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Sigma 20mm F1.8 EX DG Aspherical RF Pentax KAF Review

Sigma 20mm F1.8 EX DG Aspherical RF

Main Features

  • 20mm Focal Range
  • F1.8 Max Aperture
  • Filter Thread: 82mm
  • Max Format: 35mm FF
  • Pentax KAF Mount
  • Weight: 520g.
  • Diameter: 89mm
  • Length: 90mm
  • Min Focus Distance:0.2m
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Sigma 20mm F1.8 EX DG RF Overview

Sigma 20mm F1.8 EX DG RF is a Fixed aperture Auto Focus (AF) Ultra-Wideangle Prime lens with 35mm FF max sensor coverage, and it is designed to be used with Pentax KAF mount cameras.

What type of photography is the Sigma 20mm F1.8 EX DG RF lens good for?

The type of photography that you are planning to use the Sigma 20mm F1.8 EX DG RF is an important decision factor. Here we have evaluated its suitability to various photography scenarios:

Photography Type Suitability
Bird/WildlifePoor
SportsPoor
PortraitFair
TravelAverage
StreetExcellent
WeddingFair
Walk AroundAverage
VloggingVery Good
LandscapeGood

Lenses in Pentax KAF Mount with Same Focal and Aperture Range
Model Coverage Weight Focusing Street Price
Samyang 20mm F1.8 ED AS UMC Lens Samyang 20mm F1.8 ED AS UMC
Compare
35mm FF 497gr MF Amazon B&H Photo

Reasons to Buy Sigma 20mm F1.8 EX DG Aspherical RF Lens

Here, we've included a summary of the advantages and disadvantages of the Sigma 20mm F1.8 EX DG Aspherical RF lens in a list form to help you determine whether it offers the features you need.

PROs
Autofocus
Aperture Ring
Distance Scale
DoF(Depth of Field) Scale
Hood supplied
Full-time Manual Focusing
Fast Aperture
Covers Full-Frame Sensor
9 Diaphragm Blades
Minimum focus distance of 0.2m / 7.9 inch
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Buy Sigma 20mm F1.8 EX DG RF from Amazon or B&H PHOTO


CONs

We couldn't find any significant Cons for Sigma 20mm F1.8 EX DG Aspherical RF


Lens Mount

Sigma 20mm F1.8 EX DG RF is compatible with cameras that have Pentax KAF lens mount. Some of the latest released cameras that are compatible with the Pentax KAF lenses are Pentax KF, Pentax K-3 III and Pentax K-1 II.

Sigma 20mm F1.8 EX DG RF is also available in Canon EF , Nikon F (DX), Sony Alpha and Sigma SA mounts.

Size, Weight and Filter Thread

Size and weight is a very important decision factor when searching for your next lens. Sigma 20mm F1.8 EX DG RF has a maximum diameter of 89mm and total length of 90mm. It weighs 520g / 18.3 oz.

Sigma 20mm F1.8 EX DG RF has a filter thread of 82mm.

Focal Range

Sigma 20mm F1.8 EX DG RF has a fixed focal length of 20mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 30mm.

Optical Image Stabilization

Sigma 20mm F1.8 EX DG RF doesn't have an optical image stabilization system so the only option to stabilize the image taken with this lens is to mount on a camera body with IBIS (sensor based In-body image stabilization).

Aperture

Sigma 20mm F1.8 EX DG RF has a max aperture of F1.8 and a minimum aperture of F22.0.

Optical Formula

Sigma 20mm F1.8 EX DG RF's optical formula consists of 13 elements in 11 groups . Special elements used in this design is 2 aspherical elements.

Lens Hood

Sigma 20mm F1.8 EX DG RF comes with a removable petal shaped lens hood which is handy to reduce lens flare and glare in your photos.

Body Colour

Sigma 20mm F1.8 EX DG RF is available in Black color.

Popular Comparisons of Sigma 20mm F1.8 EX DG RF

Here is the eight most popular comparisons of Sigma 20mm F1.8 EX DG RF amongst Camera Decision readers.

Top Alternatives of Sigma 20mm F1.8 EX DG RF Lens
Model Coverage Weight Focusing Street Price
Samyang 24mm f1.4 ED AS UMC Lens Samyang 24mm f1.4 ED AS UMC
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35mm FF 580gr MF Amazon B&H Photo
HD Pentax DA 21mm F3.2 AL Limited Lens HD Pentax DA 21mm F3.2 AL Limited
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APS-C / DX 134gr AF Amazon B&H Photo
Pentax smc DA 21mm F3.2 AL Limited Lens Pentax smc DA 21mm F3.2 AL Limited
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APS-C / DX 140gr AF Amazon B&H Photo
Voigtlander 20mm F3.5 Color Skopar SL II Lens Voigtlander 20mm F3.5 Color Skopar SL II
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35mm FF 205gr MF Amazon B&H Photo
Samyang 20mm F1.8 ED AS UMC Lens Samyang 20mm F1.8 ED AS UMC
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35mm FF 497gr MF Amazon B&H Photo
Sigma 24mm F1.8 EX DG Aspherical Macro Lens Sigma 24mm F1.8 EX DG Aspherical Macro
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35mm FF 485gr AF Amazon B&H Photo
Samyang 16mm f2.0 ED AS UMC CS Lens Samyang 16mm f2.0 ED AS UMC CS
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APS-C / DX 583gr MF Amazon B&H Photo
Carl Zeiss Distagon T 3,518 Lens Carl Zeiss Distagon T 3,518
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35mm FF 470gr MF Amazon B&H Photo

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**This post contains affiliate links and I will be compensated if you make a purchase after clicking through my links. As an Amazon Associate I earn from qualifying purchases.

Sigma 20mm F1.8 EX DG Aspherical RF Alternatives in Pentax KAF Mount
Model Coverage Weight Focusing Street Price
HD Pentax DA 21mm F3.2 AL Limited Lens HD Pentax DA 21mm F3.2 AL Limited
Compare
APS-C / DX 134gr AF Amazon B&H Photo
Pentax smc DA 21mm F3.2 AL Limited Lens Pentax smc DA 21mm F3.2 AL Limited
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APS-C / DX 140gr AF Amazon B&H Photo
Samyang 16mm f2.0 ED AS UMC CS Lens Samyang 16mm f2.0 ED AS UMC CS
Compare
APS-C / DX 583gr MF Amazon B&H Photo
Voigtlander 20mm F3.5 Color Skopar SL II Lens Voigtlander 20mm F3.5 Color Skopar SL II
Compare
35mm FF 205gr MF Amazon B&H Photo
Samyang 24mm f1.4 ED AS UMC Lens Samyang 24mm f1.4 ED AS UMC
Compare
35mm FF 580gr MF Amazon B&H Photo
Samyang T-S 24mm f3.5 ED AS UMC Lens Samyang T-S 24mm f3.5 ED AS UMC
Compare
35mm FF 680gr MF Amazon B&H Photo
Carl Zeiss Distagon T 2,821 Lens Carl Zeiss Distagon T 2,821
Compare
35mm FF 600gr MF Amazon B&H Photo
Carl Zeiss Distagon T 3,518 Lens Carl Zeiss Distagon T 3,518
Compare
35mm FF 470gr MF Amazon B&H Photo
Sigma 24mm F1.8 EX DG Aspherical Macro Lens Sigma 24mm F1.8 EX DG Aspherical Macro
Compare
35mm FF 485gr AF Amazon B&H Photo
Rokinon 24mm f1.4 Aspherical Lens Rokinon 24mm f1.4 Aspherical
Compare
35mm FF 580gr MF Amazon B&H Photo
Samyang 20mm F1.8 ED AS UMC Lens Samyang 20mm F1.8 ED AS UMC
Compare
35mm FF 497gr MF Amazon B&H Photo

Sigma 20mm F1.8 EX DG RF Detailed Specifications


General
Brand Sigma
Lens Type Prime
Lens Type Wideangle Prime
Lens Mount Pentax KAF
Max Format 35mm FF
Focal Range 20mm
Image Stabilization No
Colour Black
Zoom Method No Zoom
Power Zoom No Zoom
Zoom Lock No Zoom
Zoom Ratio 1.0X
APERTURE
Max Aperture F1.8
Min Aperture F22.0
Aperture Ring Yes
Diaphragm Blades 9
Optics
Optical Elements 13
Optical Groups 11
Special Elements 2 aspherical elements

FOCUSING
Min Focus Distance 0.2m
Max Magnification unknown
Autofocus Yes
AF Motor Type unknown
Full Time Manual Yes
Focus Method Rear
Distance Scale Yes
DoF Scale Yes
PHYSICAL SPECS
Weight 520g
Diameter 89mm
Length 90mm
Weather Sealing Unknown
Filter Thread 82mm
Filter Notes -
Hood Supplied Yes
Tripod Collar No
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Frequently Asked Questions about Sigma 20mm F1.8 EX DG Aspherical RF
is the Sigma 20mm F1.8 EX DG Aspherical RF a Weather Sealed lens?
What is the Minimum Focusing Distance of Sigma 20mm F1.8 EX DG Aspherical RF
is the Sigma 20mm F1.8 EX DG Aspherical RF an Autofocus (AF) lens?
What is the Filter Thread Size of Sigma 20mm F1.8 EX DG Aspherical RF
Does Sigma 20mm F1.8 EX DG Aspherical RF have Image Stabilization?
Does Sigma 20mm F1.8 EX DG Aspherical RF have Aperture Ring?
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