Anamorphic lens flare
A long horizontal, often blue streak extending from a bright light, associated with widescreen anamorphic lenses.
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What it is
An anamorphic lens flare is a long horizontal streak centered on a bright light. Anamorphic cinema lenses squeeze the image in one axis, so internal reflections that would look round through a spherical lens can spread into a line. Many coatings tint the streak blue.
Panavision C-series lenses and J.J. Abrams's Star Trek are common reference points. In post-processing, isolate the hottest highlights, blur them strongly along the horizontal axis, tint the pass, and add it back.
Gotcha: the streak must originate from an actual bright point and stay horizontal in screen space. A line drawn across every light, or one brighter than the source, looks pasted on and can wipe out faces or text.
Ask AI for it
Add an anamorphic lens flare from the brightest light only: extract a tight highlight mask, stretch it with a strong horizontal Gaussian blur, tint the streak cool blue, and composite it additively at low strength. Keep the line thin, screen-horizontal, and centered on the source.