Answer: SEPIA

Sepia refers to a reddish-brown color that is often associated with old-fashioned or vintage photographs. It is also commonly used to describe a nostalgic or aged quality. In the context of a "nostalgic filter," sepia typically refers to a filter or effect applied to photographs or images that gives them an appearance reminiscent of old, faded photographs, evoking a sense of nostalgia and warmth.

Note: The provided meaning of the answer is for the latest New York Times crossword puzzle clue: Nostalgic filter. Explanations are generated by AI and may be inaccurate.