Comparison of Sigma 17-50mm ƒ/2.8 EX DC OS HSM and Tokina 16-50mm f/2.8 AT-X 165 AF PRO DX

Attribute	Tokina 16-50mm f/2.8 AT-X 165 AF PRO DX ×	Sigma 17-50mm ƒ/2.8 EX DC OS HSM ×
Notes	Available AF Mounts: Canon, Nikon; Included Accessories: Lens Hood	Image Stabilized (except for Pentax and Sony mounts). Available AF Mounts: Canon, Nikon, Pentax, Sigma, Sony. Included Accessories: Case, Petal-type
Magnification Ratio (x)	0.2	0.2
Filter Size (mm)	77	77
Length (mm)	97.4	91.8
Closest Focus (m)	0.3	0.28
Diagonal Angle of View (degree)	31.00 - 82.00	27.90 - 72.40
Focus Details	Internal with One-Touch Focus Clutch mechanism	Internal, with Hyper-Sonic Motor; AF/MF switch
Focal Length (mm)	16.00 - 50.00	17.00 - 50.00
APS Equivalent	1.5x: 24 - 75mm; 1.6x: 25.6 - 80mm	1.5x: 26 - 75mm; 1.6x: 27 - 80mm
Brand	Tokina	Sigma
Image Circle	APS-C	APS-C
Name	Tokina 16-50mm f/2.8 AT-X 165 AF PRO DX	Sigma 17-50mm ƒ/2.8 EX DC OS HSM
Weight (g)	610	565
Type	Standard Zoom	Standard Zoom
Aperture (f)	2.80 - 22.00	2.80 - 22.00
Diaphragm Blades	9	7
Diaphragm Blades Type	-	rounded
Lens Construction	15 elements in 12 groups, including 1 SD element	17 elements in 13 groups, including 2 FLD glass elements
Zoom System	Rotary	Rotary with lock
Diameter (mm)	84	83.5