It does looks like you don't have a 12V source on your camera, just 6.5V. If the camera blacks out and sometime you have kinda grayish color on your screen - you need to make sure that you have 12V source. The flow in both diodes is the same and they just make sure that the electricity flows in one direction. The reason why we have two power sources is because the aftermarket cameras are rated for 12V (in most cases); however, HU only gives 6.5V - which is not enough for AM camera and that is why your picture is not clear. HU's power is required to feel the camera and give the signal back to the HU that the camera is installed, the reverse bulb power source is a continuous power source for the camera's operation. That is why on the diagram the flow of both diodes is shown as from the power source to the camera.