Description
KR-S40: a compact manual strobe for underwater macro
The Kraken KR-S40 gives you 40 watt-seconds of flash power in a compact underwater strobe. It is a useful match for photographers who want to light small subjects without adding a large strobe to their rig. Five manual power levels let you choose the output yourself, with a rated 1.2-second recycle at full power.
Control the light on your subject
For nudibranchs, reef detail and other nearby subjects, the KR-S40 puts the emphasis on manageable size and repeatable manual settings. Turn the power dial to select 2, 5, 10, 20 or 40 Ws, then adjust output and position to suit your exposure.
The strobe provides coverage of over 60°. That makes it a practical starting point for macro, but it is a narrower beam than a dedicated wide-coverage strobe. If broad wide-angle scenes are your main subject, compare coverage and output across the strobe range rather than choosing solely for compact size.
Manual exposure, not TTL
The KR-S40 does not offer TTL automatic flash exposure. You set strobe power and camera exposure for the scene. That suits photographers who want direct control over their lighting and are comfortable adjusting it as subject distance and conditions change.
S1 and S2 optical slave modes let you configure triggering for your camera’s flash behaviour; Multi mode provides a separate repeated-flash option. Follow the manual to select the appropriate mode and test the complete camera, housing and fibre-optic connection before diving. A camera name alone does not establish compatibility: your housing and flash-trigger arrangement matter too.
Ready for the next frame
Full-power recycle is rated at 1.2 seconds, with approximately 500 full-power flashes per charge from the supplied 21700 battery. These are rated figures, not a promise that every battery or shooting sequence will perform identically. Plan charging around your actual use.
The built-in 300-lumen target light has a 15° beam to help you aim at small subjects. Its controls are separate from the flash-power dial. It is an aiming and focus aid, not a substitute for a video light.
Build the macro setup you want
The optional KR-SN08 optical snoot concentrates illumination for more selective macro lighting. The optional 4500K diffuser gives you a warmer light option. Both are sold separately.
For more output and broader coverage, compare the KR-S160. For a compact manual macro rig, the S40 keeps the choice straightforward: small size, five power levels and a clear path to snoot lighting.
Key specifications
- Flash power: 40 Ws maximum
- Manual levels: 2 / 5 / 10 / 20 / 40 Ws
- Trigger modes: S1, S2 and Multi; no TTL
- Full-power recycle: 1.2 seconds
- Full-power flashes: approximately 500 per charge
- Coverage: over 60°
- Colour temperature: 6000K
- Guide number: 16 at 1m, ISO 100
- Target light: 300 lumens, 15° beam
- Battery: one rechargeable 21700, 4000mAh, with USB-C charging
- Dimensions: 62 × 63 × 130mm
- Weight: 530g on land; 200g underwater
- Depth rating: 100m / 330ft
What is included?
KR-S40 strobe, 21700 battery, USB-C cable, white diffuser, ball mount, YS mount and spare O-rings. Camera, housing, tray, arms and fibre-optic cable are not listed among the included items.
Download the KR-S40 manual. For help choosing your camera’s lighting setup, browse our underwater photography and lighting guides.
