The second postulate of SR is telling us that light always travels at C in a vacuum(absent of gravity) measured by any observer independent of the source or inertial frame the observer is measuring the light from. However, light is made up of photons which do not travel like ping pong balls in a straight line but are "moving" according to the laws of QM with all the weirdness like only being able to the probabilities of finding a photon at a certain volume of space. Yet, when we derive SR, we mapped the 2nd postulate into mathematics in such a way, which would be equivalent to some "special" ping pong balls being emitted from a source into all directions, always travelling at C into all directions, independent of the observer measuring them. The formulas we get for SR we derive from the two postulates are exactly the same as if we were to pretend that photons act like those special ping pong balls. Have there been attempts to map the second postulate of SR in a more precise way, such that it respects the full nature of light being made up of photons with their exact nature, as far as we know it according to QM, rather than treat them as special ping pong balls?