OK. I took my camera out to the garage and took four pictures. The LEDs work, I guess, but don't help the image at all.
The first is of the backup camera, with the camera inactive and the LEDs off. You can see the array of 18 LEDs to the left and right of the camera lens.
The I turned the monitor system on and took another picture. This time the LEDs show up as purple dots which, I guess, means that they're on. The dots aren't very bright, but I'm not sure if that means anything.
Next, I took a pictures of the image on the backup monitor, first with the overhead garage lights on. Pardon the mess!
Finally, I took a picture of the monitor, with the overhead lights off...relying on the LEDs alone. (Well, you can see a little light in the upper left hand corner, the result, I think, of a little light leakage into the garage.) Anyway, as near as I can tell, the LEDs have no positive impact on the image.
All in all, it's a bit disappointing given that the system manual indicates the LEDs should be effective for a distance of 50 feet. (Note that I did play around a bit with brightness and contrast and the like, but that didn't seem to make any difference.)