by one's lights

The story

Chiefly by the metaphor of lights as sources of illumination (e.g., lamps, lanterns, candles, torches) (thus, how something looks depends on the quality and quantity of the available light), but the sense of light as sightedness or vision is cognitively adjacent, setting up an interpretation of lights as referring to the eyes themselves (compare in my view); the potentially variable figurativeness behind punch someone's lights out is comparable here.