Definition
A blurred halo or glow surrounding a bright spot of light on a display screen, photographic image, or instrument indicator, caused by light spreading or reflecting beyond its intended boundary.
Plain English
When a bright light source on a screen or photo bleeds outward into a fuzzy ring, making the edges look soft or glowing instead of sharp.
Context Anchor
Seen in aviation photography, aircraft inspection images, night-lighting discussions, and optical-display discussions when bright areas wash into nearby darker areas.
Derivation
From the Latin halo, meaning 'ring of light' (as around the sun or moon), with the suffix -ation meaning 'the process of.' So halation literally means 'the forming of a halo' — which is exactly what the effect looks like.
Why Pilots Care
Reduces clarity of runway lights, beacons, and instrument indications in low-visibility conditions.
Analogy
It is like taking a night photo of a bright streetlight and seeing a soft glow around the light instead of a sharp edge.
Intuition Check
Halation does not mean the object itself is glowing more. It means the image or view is adding a glow around a bright area.
Example Sentence 1
The pilot reduced the brightness on the radar display to cut down halation around the strongest weather returns.
Example Sentence 2
Panel lighting was adjusted to reduce halation that could distract from nearby instruments.