Photon counting

Photon counting means counting the number of tiny “particles” of light, called photons, that go in or out of a place. Photons are like the tiny bubbles in a glass of soda. You can count how many bubbles there are, and you can count how many photons there are too! Photons are too small and fast to count by hand, so we use special tools like cameras or machines to help us. When these special tools count photons, it’s called photon counting.