Deep POV (or close third) collapses the distance between narrator and character by cutting filter words — 'she saw,' 'he felt,' 'she noticed' — and rendering perception directly. Instead of 'She felt afraid,' deep POV writes the fear as the character would experience it: 'The hallway stretched too long. Something was wrong.'
The effect is immersion: the reader stops noticing a narrator at all. It pairs naturally with free indirect discourse, where the character's idiom bleeds into the narration itself.
Filtered: 'She heard footsteps and realized she was not alone.' Deep POV: 'Footsteps. She wasn't alone.'
See also: Fix passive voice in fiction