The 10-20mm F4-5.6 EX DC HSM is Sigma's offering in the APS-C ultrawide zoom sector, first announced in February 2005. It was introduced amongst a flurry of announcements as manufacturers raced to provide wideangle zooms for the burgeoning APS-C format DSLR market, with similar offerings also appearing in short measure from the likes of Tamron and Tokina (not to mention all of the major camera companies). It has since become a very popular lens, due in no small part to offering the joint-widest angle of view of all the APS-C ultra-wide zooms, while being available in mounts to fit all of the major DSLR systems. Equally it's not hurt by having a very competitive price; it's notably much cheaper than the camera manufacturers' own offerings in this sector.

The optical formula features 14 elements in 10 groups, including three Super-low Dispersion glass elements for the minimization of chromatic aberrations, and three aspherical elements to reduce distortion and other aberrations. Users of Canon, Nikon, Sigma, and Four Thirds cameras benefit from an ultrasonic-type 'HyperSonic Motor' (HSM) for fast and silent autofocus, while the Pentax and Sony mount versions use the 'screw-drive' coupling from the camera body. The 'DC' designation indicates that this lens is designed for DSLRs with APS-C or smaller sensors, and isn't suitable for use on a full-frame body (the image circle isn't large enough, and vignetting will occur).

Of course the market doesn't stand still, and Tamron (arguably Sigma's biggest direct rival) has recently revised its own offering in this sector with the SP AF 10-24mm F3.5-4.5 Di-II LD Aspherical (IF). In the Four Thirds mount, Olympus has also entered the arena with its very impressive Zuiko Digital ED 9-18mm F4-5.6. And while Sigma has itself recently announced a new constant maximum aperture 10-20mm F3.5 EX DC HSM, the indications are that this will sell alongside the slower model as a higher-priced premium product. So how does the 10-20mm F4-5.6 stand up in the face of its new competitors?

Headline features

  • Ultra-wideangle zoom (15-30mm equivalent on 1.5x DX / APS-C DSLRs)
  • F4-5.6 maximum aperture
  • Available for Canon, Nikon, Sigma and Four Thirds mounts with built-in HSM focusing motor, and Pentax and Sony mounts with focus driven from camera body (non-HSM version)
  • For reduced frame (APS-C / DX / Four Thirds) format DSLRs only

Angle of view

The pictures below illustrate the focal length range (on Nikon DX format, 1.5x):

10mm (15mm equivalent) 20mm (30mm equivalent)

Sigma 10-20mm F4-5.6 EX DC HSM specifications

Street price • US: $440
• UK: £400
Date introduced February 2005
Maximum format size APS-C/DX
Focal length 10-20mm
35mm equivalent focal length • 15-30mm (1.5x DX)
• 16-32mm (1.6x APS-C)
• 17-34mm (1.7x Sigma SA)
• 20-40mm (2.0x Four Thirds)
Diagonal Angle of view (APS-C) 109º - 60º
Maximum aperture F4-5.6
Minimum aperture F22-32
Lens Construction • 14 elements/10 groups
• 3 SLD glass elements
• 2 hybrid aspherical elements
• 1 glass mold aspherical element
Number of diaphragm blades 6, rounded
Minimum focus 0.24m
Maximum magnification 0.15x
AF motor type • Ring-type Hypersonic Motor (Canon, Nikon, Sigma, Four Thirds)
• Full-time manual focus
Focus method Internal
Image stabilization None
Filter thread • 77mm
• Does not rotate on focus
Supplied accessories* • Front and rear caps
• Lens Hood
Weight 470 g (16.6 oz)
Dimensions 83.5 mm diameter x 81 mm length
(3.3 x 3.2 in)
Lens Mount Canon, Nikon, Pentax, Sigma, Sony, Four Thirds

* Supplied accessories may differ in each country or area