It doesn't, unless the camera is damaged. How the blur looks is a consequence of the lens' optical design.

I would assume the fingerprint would be extremely sensitive to alignment and positioning of the optical elements, and I don't find it far fetched that those could shift minutely during the lifetime of a device without getting to a point where the camera is actually damaged.

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jagged-chisel 2 days ago | parent [-]

Only if adhesives allow such movement

	▲	ndriscoll a day ago \| parent \| next [-]
		Thermal expansion was a consideration when I took an optomechanical design course 15 years ago, for example (we had to memorize expansion coefficients of various common materials for quizzes, much to my annoyance). Like the glass itself changes size, altering how it focuses without even getting into the housing, which can also change size, shift around, vibrate, etc. Optical systems need pretty precise alignment.
	▲	zokier a day ago \| parent \| prev [-]
		No mounting is perfectly rigid and non-deformable.