- Ultra wide-angle zoom lens designed for Sigma digital SLR cameras
- 15-30mm focal length
- 3.5-4.5 maximum aperture
- Super Multi Coating reduces flare and ghosting that tends to occur when using digital SLR cameras
- 17 lens elements in 13 groups; aspherical elements at front and rear lens groups
Product Description
This rectilinear 15-30mm f3.5-4.5 EX Aspherical DG DF lens provides focal lengths from 15mm ultra-wide angle to 30mm wide-angle and is the first of its kind in the world.This lens has minimum focusing distance of 11.8 inches (30 cm) at all focal lengths with 110.5 degrees (wide) to 71.6 degrees (tele) of angle of view. (Maximum magnification is 1: 6.)It incorporates hybrid aspherical lens in the front lens group to minimize distortion and astigmatism, and molded glass aspherical lens in the rear lens group to minimize spherical aberration.This lens equipped with dual focus mechanism and also inner focusing system. It is easy to hold the lens, since the focusing ring does not rotate during auto focusing, and yet it provides adequate torque of the focusing ring during manual focusing the lens.This lens is desirable and for digital SLR cameras also. Its effective zoom range will be 22.5mm-45mm wide angle zoom lens on most SLR digital cameras.Sigma 15-30mm f3.5-4.5 EX Aspherical DG DF has a mechanical design which has six groups zoom system. This new mechanical design will minimize astigmatism for all focal lengths.This lens is equipped with a non-removable type lens hood (Petal-shaped) to prevent extraneous light harmful for image quality.This lens uses rear gelatin (insert type) filters. The iris diaphragm has 8 blades to obtain beautiful out focus of image in the foreground and background.
Douglas Henderson @ 3:52 pm
I bought a used 15-30mm EX lens on Ebay late last year and have been using it on an SD14. At the widest end (15mm and F11), image quality is simply splendid. Great contrast, color and resolution with a sharp image running right off either end of the frame with sharp corners. Depth of field is enormous at 15mm, even when just set to infinity, resolving sharp near-foreground and distant background elements together. There is a small amount of CA which seems to increase a little as you focus closer than infinity. There is some distortion, but this is not apparent in landscape shots.
Image resolution is very good at all focal lengths–but from 19mm through 30mm, the aperture needs to be stopped down to F14 to get the best corner resolution. Image distortion and CA diminish at longer focaL lengths.
The lens is big and so somewhat awkward, but surprisingly light for its size. Auto-focus with my copy is inconsistent (often focusing well past infinity), so I just put the lens in manual (a two step operation) and set infinity by hand. The bulging front lens element will produce flare in images if struck by sun or strong light. I keep the lens cap ring attached to the fixed lens hood, which greatly shields the lens and does not induce any corner light fall-off when used on an SD14, even at the widest 15mm setting. And I cup my hand beyond the hood to block light when shooting more toward the sun. This seems to work well. Any flare is usually visible in the camera viewfinder, so you can adjust what you can to block it before taking a picture. Lens flare is one of the major cautions for this lens in various reviews. In practice, I’ve had no trouble with flare, though keep the problem in mind.
It produces excellent images–the end results often showing far more to a scene than expected. F11 seems to be the ideal aperture for 15mm, but F8 works in a pinch in low light.
Addition 10/11/08: I’ve determined that the ideal infinity focus point with this 15-30mm lens varies with the focal length. I don’t trust the auto-focus still and manual focus everything. The lens focus ring set to its infinity mark works perfectly for landscape shots at 15mm. But for 20mm and 24mm, the focus ring should be turned inside the infinity mark about 1/16th inch or more. Corner resolution of images improves markedly doing this. At 30mm, the focus should be set just inside the infinity mark on the lens focus ring. Image results are even better now than my earlier review above. With considerable use now and nice results, I’d give this lens 5 stars.