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Sirui 20mm T1.8 1.33x S35 AF Anamorphic Lens (FUJIFILM X, Blue Flares)

BH #SI20AF133XXB • MFR #20AF133X-XB
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Sirui 20mm T1.8 1.33x S35 AF Anamorphic Lens (FUJIFILM X, Blue Flares)
Key Features
  • 37mm Image Circle Covers S35 Sensors
  • Creates 2.35:1 Aspect Ratio in 16:9
  • Eye-Tracking Autofocus with STM Motor
  • T1.8-T22 Aperture
Combining the cinematic quality of 2.35:1 widescreen imagery with the convenience of subject-tracking autofocus, this Sirui 20mm T1.8 1.33x S35 AF Anamorphic Lens is a versatile, wide-angle lens designed specifically for FUJIFILM X-mount cameras with Super 35 sensors. With a 1.33x squeeze factor and T1.8 maximum aperture, the lens ensures exceptional low-light performance and allows for stunning subject isolation with its signature oval-shaped bokeh.
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Sirui 20mm T1.8 Anamorphic AF Overview

Combining the cinematic quality of 2.35:1 widescreen imagery with the convenience of subject-tracking autofocus, this Sirui 20mm T1.8 1.33x S35 AF Anamorphic Lens is a versatile, wide-angle lens designed specifically for FUJIFILM X-mount cameras with Super 35 sensors. With a 1.33x squeeze factor and T1.8 maximum aperture, the lens ensures exceptional low-light performance and allows for stunning subject isolation with its signature oval-shaped bokeh.

Powered by a precision STM stepping motor, the Sirui 20mm delivers smooth, accurate, and quiet autofocus—a rare feature in anamorphic lenses. With eye-tracking capability and buttons for both focus mode and autofocus lock, the lens provides complete creative control. A female USB-C port enables firmware updates, ensuring lasting performance. Compact and lightweight, the lens fits advanced technology and visual quality into a form factor ideal for handheld, gimbal, and run-and-gun shooting, making it a powerful tool for independent creators and professional productions.

Anamorphic Aesthetic
  • 1.33x squeeze factor for 2.35:1 images with a 16:9 sensor
  • Unique oval bokeh enhances subject separation and depth
  • Horizontal field of view equivalent to a 22mm full-frame lens
  • Blue lens flares for cinematic effect
Optical Performance
  • 37mm image circle covers Super 35 sensors or full-frame with vignette
  • T1.8 to T22 aperture for low-light performance and depth of field control
  • 15.7" minimum focus distance for close-up shots
  • Aspherical lens element minimizes chromatic aberration
Advanced Autofocus
  • STM stepping motor for smooth, silent autofocus
  • Eye-tracking autofocus for reliability during movement
  • AF/MF switch to toggle between autofocus and manual focus
  • AF-lock button to hold focus or recall custom focus settings
Practical Design
  • Uniform gear positioning with Sirui 40mm AF Anamorphic Lens
  • Compact (3.8" long) and lightweight (1.1 lb)
  • 360° focus throw with standard gearing
Versatile Compatibility
  • Compatible with FUJIFILM X-mount cameras
  • Standard 77mm front filter thread
  • Update lens firmware via female UCB-C port

Sirui 20mm T1.8 Anamorphic AF Specs

Key Specs
Focal Length
20mm
Maximum Aperture
T1.8
Lens Mount
FUJIFILM X
Lens Format Coverage
Super35/APS-C (37 mm Image Circle)
Filter Thread
77 mm x 0.75
Image Stabilization
No
Electronic Communication
Yes
Focal Length
20mm
Maximum Aperture
T1.8
Minimum Aperture
T22
Lens Mount
FUJIFILM X
Horizontal Squeeze (Anamorphic)
1.33x
Flare Color
Blue
Lens Format Coverage
Super35/APS-C (37 mm Image Circle)
Angle of View
Super 35
Horizontal: 85.6°
Vertical: 44.2°
Focus Scales
No
Optical Design
16 Elements in 12 Groups
Filter Thread
77 mm x 0.75
Minimum Focus Distance
1.3' / 0.4 m
Aperture/Iris Blades
11
Image Stabilization
No
Gear Standard
0.8 MOD
Gear Rotation
Focus: 360°
Electronic Communication
Yes
Camera Connection
USB-CFirmware
Diameter
Focus Ring: 3.4" / 86.4 mm
Iris Ring: 3.1" / 80 mm
Length
3.59" / 91.25 mm
Weight
1.1 lb / 488.4 g
Packaging Info
Package Weight
2.375 lb
Box Dimensions (LxWxH)
7 x 6.5 x 5.7"

Sirui 20mm T1.8 Anamorphic AF Reviews

Fun lens, great price

By Michael
Rated 5 out of 5
Date: 2026-01-10

Love the results of the Sirui 20mm, Anamorphic, Blue flare for MFT on my Lumix GH4. Hopefully, this lens will find a home on my next B&H Photo purchase- the LUMIX GH7!

Amazing lens

By Henry
Rated 5 out of 5
Date: 2025-08-11

Really a very practical lens and with the quality I expected

See any errors on this page?

Is there any vignetting if you combine this lens ...

Is there any vignetting if you combine this lens with the Sirui 1.25x adapter?
Asked by: Kieran
You may experience some vignetting when using the Sirui 20mm T1.8 1.33x S35 AF Anamorphic Lens (Nikon Z, Neutral Flares) with the Sirui 1.25x adapter.
Answered by: Boyd H
Date published: 2025-05-19

Constant 1.33 squeeze factor?

Constant 1.33 squeeze factor?
Asked by: john
Yes, the Sirui 20mm T1.8 1.33x S35 AF Anamorphic Lens (Micro Four Thirds, Neutral Flares) has a constant 1.33x squeeze factor.
Answered by: Paige K
Date published: 2025-10-16

Is this a focus by wire lens or will it work with ...

Is this a focus by wire lens or will it work with the DJI Focus Pro lidar?
Asked by: Timon
The Sirui 20mm T1.8 1.33x S35 AF Anamorphic Lens is a focus by wire lens but it is linear and can be used with the DJI Focus Pro LiDAR.
Answered by: John W
Date published: 2025-03-18

Is this lens compatible with the Sirui 1.25x ...

Is this lens compatible with the Sirui 1.25x anamorphic adapter?
Asked by: Kieran
Yes, the Sirui 20mm T1.8 1.33x S35 AF Anamorphic Lens (Nikon Z, Neutral Flares) is compatible with the Sirui 1.25x Anamorphic Adapter.
Answered by: Jonathan S
Date published: 2025-04-22

Is the squeeze factor constant?

Is the squeeze factor constant?
Asked by: john
Yes, the squeeze factor of the Sirui 20mm T1.8 1.33x S35 AF Anamorphic Lens (Micro Four Thirds, Blue Flares) is constant.
Answered by: Elliot A
Date published: 2026-04-13

Can this lens be used in full frame mode with ...

Can this lens be used in full frame mode with vignetting on Nikon bodies?
Asked by: Joshua
Yes, the Sirui 20mm T1.8 1.33x Anamorphic Lens can be mounted on full-frame Nikon Z bodies, with vignetting.
Answered by: Nick Y
Date published: 2025-11-11

Does this have a focus hold when using the AF?

Does this have a focus hold when using the AF?
Asked by: Sherman
Yes, the Sirui 20mm T1.8 1.33x S35 AF Anamorphic Lens (Sony E, Neutral Flares) does include a focus hold (AF-Lock) button.
Answered by: Chris H
Date published: 2025-06-20

This Leica L lens not compatible with Leica ...

This Leica L lens not compatible with Leica SL2-S? which Leica camera is compatible?
Asked by: Bill
Yes, the Sirui 20mm T1.8 1.33x S35 AF Anamorphic Lens (Leica L, Neutral Flares) is compatible with the Leica SL2-s camera. The camera will need to be set to release without a lens and manual or aperture priority exposure modes only.
Answered by: Dan W
Date published: 2025-12-04
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