Sekonic SpeedMaster L-858D-U + RT-GX Transmitter Module Bundle Kit - DEMO

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SpeedMaster L-858D-U + RT-GX Transmitter Module Bundle Kit


With it’s 2.7” color touch screen and truly innovative and sophisticated features, the Sekonic Speedmaster L-858D-U leads the way to the next generation of light measurement control as the world’s first multi-function light meter for photographers and filmmakers. Leveraging over 60 years of experience in the image-making world with cutting-edge technology, the Sekonic Speedmaster L-858D-U has undergone a significant design change and boasts a comprehensive feature set sure to meet and exceed the demands of today’s photographers and filmmakers.
The first meter of its kind capable of measuring flash duration, while also being able to achieve an accurate ambient exposure reading in dimly lit scenes as low as 0.1 lx, the Sekonic L-858D-U provides image-makers of all levels with the critical exposure data they need to create stunning and beautiful imagery.
The first to provide wireless compatibility with Godox/Flashpoint products (Replacable with broncolor, Elinchrom, Phottix and PocketWizard transmitter sold as separately), the Sekonic Speedmaster L-858D-U also provides ultimate control to photographers seeking a faster and more streamlined workflow. Limitless creative possibilities are within reach through the meter’s ability to measure High Speed Sync (HSS) and calculate proper ambient-flash exposure for precision flash exposure control.
With an increased light-sensitivity and extended ISO and Shutter Speed Ranges, the Sekonic Speedmaster L-858D-U enables all image-makers to obtain measurements in extremely low light and turn those readings into creative decisions. Finally, matching the high-ISO capabilities of today’s cameras, by accurately metering in low-light, is finally possible."


Sekonic Transmitter Module RT-GX for L-858D-U Speedmaster light meter. Used to trigger Godox/Flashpoint enabled lighting and receivers.
Triggering and controlling the power level of Godox 2.4GHz wireless X system and Flashpoint 2.4GHz system built-in flash units
Modeling lamp output power control with ON/OFF
Wireless ID: (1 to 99 or OFF)
Channel: 32 (CH1 to 32)
Group: 16 (A to F, 0 to 9) + ALL
HSS (High Speed Synchro) flash radio triggering is available



Key Features

RT-GX Transmitter module for Godox/Flashpoint is built-in the meter
Incident Metering for Ambient & Flash
1° Spot Metering with Viewfinder
Measuring Range: -5 to 22.9 EV (ISO 100)
Illuminance Range: 0.1 to 2,000,000 lux
Extensive Range of Cine & Video Settings
HSS Flash & Flash Duration Measurements
Flash Analyzing Function; Extended Range
2.7" Touchscreen LCD; All-Weather Design

Retractable Lumisphere & 1° Spot

The Sekonic L-858D-U has a retractable lumisphere that enables you to measure both flat and 3 dimensional objects. The 1° spot is perfect for landscape photographers and measuring the contrast of any scene.

Measure Flash Duration

The first fully functional exposure meter to measure flash duration. Now know if your flash will freeze your subject.

Up to 3 Stops 
Increased Light Sensitivity

Accurately meter scenes lit by candlelight or
get the right measurement for long-exposure night photography.





RT-GX (built-in the meter)
Lens Cap
Soft Case
Start up guide
Anti-glare film
Safety Precaution
Limited 1-Year Warranty with 2-Year Extension upon Online Registration