitely don't encourage exposing the lens to such conditions, but from my experience it can stand it without optical problems but with the price of some inesthetic marks on the plastic.

* optical quality: used this lens both on film (Fuji Provia) and digital (EOS 20D) and performed well on both. Indeed soft while full opened, but between 2.8 and 11 the image quality is very good. Beyond 16 it starts to soften due to the difraction.

* AF is very fast indeed (thanks also to the f/1.8 aperture), despite the fact that lens doesn't have USM/HSM. On the other hand, focusing is just a bit noisy. It never bothered me, but if you plan to go stealth in quite places AND your camera is already quiet AND you want to use AF, perhaps you should consider an USM/HSM lens.

* this is a fix lens. Depending on what you are usually shooting, this could cost you a lot of time with lens changing. If you shoot very wide either almost all the time or very rare, I would highly recommend this lens for its quality and versatility. But if you shoot in between, then you should perhaps consider a wide angle zoom to avoid frequently changing lenses.