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Sigma AF 15-30mm F3.5-4.5 EX DG Lens Review (for Canon)
January, 2012 First things first. No, I did not switch over to Canon. I bought this lens used on eBay. The seller advertised it as a Nikon mount but it was for Canon (even though he said he used it on a Nikon D90). Luckily I was able to borrow a Canon camera before I resold it. The Sigma AF 15-30mm F3.5-4.5 EX DG lens was announced in July 2001 and made available in August. This is a full frame EX (Sigma pro grade) lens. When it was released it was one of the widest lenses available. The Nikon version has no built in motor so it won't autofocus with Nikon's lower end DSLRs (D40, D60, D3000, D5000, D3100, D5100). It's a DG lens which means it's ideal for Digital SLR use but is also suitable for film SLRs (for all of Sigma's letter designations see here). This is a solid built lens made of metal and plastic. The zoom and focus rings are rubber coated. The zoom ring turns smoothly. The lens has a clutch mechanism to switch between auto and manual focus, achieved by pulling the focus ring back and forth. You also have to move the AF/MF switch to manual as well. The lens mount is metal. The lens also has a distance scale and a slot for gelatin filters on the rear end. The front element is bulbous and protected by a built in petal hood. There are no filter threads on the front end, but the lens comes with a lens cap holder which can accept 82mm filters. But if you leave the holder on vignetting occurs at 15mm on a cropped sensor. With a full frame camera I would image vignetting occurs even further into the zoom range. Below you can see the extending front element along with the built in hood and the lens cap holder.
Sharpness in the center of the lens is very good throughout the zoom range wide open and improves when the lens is stopped down through f/8. Center sharpness is best at 15mm and f/8. Wide open the borders and corners are good. For the most part border and corner sharpness is consistent throughout the zoom range wide open through f/11. I would expect border and corner sharpness to be softer on a full frame camera. Barrel distortion is quite pronounced at 15mm. It improves further down the zoom range with almost no visible distortion by 30mm. Vignetting is most noticable at 15mm wide open. Stopping down a bit all but eliminates it. Chromatic aberration is visible at the wide end of the zoom but it should be easily correctable with in camera processing (if available), or post processing. Flare can be somewhat of a problem because of the protruding front element. At times I found the built in petal hood offered little protection from stray light, especially if the sun was in front of me. The Sigma AF 15-30mm F3.5-4.5 EX DG lens is now discontinued. Sigma has since released 12-24mm, 10-20mm, and 8-16mm wide angle lenses. I bought the 15-30mm looking for a wide angle lens with a little more reach. At the time I had been using the Sigma 10-20mm. Since I tested this lens on a Canon camera and not my familiar Nikon it was a little difficult to compare the two, but overall I felt the 10-20mm was sharper. It's also smaller and lighter. In addition, on a DX camera the 15-30mm isn't very wide. With a Nikon cropped sensor the effective field of view is 22.5mm. On a Canon sensor it's 24mm. With the exception of the flare issue the Sigma 15-30mm isn't a bad lens. When it was released there weren't many other wide angle options. But today there are many other choices, especially lenses made specifically for cameras with cropped sensors. Most of the newer lenses go wider, are better optically, and are also smaller and lighter. If you're looking for a wide angle lens and are on a very limited budget then the Sigma 15-30mm is worth taking a look at. Used copies sell for around $275. But if you have a few extra bucks it's worth getting one of the newer wide angle lenses. Specifications:
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