Comparison of Canon EF 20mm f/2.8 USM and Pentax SMC P-FA 31mm f/1.8 AL Limited [S]ave
| Attribute |  Canon EF 20mm f/2.8 USM × |  Pentax SMC P-FA 31mm f/1.8 AL Limited × |
|---|---|---|
| Brand | Canon | Pentax |
| Name | Canon EF 20mm f/2.8 USM | Pentax SMC P-FA 31mm f/1.8 AL Limited |
| Focal Length (mm) | 20.00 | 31.00 |
| Image Circle | 35mm | 35mm |
| Diaphragm Blades | 6 | - |
| APS Equivalent | 32mm | 46.5mm |
| Focus Details | Inner focusing; full-time manual focus and USM | - |
| Length (mm) | 77 | 68.5 |
| Magnification Ratio (x) | 0.14 | 0.16 |
| Closest Focus (m) | 0.25 | 0.3 |
| Filter Size (mm) | 72 | 58 |
| Aperture (f) | 2.80 - 22.00 | 1.80 - 22.00 |
| Diagonal Angle of View (degree) | 94.00 | 70.00 |
| Weight (g) | 405 | 345 |
| Lens Construction | 11 elements in 9 groups | 9 elements in 7 groups, including 1 aspherical element |
| Type | Wide Prime | Wide Prime |
| Diameter (mm) | 71 | 65 |
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