My postulate is this, that the velocity of light can only be gauged in the frame in which it was generated and that its apparent velocity in other frames in relative motion are illusory. The only frame which indicates the true behavior of light is the one which can be viewed by itself, with all others removed, and as if it is stationary, and the light will still be seen to exist. When any other relative frame is viewed in isolation, the light cannot exist because it has no source. You can't have a light beam existing by itself in space, therefore those other frames cannot be used to gauge the behavior of the light and do not require the true light frame to be adjusted to suit it by altering its time passage rate or physical dimensions
I do not believe that it is necessary to manipulate relative frames by modifying time and/or length to make it appear that light has the same velocity in all frames at the same time. I postulate that viewing a light beam in the frame in which is is generated from another frame in motion relative to it is like viewing a video recording of it on a portable player and moving the player around. The light beam's velocity is not really being sped up or slowed down by the motion of the video player, it is an illusion of sorts and therefore requires no correction. What say you of my postulate? Can you justify modifying the light generating frame to make it conform to a non generating frame so it appears to have the same velocity in both simultaneously?