The thin blue squiggle in the image above is a Destabilized Sensor Reflection. A relatively new phenomenon in photography.
A sensor reflection in a phone camera occurs when light reflects off the sensor (the digital "film" of the camera), then back through the lens, off the flat glass covering the lens assembly, and then back down to the sensor to get recorded. These reflections appear diagonally opposite the light source in the image. It's essentially a type of lens flare, and frequently mistaken for a UFO.
Modern phones have amazing image stabilization.So if you take a long exposure, say 1-2 seconds, the phone will generally do a great job of taking a stable photo which normally would have come out a blurry mess. The above image is 1.1 seconds, but still looks pretty sharp.
Destabilized Sensor Reflections (DSRs) can also show up in video, particularly when zoomed in. The dancing dot here is a reflection of the green light in the pool, but it moves so erratically while the pool light is fairly steady and smooth, so it's hard to recognize.
Stabilization works by shifting the image. When you move the camera a little then everything in the image moves together in the opposite direction. So all the stabilization has to do is move it back the right amount. As you can see it does it really well. However, the sensor reflection moves in the opposite direction, so the stabilization actually makes things worse.
Here's an example with multiple lights where I deliberately rotated the camera to the right, but the image of the socks is perfectly clear.
Example of social media:
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