Long Range Searchlight

Case Study: Tactical Implications of Nighttime Illumination Enhancements in the Zenmuse Product Line

I. Introduction

Regardless of its Chinese origin, DJI's UAV technology and practical field experience remain highly instructive. The Zenmuse product line stands out as a dual-use solution, with capabilities clearly surpassing those required for civilian applications. This study analyzes two recent Zenmuse product releases, examining the underlying practical design considerations—particularly in response to operational feedback from the ongoing conflict in Eastern Europe. In May 2024, DJI launched the Zenmuse H30T, incorporating an infrared auxiliary illuminator into its existing high-sensitivity night vision and high-resolution thermal imaging system. Subsequently, in April 2025, the Zenmuse S1 was released, featuring a high-intensity spotlight module to support nighttime operations. This paper explores the rationale behind these design updates, particularly why active illumination was deemed necessary despite already possessing powerful passive sensors such as optical and thermal imagers.

【Illumination Range】For dual-use ISR payloads, drone-mounted cameras typically feature up to 30x optical zoom, with digital zoom extending practical working ranges to approximately 2 kilometers. While kilowatt-class xenon lamps can cover such distances, their size and power consumption exceed the capacity of small UAV platforms. Solid-state LED sources offer lower power draw and compact form factors but are generally limited to illumination ranges of up to 600 meters. Solid-state laser illuminators represent a newer solution capable of kilometer-scale coverage at low power and small size. In the case of the Zenmuse H30T, the infrared illuminator’s range is limited to ~100 meters—likely due to power constraints—while the larger Zenmuse S1 achieves up to 500 meters. Neither reaches the limits of current technology, suggesting trade-offs for power efficiency or other design considerations.

【Beam Angle Adjustment】 The beam angle affects the illuminated-to-shadowed area ratio within the camera’s field of view. Ideally, the illumination would match the camera's full FoV, but broader beams demand more power. Illumination strategies can be classified into three types:

1. Fixed beam angle, aligned with the most used FoV or targeting a specific zone—simpler mechanics reduce size, weight, and cost (e.g., the H30T design).
2. Variable beam angle, achieved by adjusting lens spacing within the illuminator for better integration with optical zoom—this adds complexity, weight, and cost.
3. Hybrid design, using multiple emitters with fixed but different beam angles, selectively activated to simulate variable coverage—mechanically simple but physically bulky due to the number of emitters (e.g., the S1 features a wide-angle and a narrow-beam module).

【Wavelength Selection】Dual-use systems typically employ either white light or near-infrared (NIR). White light offers color imagery with richer information but is visible to the naked eye, compromising stealth. NIR options, usually 850 nm or 940 nm, lie outside the visible spectrum. The 850 nm band may appear as a faint red glow at short range, while 940 nm is invisible to the naked eye, though both are detectable by night vision equipment. Notably, photon efficiency at 850 nm is roughly double that of 940 nm for standard optical sensors, making the former more energy-efficient. The H30T employs an 850 nm IR illuminator, while the S1 uses white light by default, though the latter could likely be adapted for IR emission with minimal modification based on user requirements.
Color infrared imaging—though traditionally monochrome—has emerged in recent years. While the Zenmuse H30T has yet to integrate this technology, interested readers may explore commercial color IR sensors online.

【Camera Exposure Modes】If the illuminated area matches the camera’s FoV, exposure is typically well-balanced. However, if the illuminated region occupies only a portion of the view, default matrix metering may lead to overexposure within the lit zone, obscuring critical details. Central-weighted or spot metering—assuming the illuminated region is centrally aligned—can significantly enhance image quality under such conditions.

III. Operational Needs and Field Feedback

Within the UAV industry, some argue that thermal imaging alone suffices for night operations. DJI's initial view aligned with this, as reflected in the H20T (launched in 2020), which featured thermal sensors but lacked night vision capabilities or IR illumination. The H20T had a maximum ISO of only 102,400 and no IR light source. What prompted DJI to change course by 2024? The answer likely lies in operational lessons from the Russia-Ukraine conflict.

Technological advancement alone does not explain the shift. As of 2024, mainstream DSLR cameras maxed out around ISO 50,000, and professional night surveillance cameras at ~ISO 100,000. Yet DJI’s H30T achieved an ISO of 819,200 and still added active IR lighting. Clearly, real-world needs—not spec evolution—drove these changes.

Thermal imaging specifications further support this conclusion. The H20T's thermal resolution (640×512) was competitive for its time, but the H30T doubled that to 1280×1024, surpassing top-tier offerings from FLIR and FLUKE, who still adhere to 640×480. DJI, not traditionally a thermal imager manufacturer, responded to strong user demand for higher resolution.

Operational reports from the battlefield highlight limitations of thermal technology: difficulty distinguishing friend from foe, inability to detect cold or unused weapons, and poor identification of cooled vehicles in forested environments. These issues rendered basic drone reconnaissance at night ineffective or prone to misinterpretation. Operators reportedly resorted to DIY IR sources to facilitate simplified IFF via hand gestures—feedback that likely influenced DJI’s product evolution.

The author simulated night conditions by photographing a cold, stationary tank in a forest at 200 meters using both thermal and low-light optical imaging. The thermal image failed to clearly identify the vehicle, while the passive optical sensor struggled with target classification—especially problematic given that both sides in the conflict use Russian equipment. With IR illumination, however, the tank’s shape and features became distinct, enabling confident identification. This simulation reinforces the battlefield feedback.

Thermal systems also cannot penetrate glass—preventing detection of vehicle occupants or hostile intent within—further limiting their utility. Emerging “thermal camouflage” techniques, such as insulated textiles or engineered thermal signatures, present additional challenges. These limitations underscore the importance of integrating optical night vision alongside thermal imaging.

In discussions with technical experts from major Japanese optics manufacturers, consensus emerged: each imaging modality has intrinsic advantages and shortcomings. A robust solution would integrate multiple sensor types—or even sensor fusion, as practiced by the U.S. military—combining optical and thermal feeds to ensure comprehensive coverage.

IV. Tactical Value of Extended Illumination Range

The preceding analysis outlines the reasoning behind DJI’s enhancement of night vision in the Zenmuse series. However, a critical limitation remains—range.

The H30T’s IR illuminator reaches only 100 meters; the S1 extends to 500 meters. These figures fall short of the 2-kilometer operational range typical for high-zoom optics. While DJI may have optimized for power efficiency, weight, or compactness, current technology suggests further improvement is feasible.

For example, the author's company developed the FA-1x1 series auxiliary illuminators for lightweight UAVs. Weighing ~300g (including internal battery), they reach 300–600 meters. A 1.5 kg enhanced version—powered via tether—achieves up to 1,200 meters. These specifications offer both longer range and greater discretion than DJI’s solutions.

V. Conclusion

The inclusion of an IR auxiliary illuminator in the H30T is not a routine upgrade, but a response to authentic operational requirements. Even within a multisensor architecture, active infrared lighting remains an indispensable component—providing tangible tactical benefits and contributing directly to mission success.