Capture range is the volume in which the sensor can physically detect motion

What it is

Capture range is the volume in which the sensor can still, by physics, emit a signal for a hand or body: the lens field of view, the distance infrared illumination can reach, the usable time-of-flight depth range, the solid angle of a radar beam. Hardware and optics set it; it is not the “please operate here” box drawn in software. Inside that volume a hand can be tracked; outside it, the signal vanishes before any software rule runs.

Why it happens

Depth cameras are limited by baseline, resolution, and IR power: too close and they bloom or cannot focus; too far and the cloud thins; off the lens there are no pixels. Stereo vision goes “blind” early on weakly textured walls, so the nominal range is still quoted while effective capture has already collapsed. A millimeter-wave radar’s range is its antenna pattern; it can see through some occluders, but angular resolution is poor and finger-scale motion smears first at distance. Capture range is therefore a volume that warps with distance, angle, material, and lighting, not the cube in the datasheet. Datasheet range is a number on a laboratory reflector; real hands, dark clothing, and solar IR noise shorten the usable volume.

Studying it

With a calibrated tape or motion capture, move a hand (or a full body) along the optical axis and along the edges. Record the nearest, farthest, and lateral limits at which joints are still stably reported. Repeat in a bright room, in backlight, and with dark gloves, and plot the actual capture envelope against the spec. Dependent measures are consecutive tracked frames, keypoint jitter, and loss rate—not gesture-class accuracy. Classification has not started; range already decides whether there is input.

Where it stops holding

Inside-out headset tracking carries capture range with the head: large for the wearer’s own hands, almost nil for a third person at a desk. The ranging language of a desktop module does not transfer. A contact glove has no optical volume; talking about capture range is meaningless. Stitched multi-sensor setups create overlap bands and seams; signal in an overlap is not a unique reliable coordinate. A maximum distance measured at 25 °C on a specified reflectance is not a promise to gallery visitors.

Applying it

• Draw the measured capture envelope on the floor plan with tables, columns, windows, and traffic, rather than pasting a FOV glyph.
• Give installers a physical boundary for “a hand must appear here to be seen at all,” labeled separately from the later software interaction volume.
• Walk a hand along the optical axis and along the field edge at acceptance; the point where stable tracking dies is capture range. Do not write it down as an interaction-design parameter.

Related

• Same group: C4.20.2 The interaction volume is the subspace of capture range treated as valid input · C4.20.3 Motion inside capture range but outside the interaction volume is easily mistaken for system failure · C4.20.4 The interaction volume is typically smaller than capture range to leave a margin for tracking jitter
• Adjacent: C4.10 Sensing volume and interaction distance · C4.31 Lighting, occlusion, and environmental conditions
• Search: capture range · field of view · depth camera range