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Sea&Sea Sony Alpha Universal Housing Compatible with a7R Mark V
By DPG Editorial Staff, May 31, 2023 @ 01:00 AM (EST)

Sea&Sea has now added the Sony a7R Mark V to the list of cameras compatible with its universal housing, unveiled in July 2022. The MDX-αU already supported the “entry-level” a7 Mark IV, “video-centric” a7S Mark III, “pro sports” a9 Mark II, “8K-capable” a1, and the high-resolution predecessor, the a7R Mark IV. As a result of the “universal” design, initial mounting of the camera is a little more involved, there are some functional limitations that require workarounds, and an optional additional kit is needed.

The universal housing features a large acrylic back panel, which reduces weight and aims to provide better visibility of the LCD. There’s a fiber-optic cable cover, which is designed to protect the connectors and prevent them from falling out. A leak alarm unit is included as standard equipment. The housing is available in a silver finish as well as the tradtional black.

The MDX-αU supports fiber-optic connectivity with compatible Sea&Sea YS strobes in TTL or manual modes via the optional Optical YS Converter S2 or Manual Flash Trigger, respectively. If you trigger your YS strobes via sync cords, you also have the option of an electrical connection.

Available from retailers such as Backscatter, the MDX-αU is priced at $4,400.

When purchasing underwater photography equipment like the products mentioned in this article, please support DPG by supporting our retail partner—Backscatter.com.


Sea&Sea MDX-αU Underwater Housing for Sony α1/α9II/α7sIII/α7RIV/α7IV/α7RV
Universal compatibility with Sony Alpha series. The future-oriented mirrorless SLR compatible housing is now fully loaded


Universal design for the future. The back panel is designed to be large

The back acrylic panel is more than twice as large as before to improve visibility of the monitor and reduce the underwater weight. Furthermore, it is a sustainable design that can be used with new cameras in the future with minimal parts replacement.

Newly designed fiber-optic cable cover Newly designed optical fiber cable cover

Newly designed fiber-optic cable cover included. Prevents optical cable terminals from falling out and smartly protects light-emitting panels and cable terminals. Includes a strap to prevent loss of the cover.

Leak Alarm Unit as standard equipment

The Leak Alarm Unit, which was previously available as an option, is now included as standard equipment. It is effective not only for early detection of underwater flooding accidents, but also for protection of equipment by checking its waterproof performance before entry. CR2032 lithium battery included.

Product No.44135 Leak Alarm Unit Product Page.

Strobe Synchro System

Three optional strobe connection methods are available.

1. Optical TTL connection
[Product No.50151]  Optical YS Converter S2

Compatible with SEA&SEA “Optical YS Converter S2” which converts the strobe light emission signal of the camera to LED light and synchronizes with the SEA&SEA YS strobe. It is a high-performance converter that does not just emit simple light-emitting signals, but also performs TTL auto light control.
*Sony original adapter “ADP-MAA” is required separately for connecting camera and optical YS converter.

Optical TTL connection

2. Optical manual connection
[Product No.50146]  Manual flash trigger

For those who do not need TTL photography, the fiber-optic cable connection enables manual firing of the YS strobe.

Optical manual connection

3. Electrical connection
[Product No.50147]  Strobe connector/N
[Product No.50122]  Optional Sync Cord 2-pin Connector

YS strobes can be electrically connected with a sync cord.

Electrical connection

Full range of standard equipment

  • Grip Plus made of silicone material
  • Robust yet secure fit to hold the housing in place
  • Lighting can be deployed as desired from the SA8 fixed ball base
  • Pre-equipped with lanyard hooks for convenient transportation

Focus Point Movement Settings

To perform "focus point operation" during shooting, please make a custom setting for the focus point in the dial customization of the camera in advance. The focus point can be moved by operating the front/rear dial.

The following is a guide to the setup procedure for assigning the focus point operation to the front and rear dials.


Enhancement Customization Kit

Common to all models

  • Up/down/left/right buttons on the multi selector cannot be used
  • Use the up/down/left/right buttons on the control wheel instead
  • The up/down/left/right buttons on the control wheel cannot be used to move the focus point
  • Focus point can be moved with the front and rear dials using the camera’s dial customization function

α1/α9II camera

  • Drive mode/focus mode dials are not available as standard
  • It can be supported by using the optional kit
  • If you want to change the drive mode etc. without modification, you can temporarily use it by registering the camera’s custom shooting setting in advance and calling up the function, but it is not a perfect substitute

α7IV camera

  • The shooting mode lever cannot be used
  • This can be handled by using an optional kit
  • S&Q cannot be used

α7V camera

  • The shooting mode lever cannot be used
  • This can be handled by using an optional kit
  • S&Q cannot be used

[Product No.50148] α1 customize kit for MDX-αU
Compatible with drive mode dial/focus mode switching lever.

[Product No.50149] α9II Customize Kit for MDX-αU
Compatible with drive mode dial and focus mode selection lever.

[Product No.50150] α7IV Customize Kit for MDX-αU
Compatible with shooting mode selection lever.

[Product No.50152] α7RV Customize Kit for MDX-α7RVU
Compatible with shooting mode selection lever.
*The α7RV customize kit cannot be used with an electrically connected strobe sync system.

Other Features

  • The Port Lock prevents the port from turning or loosening and the Port Lock lever is specifically located to avoid being unlocked accidentally
  • The housing is equipped with a lens-lock release button which makes it possible to change lenses easily, without opening the housing
  • Pulling out the Focus/Zoom Dial gives sufficient room inside the housing to easily accommodate larger diameter lenses
  • Equipped with the Optical Viewfinder 0.5x as standard. Other optional viewfinders such as the VF180 1.2x, VF45 1.2x and Optical Viewfinder 0.66x, 0.8x can be used
    ※Some vignetting occurs.When the VF180 1.2x is mounted on housing, the uper part of the camera's viewfinder cannot be viewed due to vignetting
  • Equipped with two sacrificial zinc diodes (one on the front case and the other on the rear) to prevent electrolysis damage
  • Tripod screw mount is located on the centre underside of the housing


[Construction] Body: corrosion-resistant aluminum alloy (machined)
  Grip: corrosion-resistant die-cast aluminum alloy
[Depth rating] 100m / 330ft
[Dimensions (WxHxD)] 330 x 169 x 137 mm / 12.9 x 6.6 x  5.4 inches
[Weight] Approx. 2,900g / 102.3oz (Housing only)
[Set Item] Silicone grease, O-ring remover, Hex wrench (6mm / for grip dismounting), Hex wrench (4mm / for Lanyard bolt), Hex wrench (2mm), O-ring maintenance manual, Instruction manual (this manual), CR2032 lithium battery (for leak alarm unit), Leak alarm unit manual pump
[Attached accessories to the product] Housing body cap, Fiber-optic cable cover




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