Comparison of Pentax 17-70mm ƒ/4 AL IF SDM SMC DA and Sigma 17-70mm ƒ/2.8-4 DC Macro OS HSM Contemporary

Attribute	Pentax 17-70mm ƒ/4 AL IF SDM SMC DA ×	Sigma 17-70mm ƒ/2.8-4 DC Macro OS HSM Contemporary ×
Aperture (f)	4.00 - 22.00	2.80 - 22.00
Filter Size (mm)	67	72
Notes	Included Accessories: Lens Hood	Image Stabilized (up to 4 stops); Available AF Mounts: Canon, Nikon, Sigma, Pentax, Sony; Accessory: lens hood LH780-03.
Closest Focus (m)	0.28	0.22
Magnification Ratio (x)	0.31	0.34
Diameter (mm)	75	79
Type	Standard Zoom	Standard Zoom
APS Equivalent	25.5 - 105mm	1.5x: 25.5 - 105mm; 1.6x: 27.2 - 112mm
Diaphragm Blades	7	7
Image Circle	APS-C	APS-C
Focal Length (mm)	17.00 - 70.00	17.00 - 70.00
Brand	Pentax	Sigma
Name	Pentax 17-70mm ƒ/4 AL IF SDM SMC DA	Sigma 17-70mm ƒ/2.8-4 DC Macro OS HSM Contemporary
Weight (g)	485	470
Diagonal Angle of View (degree)	23.00 - 79.00	22.90 - 79.70
Lens Construction	17 elements in 12 groups	16 elements in 14 groups, including FLD, SLD, and 3 aspherical elements
Zoom System	Rotary	Rotary with lock
Length (mm)	93.5	82
Diaphragm Blades Type	-	rounded
Focus Details	Internal; SDM with Quick-shift Focus System	Internal, with Hyper-Sonic Motor; AF/MF switch