Aerial imaging basics

Summary¶

Aerial imaging from a multirotor requires managing three compounding sources of image degradation: platform vibration (causing jello effect), exposure settings (rolling shutter artefacts at high shutter speeds), and pilot technique (jerky inputs producing unusable footage). The solution to each is distinct: vibration is controlled mechanically and by floating motor mounts; exposure is managed with neutral density (ND) filters and the 180° shutter rule; technique is developed through deliberate practice of smooth, planned movements. libdrone's HDZero Freestyle V2 system is optimised for low latency rather than imaging quality — for serious mapping and survey applications, a dedicated camera payload on the GX12 interface provides higher-quality results.

Concept¶

Jello effect and its mechanical cause¶

The jello effect is the wobbly, gelatin-like distortion visible in video from a vibrating drone. It is caused by the rolling shutter: the camera sensor reads pixel rows sequentially from top to bottom, not all at once. Each row is captured at a slightly different moment in time. If the camera is vibrating during the readout, successive rows are captured with the camera at slightly different positions, producing the characteristic lateral distortion.

The amplitude of jello is proportional to the vibration amplitude at the camera mount. Mechanical vibration isolation — floating motor mounts, correct O-ring durometer, balanced propellers — reduces vibration at its source. A well-built libdrone with balanced props and functional O-rings produces significantly less jello than one with worn mounts or unbalanced propellers.

A gimbal eliminates jello entirely by mechanically stabilising the camera in all three axes, regardless of airframe attitude. Without a gimbal, any pitch, roll, or yaw movement of the drone appears directly in the image.

Exposure: the 180° shutter rule¶

In still photography, fast shutter speed freezes motion — desirable. In video, frozen motion looks unnatural. Natural-looking motion blur requires a shutter speed approximately twice the frame rate: for 30 fps video, 1/60 s; for 60 fps, 1/120 s. This is the "180° shutter rule" (from the analogy to film camera shutter arc angle).

In bright daylight, achieving 1/60 s shutter speed requires reducing incoming light. A neutral density (ND) filter attaches to the camera lens and reduces light by a fixed factor (ND4 = 2 stops, ND8 = 3 stops, ND16 = 4 stops). The correct ND strength depends on ambient light conditions.

Additionally, slower shutter speeds reduce rolling shutter artefacts from residual vibration — the longer exposure time averages out the vibration rather than sampling it in the middle of a movement.

For the HDZero system: fixed-lens cameras have no filter thread. External filter holders or UV-cut filter kits are available for common HDZero camera models.

Composition and pilot technique¶

Aerial footage benefits from:

• Deliberate, planned movements: ascending reveal, orbit around a subject, linear tracking shot, fly-through. Each movement should be planned before execution — not improvised mid-flight.
• Slow, smooth inputs: stick movements should be gradual and continuous. Any sudden change in direction produces a visible jerk in the footage.
• Consistent altitude: altitude variation during a planned shot produces distracting vertical drift. Engage GPS position hold for altitude stability on survey and mapping passes.
• Golden hour shooting: the first and last hour of daylight produces warm, directional light with long shadows that add depth to aerial imagery. Flat midday light produces less visually interesting results.

Reference¶

ND filter selection guide¶

Values are approximate — measure exposure in the actual conditions.

Jello severity indicators and fixes¶

Procedure¶

Pre-flight imaging check¶

1. Balance all props on a magnetic balancer before imaging flights.
2. Verify floating mount O-ring condition (not cracked or flattened).
3. Fit ND filter appropriate to planned lighting conditions.
4. In Betaflight: enable GPS position hold for altitude stability during passes.
5. Review one flight's footage immediately after the first pass. Assess jello level and exposure before committing to a full session.

Rationale¶

Why imaging quality is secondary in libdrone's standard FPV system¶

The HDZero Freestyle V2 is selected for minimum latency for pilot safety and flight quality assessment — not for cinematographic quality. Its fixed lens, narrow FOV, and compression artefacts are acceptable for FPV navigation but not for mapping or documentation purposes. Applications requiring imaging quality should use a dedicated camera payload on the GX12 interface (e.g. Insta360 on Connector B GPIO2 camera trigger, or a survey camera with USB/UART control).

Connections¶

requires: - floating-motor-mounts - vibration-isolation-theory related: - jello-effect-mitigation - survey-imaging - thermal-imaging-payload leads_to: - jello-effect-mitigation - survey-imaging