iPad 4 camera quality bad

So I took my iPad 4 into the apple store today to get a replacement for various reasons, one being the quality of the camera. I have for the past two years been doing both photos and videos with the iPad during the day and night times. I noticed the other night that the video quality had fallen. There is this strange noise affect across the picture and sometimes there would be moving lines going across too. Now I thought getting a new iPad this would have solved the problem, but I have the exact same problem. I just don't get it I never had this problem before till just the other day with my old iPad. I know that different lighting can affect the sensor on the camera lens, but I can't understand why this noise happens.