Comparison of Canon EF 16-35mm ƒ/4L IS USM and Sigma 20-40mm f/2.8 EX DG Aspherical

Attribute	Canon EF 16-35mm ƒ/4L IS USM ×	Sigma 20-40mm f/2.8 EX DG Aspherical ×
Notes	Image Stabilization (up to four stop correction); Dust and moisture resistant; Includes lens hood, soft pouch.	Available AF Mounts: Sigma, Canon, Nikon, Minolta, Pentax
Magnification Ratio (x)	0.23	0.22
Filter Size (mm)	77	82
Length (mm)	112.8	107.8
Closest Focus (m)	0.28	0.27
Diagonal Angle of View (degree)	63.00 - 108.20	56.80 - 94.50
Focus Details	Inner focusing; full-time manual focus and USM	Internal with Dual Focus mechanism
Focal Length (mm)	16.00 - 35.00	20.00 - 40.00
APS Equivalent	26 - 56mm	1.5x: 30 - 60mm; 1.6x: 32 - 64mm
Brand	Canon	Sigma
Image Circle	35mm	35mm
Name	Canon EF 16-35mm ƒ/4L IS USM	Sigma 20-40mm f/2.8 EX DG Aspherical
Weight (g)	615	595
Type	Wide Zoom	Wide Zoom
Aperture (f)	4.00 - 22.00	2.80 - 22.00
Diaphragm Blades	9	8
Diaphragm Blades Type	circular	-
Lens Construction	16 elements in 12 groups, including 3 aspherical and 2 UD elements, fluorine coating	17 elements in 13 groups, including 2 aspherical elements
Zoom System	Rotary	Rotary
Diameter (mm)	82.6	89