Comparison of Pentax 17-70mm ƒ/4 AL IF SDM SMC DA and Tamron SP AF 28-75mm f/2.8 XR Di LD Aspherical IF

Attribute	Pentax 17-70mm ƒ/4 AL IF SDM SMC DA ×	Tamron SP AF 28-75mm f/2.8 XR Di LD Aspherical IF ×
Filter Size (mm)	67	67
Notes	Included Accessories: Lens Hood	Available mounts: Canon, Minolta-D, Nikon-D, Pentax; Includes petal type lens hood.
Closest Focus (m)	0.28	0.33
Magnification Ratio (x)	0.31	0.26
Type	Standard Zoom	Standard Zoom
Length (mm)	93.5	92
APS Equivalent	25.5 - 105mm	1.5x: 42 - 112.5mm; 1.6x: 44.8 - 120mm
Zoom System	Rotary	Rotary, telescoping
Image Circle	APS-C	Image Circle
Focal Length (mm)	17.00 - 70.00	28.00 - 75.00
Brand	Pentax	Tamron
Name	Pentax 17-70mm ƒ/4 AL IF SDM SMC DA	Tamron SP AF 28-75mm f/2.8 XR Di LD Aspherical IF
Weight (g)	485	510
Aperture (f)	4.00 - 22.00	2.80 - 32.00
Diaphragm Blades	7	7
Diagonal Angle of View (degree)	23.00 - 79.00	32.00 - 75.00
Lens Construction	17 elements in 12 groups	16 elements in 14 groups, including one Extra Refractive Index element, four Aspherical elements and three Low Dispersion elements
Diameter (mm)	75	73
Focus Details	Internal; SDM with Quick-shift Focus System	Internal