Sigma 20mm f/1.8 EX DG Aspherical RF

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 TypePrime Lens
Focal Length20mm
Mount TypeCanon EF, Nikon F, Pentax K, Sigma SA, Sony Alpha
FormatFull Frame / FX
Compatible Format(s)35mm Film / Full-Frame Digital Sensor Canon, Nikon (APS-C)
Compatible with TeleconvertersNo
Maximum Reproduction Ratio1:4
Optical Stabilization (Image Stabilization)No
Aperture Information
Aperture RingYes
Maximum Aperturef/1.8
Minimum Aperturef/22
Maximum Angle of View (Full Frame format)94.5°
Optical Information
Lens Elements13
Lens Groups11
Diaphragm Blades9
Aspherical Elements2
Nano CoatingNo
Super Multi-Layer CoatingNo
Focus Information
FocusAutofocus
Built-in Focus MotorYes
Hyper Sonic Motor (HSM)No
Rear FocusingYes
Minimum Focus Distance0.20m
Distance InformationYes
Filter Information
Filter Size82mm
Accepts Filter TypeScrew-on
Physical Characteristics
Weather / Dust SealingNo
Mount MaterialMetal
Tripod CollarNo
Dimensions8.89 x 8.64cm
Weight520g
Other Information
Available in ColorsBlack

Lens Construction

Sigma 20mm f/1.8 EX DG Aspherical RF diagram

MTF Chart

Sigma 20mm f/1.8 EX DG Aspherical RF chart

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