Sigma Reviews

Sigma 20mm EX is an exceptionally well made lens. Performance is extremely satisfactory. It is almost indispensable for me to go without it when I am outdoors. Takes very good wide angle shots of buildings, parks and friends and family picnicking in the park. Shots have come very sharp and crisp with edge to edge brightness and sharpness. 20mm wide angle focal length gives you a very large depth of field which is essential for taking shots of wide open outdoors, filling your frame with a large expanse of ground/sky. Fast f1.8 aperture will let you take snaps indoors in natural light and hand-held shots of lighted buildings etc. in night time. Rear focusing feature of this lens results in fast AF and also the length of the lens remains same. Macro shots of subjects will give you convex mirror type of fascinating images and one can produce far more interesting effects depending on one's creativity.

Indoor flash photography may give rise to vignetting due to ultra wide nature of the lens as most flashes cover only 28mm span. This may probably be solved by using a wide angle attachment on the flash which to my disappointment was not available for my flash (Pentax AF-280T). Also 82mm filters may prove to be expensive. But I think a filter is essential for this lens as the front element glass is very near to the filter area.

All said this is an extremely satisfying buy (most bang for bucks) which gives you great results.

Performance:
This lens couldn't be much sharper at 15mm, it is pristine. Softer at 30mm, though still better than average corner to corner. I like that it seems optimized for 15mm. Very impressive, Sigma. Some flare, but any 15mm zoom is really prone to that. f3.5 is a little slow, but at 15mm 1/15 sec works for handholding, so it isn't a problem. Incredibly deep DOF at 15mm, makes for spectacular foregrounds, sharp from your feet to the horizon (at least with a cropping DSLR). 8 blades is very respectable for a lens of this price and not much is usually OOF.

Build:
Superior. Suprisingly light for it's size. Fast AF. The 82mm front thread is accomplished using a felt lined cap that slides firmly over the permanent pedal hood. A little awkward but it works a lot better than it sounds. No vignetting with an 82mm front filter using a cropping DSLR at 15mm, I doubt the same would be true with full frame where the angle of view is really uncanny.

Overall:
Arguably the best in its class, great price makes it even better. Everytime I see the images I thank myself for buying this lens.