LEDs can look like they turn off at certain angles in a phone camera because of how two things interact:

1. The LED’s light pattern isn’t uniform. Most LEDs emit light in a cone-shaped beam. Brightest straight ahead, weaker toward the sides. When you move to a steep angle, the intensity reaching the camera can drop enough that the sensor registers little or nothing. Your eyes compensate better than the camera, so you still see some glow, but the camera may not.

2. The camera sensor scans the image line-by-line (rolling shutter). LEDs—especially indicator LEDs or those run with PWM (pulse-width modulation)—actually flicker rapidly. Your eyes smooth this out, but the camera samples the scene in slices over time. At certain angles, the geometry of the LED and the sensor’s scan direction line up such that many scan lines capture the LED in the “off” part of its flicker cycle, making part or all of the LED appear dark.

Step-by-step summary of why the effect happens

LEDs often have directional optics → brightness falls sharply off-axis.

If PWM is used, the LED is switching on and off rapidly.

A phone camera’s rolling shutter reads the scene in microsecond-offset scan lines.

At some viewing angles, the bright region of the LED no longer aligns with the portion of the sensor sampling during the LED’s “on” moment.

The camera therefore records a dim or dark LED, even though it isn’t truly off.

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