Comparison of Pentax 20-40mm ƒ/2.8-4 ED Limited DC WR HD DA and Sigma 18-50mm f/3.5-5.6 DC

Attribute	Pentax 20-40mm ƒ/2.8-4 ED Limited DC WR HD DA ×	Sigma 18-50mm f/3.5-5.6 DC ×
Filter Size (mm)	55	58
Notes	HD coating, SP (Super Protect) coating; Weather-resistant construction	Available AF Mounts: Canon, Nikon, Minolta/Sony, Pentax, Four-Thirds, Sigma; HSM version available for Nikon mount
Closest Focus (m)	0.28	0.25
Magnification Ratio (x)	0.2	0.29
Diameter (mm)	71	62
Type	Standard Zoom	Standard Zoom
APS Equivalent	30.5 - 61.5mm	1.5x: 27 - 75mm; 1.6x: 28.8 - 80mm
Diagonal Angle of View (degree)	39.00 - 70.00	27.90 - 69.30
Image Circle	APS-C	Image Circle
Focal Length (mm)	20.00 - 40.00	18.00 - 50.00
Brand	Pentax	Sigma
Name	Pentax 20-40mm ƒ/2.8-4 ED Limited DC WR HD DA	Sigma 18-50mm f/3.5-5.6 DC
Weight (g)	283	250
Aperture (f)	2.80 - 32.00	3.50 - 22.00
Diaphragm Blades	9	7
Diaphragm Blades Type	rounded	-
Lens Construction	9 elements in 8 groups, including 1 ED and 1 SLD element	8 elements in 8 groups
Zoom System	Rotary	Rotary
Length (mm)	68.5	67.5
Front Element Rotation	-	-
Focus Details	Quick-shift Focus; DC focus motor	Internal; HSM version available for Nikon mount