Teaching a Foam Wing to Sign the Dusk
The blue hour arrived like a permissions slip. Thirty minutes, maybe forty if I’m generous with the definition, to fly a foam wing in the fading light and photograph whatever it leaves behind.
I’d been thinking about this since Choir Pitch Lightpainting a few days ago, where I watched the choir vanish while the baton’s light stayed visible. Long exposures eat dark objects and preserve bright ones. The singers disappeared; the colour trail remained. Tonight’s question: what if the moving light had wings?
Gilbreths, Picasso, and a Foam Aircraft
Light painting has a strange family tree. In 1914, Frank and Lillian Gilbreth attached small bulbs to factory workers’ hands and photographed the motions to eliminate inefficiency. Industrial time-motion study. Decades later, in 1949, Gjon Mili showed Picasso photographs of ice skaters with lights on their blades, and Picasso immediately grabbed a penlight and drew a centaur in the dark. The resulting images became famous. I’m not comparing my foam wing to Picasso’s hand, but I am borrowing his trick: the light moves, the camera waits, and the path becomes the artefact.
The LED strip runs on WS2812B pixels — individually addressable, which means I can program colour and brightness per pixel. Each one can pull up to 60 mA at full white, but I’m running them at about 40% brightness. The reason is photographic, not aesthetic: a bright LED becomes a fat smear on the sensor, losing the thin stroke I want. A dimmer LED writes a cleaner line. I add a 470-ohm resistor on the data pin and a 1000 µF capacitor across power to keep the signal stable, because nothing ruins calligraphy faster than a glitch.
The foam wing itself is familiar. Same aircraft I flew for APRS Skytrace Sculptures, minus the tracker. Tonight the payload is just the LED strip, a small microcontroller, and a LiPo cell that’s been giving me suspicious looks since the temperature dropped below minus ten.
What the Camera Wants
Dusk photography has rules, and the most annoying one is that autofocus fails when you attach a neutral-density filter. The ND filter lets me extend the exposure in marginal light, but it also blinds the camera’s focusing system. So I compose and focus without it, lock to manual focus, then screw on the filter like a darkroom door. Mess up the sequence and every frame comes back soft.
I set the camera to f/8, ISO 200, and a 25-second exposure. The field is frozen solid, the tripod legs are sinking into the snow, and the sky has that ozone-blue tint photographers call l’heure bleue. The colour comes from Chappuis absorption — ozone filtering out the red wavelengths after sunset — which is a more interesting fact than anyone standing in a cold field needs.
The flight plan is drawn on graph paper: a simple cursive loop, the kind of stroke a pilot’s wrist makes when signing a logbook. I’ve practised it in the simulator, which sounds ridiculous until you realize the camera will record every hesitation. A jerky turn becomes a visible stutter. A smooth arc reads as confidence. I’m not flying for the joy of flight; I’m flying for the photograph’s opinion of my control inputs.
The First Frame That Worked
The first three exposures are garbage. One starts late and catches only the recovery arc. One has the LED too bright — a neon smear that looks like someone dropped a highlighter. The third is fine except I flew the pattern backwards relative to the camera, which makes the stroke read like a signature written in a mirror.
Frame four is the one. The shutter opens, I launch, the wing traces the loop, I cut the LED at the apex, and the camera closes. When I check the preview, the stroke floats against a deep blue field, thin and deliberate. The aircraft isn’t visible — it was dark, it moved, it vanished — but the path remains. A cursive mark in the air, now frozen on a sensor.
The odd thing is that it looks like handwriting. Not mine, exactly, but someone’s. The wobble where I corrected for a gust. The slight thickening where I banked too slowly. The tail of the stroke where I held the turn a beat too long. It’s a signature that records not just the shape but the making of the shape.
What I Learned (Reluctantly)
WS2812B strips have a refresh rate around 400 Hz, which means the LED is actually blinking hundreds of times per second. At short exposures or fast movement, you can see the individual pulses as gaps in the line. At 25 seconds with a slow foam wing, it integrates smoothly. But if I ever try this with a faster aircraft, I’ll need to account for the strobing effect.
Also: cold batteries lie. The LiPo said 80% on the bench. After ten minutes in the snow, it said 40% and the LED strip started flickering. I should have kept a spare in my jacket pocket. I didn’t.
The field is dark now. Civil twilight ended six minutes ago, which means I’m technically in the window where Transport Canada wants anti-collision strobes on anything airborne. I pack up. The foam wing goes back in its case. The camera goes in the bag with the single good frame.
Back inside, I pull the image onto the laptop. The stroke glows against the blue. It doesn’t say anything yet — just a loop, a breath, a line drawn with a machine that doesn’t know it’s a pen. But it’s proof of concept. Tomorrow I want to try a word.