Subject: How does a proper time of zero for light square with waves?

Since proper time is measured relative to the difference between the velocity of
the observer and the observed, how is it that a wave phenomenon which depends on
a time element be applicable to light, which has a proper time of zero? Doesn't 
this preclude any motion whatsoever for light? And, without any motion, how is 
it that we measure light as wavelength? Is this just a convenient construct with 
historical roots and no applicability, or is there a mistake in my framing?

Re: How does a proper time of zero for light square with waves?