Lens Summary
Brand: Sigma
Also Known As: Sigma 20mm f/1.8 EX DG RF
Lens Type: Prime Lens
Format: Full Frame / FX
Focus: Autofocus
Lens Mount: Canon EF, Nikon F, Pentax K, Sigma SA, Sony Alpha
Release Date: 2008-01-01
MSRP Price: $629
Made in: Japan
Infrared Rating: Good
Production Status: In Production
Lens Description: The Sigma 20mm f/1.8 D EX DG Aspherical Lens has a clutch-like system for switch between AF and MF modes. The system is very similar to the Sigma 105mm f/2.8 EX macro lens I reviewed previously. You push the manual focus ring forward to disengage the focus ring for auto-focusing. For manual focusing, you pull it toward you to engage the clutch. When the ring is set to AF, you can rotate the focusing ring all you want, you won\'t change the focus on the lens. When the lens is auto-focusing, it also doesn\'t effect the position of the manual-focusing ring. The manual focus ring is wide so there is no chance that you\'ll miss it in operation.
Sigma 20mm f/1.8 EX DG Aspherical RF Specifications
| Lens Specifications | |
|---|---|
| Lens Type | Prime Lens |
| Focal Length | 20mm |
| Mount Type | Canon EF, Nikon F, Pentax K, Sigma SA, Sony Alpha |
| Format | Full Frame / FX |
| Compatible Format(s) | 35mm Film / Full-Frame Digital Sensor Canon, Nikon (APS-C) |
| Compatible with Teleconverters | No |
| Maximum Reproduction Ratio | 1:4 |
| Optical Stabilization (Image Stabilization) | No |
| Aperture Information | |
| Aperture Ring | Yes |
| Maximim Aperture | f/1.8 |
| Minimum Aperture | f/22 |
| Maximum Angle of View (Full frame or larger format) | 94.5° |
| Optical Information | |
| Lens Elements | 13 |
| Lens Groups | 11 |
| Diaphragm Blades | 9 |
| Aspherical Elements | 2 |
| Focus Information | |
| Focus | Autofocus |
| Built-in Focus Motor | Yes |
| Rear Focusing | Yes |
| Minimum Focus Distance | 0.20m |
| Distance Information | Yes |
| Filter Information | |
| Filter Size | 82mm |
| Accepts Filter Type | Screw-on |
| Physical Characteristics | |
| Weather / Dust Sealing | No |
| Mount Material | Metal |
| Dimensions | 8.89 x 8.64cm |
| Weight | 520g |
| Other Information | |
| Available in Colors | Black |
Lens Construction
MTF Chart
