Comparison of Carl Zeiss 18mm f/3.5 Distagon T* 3.5/18 and Pentax SMC P-FA 31mm f/1.8 AL Limited

Attribute	Carl Zeiss 18mm f/3.5 Distagon T* 3.5/18 ×	Pentax SMC P-FA 31mm f/1.8 AL Limited ×
Brand	Carl-zeiss	Pentax
Name	Carl Zeiss 18mm f/3.5 Distagon T* 3.5/18	Pentax SMC P-FA 31mm f/1.8 AL Limited
Focal Length (mm)	18.00	31.00
Image Circle	35mm	35mm
Lens Construction	13 elements in 11 groups	9 elements in 7 groups, including 1 aspherical element
APS Equivalent	1.5x: 27mm	46.5mm
Closest Focus (m)	0.3	0.3
Length (mm)	84	68.5
Filter Size (mm)	82	58
Magnification Ratio (x)	0.083	0.16
Notes	Available SLR mounts: Canon EF (ZE), Nikon F (ZF, ZF.2), Pentax K (ZK). Lens shade included. Nikon ZF.2 version includes CPU interface for autoexposu	-
Aperture (f)	3.50 - 22.00	1.80 - 22.00
Diagonal Angle of View (degree)	99.00	70.00
Weight (g)	470	345
Focus Details	Manual focus only	-
Type	Wide Prime	Wide Prime
Diameter (mm)	87	65