Sigma 15-30mm f/3.5-4.5 EX DG lens

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The Sigma 15-30mm f/3.5-4.5 EX DG is a professional wide-angle lens made by the Sigma Corporation. The lens is produced in EF mount, SA mount, F mount, Minolta AF mount, and Pentax K mount varieties, all with the same optical formula. Although the lens is of the digital era and popular among APS-C digital SLRs (it was the first lens to allow a 24 mm field of view on a 1.6x cropped body), it is a full-frame lens.

The 15-30 has a petal-type lens hood built into the casing, which cannot be removed. While the lens comes with an adapter to mount screw-in filters (82 mm), these vignette on anything larger than a 1.5x cropped sensor. Drop-in gelatin filters can be used with full-frame digital SLRs or 35 mm film.

[edit] Specifications

Aperture range: f/3.5 to f/29
Minimum focus distance: 11.8 inches
Maximum magnification: 1:6
Angle of view: 110.5 to 71.6 Degrees (different for cropped cameras)
Groups/Elements: 13/17
Length: 5.1 inches
Diameter: 3.4 inches
Weight: 1.36 lbs

[edit] Use

The 15-30 EX is a "slow zoom," meaning the (variable) aperture is smaller than would be needed for low-light, flashless photography. In addition, the autofocus motor is slow and somewhat noisy. For these reasons the lens is rarely used for wedding or event photography.

On the other hand, the "ultrawide" angle of view makes the lens especially well suited to landscape and architectural photography.