The cops receiver registers speed nearly instantaneously. The trick is that most of our detectors detect radar signals much further than the cop's receiver. That's because our detectors only have to detect the waves at half the distance as the cop's receiver does. The radar waves have to bounce off our vehicles and back to the cop's transmitter/receiver.I'm guessing ... his detector takes a few seconds to register your speed?
Think of it this way: you are one mile from the cop when he turns on his radar gun. Your detector has to detect the radar waves one mile away. The waves have to bounce off your SRT and go BACK to the cop, a total distance of 2 miles. Chances are, in most cases, by the time those waves travel that extra mile, they aren't a strong enough signal to register on his receiver. So, regardless of the power of the cop's radar gun, your detector always has twice the sensitivity of the cop's gun. (lots of variables here; sensitivity of your detector, the sensitivity of the radar gun, whether the cop is using 'instant-on', if there are no hills or curves between you and the radar gun, etc.)
Cameras cannot measure speed. Get a good detector; you'll be fine with it and you'll like it.I'd like a radar detector but I doubt I could react in time to slow down as the cnut in the camera van would have already recorded me speeding