Say I was watching a photon and an electron are racing (ignore other physics factors), the photon is moving away from the electron at a constant speed, v. Since the show plays too fast for me, so I slowed down the movie and re-watch the show again. In common sense, both electron and photon will be slowed down by equal proportional ratio respectively and the velocity v too. The result is photon moves away from electron but slower. For another case, electron is slowed down as before, but for photon it maybe just red-shifted instead of slowing down. The result is, velocity v increase and the photon moves faster away from the electron. Is there anything wrong?