Comparison of Pentax 17-70mm ƒ/4 AL IF SDM SMC DA and Sigma 28-70mm f/2.8 DG DN Contemporary

Attribute	Pentax 17-70mm ƒ/4 AL IF SDM SMC DA ×	Sigma 28-70mm f/2.8 DG DN Contemporary ×
Aperture (f)	4.00 - 22.00	2.80 - 22.00
Filter Size (mm)	67	67
Notes	Included Accessories: Lens Hood	Available AF Mounts: L-Mount, E-Mount; Dust- and splash-proof at lens mount
Closest Focus (m)	0.28	0.19
Magnification Ratio (x)	0.31	4.6
Diameter (mm)	75	72.2
Type	Standard Zoom	Standard Zoom
APS Equivalent	25.5 - 105mm	42 - 105mm
Diaphragm Blades	7	9
Image Circle	APS-C	35mm
Focal Length (mm)	17.00 - 70.00	28.00 - 70.00
Brand	Pentax	Sigma
Name	Pentax 17-70mm ƒ/4 AL IF SDM SMC DA	Sigma 28-70mm f/2.8 DG DN Contemporary
Weight (g)	485	470
Diagonal Angle of View (degree)	23.00 - 79.00	34.30 - 75.40
Lens Construction	17 elements in 12 groups	16 elements in 12 groups, including 2 FLD, 2 SLD and 3 aspherical elements; Super Multi-Layer Coating, Nano Porous Coating.
Zoom System	Rotary	Rotary
Length (mm)	93.5	101.5
Diaphragm Blades Type	-	rounded
Focus Details	Internal; SDM with Quick-shift Focus System	Internal focus with stepping motor; AF/MF switch; Supports DMF, AF+MF on Sony cameras