How Your Phone Sees in the Dark

In near darkness, your phone takes a photo brighter than what your own eyes can see.

There is barely any light, so how does night mode pull a bright photo out of the dark?

When you tap the shutter, your phone does not take one photo. It quietly captures a burst, often a dozen or more, over a couple of seconds. Each dark frame is full of random speckles called noise. But here is the trick: the real scene stays the same in every frame, while the noise is different each time. Software aligns the frames, correcting for your hand shake, then averages them together. The constant scene reinforces itself, and the random noise cancels out.

Because the noise is random, averaging many frames shrinks it by the square root of their number. Stack nine frames and the grain roughly drops to a third, revealing a clean, bright image.

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