Halation is a diffused ring of light that often appears around small, bright highlight areas in a photograph. It occurs when light passes through the emulsion, reflects off the film base, and exposes the light-sensitive layer slightly out of alignment with the original image.
Halation can add a soft, glowing effect to images, but excessive halation may reduce sharpness and contrast. Understanding halation helps photographers control exposure, choose appropriate film, and manage lighting to achieve the desired visual effect.