Strange blue dots on pictures taken from iPhone 15 Pro running iOS 18.3

This is possible due to a combination of factors:

1. Long Exposure in Night Mode: iPhones use long exposure in Night mode (up to 30 seconds) to gather as much light as possible. Even faint light sources, such as tiny cracks in doors, LEDs, or reflections, can become visible in the final image.
2. Light Leakage & Sensor Sensitivity: The iPhone's sensor is highly sensitive in low light. If there is even a minuscule amount of external light (from an LED indicator, power strip, or even gaps under doors), it may become amplified in the image.
3. Thermal & Sensor Noise: In complete darkness, long exposure can also introduce thermal noise, which may appear as faint colors or light spots in the image, even if no visible light is present.

Test in a True Darkroom

To confirm whether any light is seeping through cracks or if the sensor is introducing noise:

• Conduct the test in a fully controlled darkroom, such as a professional photography darkroom.
• Ensure no external LED sources (standby lights, power indicators, or hidden IR sensors) are active.
• Take multiple exposures to check for consistency.

If light still appears, it could indicate sensor noise rather than external light leakage.