Here's a strip with a relatively new camera that I bought recently, developed by a party that I am using for the first time. Is this because of the camera not advancing the negative properly, or light leak, or is it because of bad job during the developing of the negatives? I got this on two rolls(out of ten). Actually, the other roll had the back 2/3 of the roll unexposed. Is this because of improper loading of the negative on my part or is there something wrong with the advancement function of the camera? The camera I was using is Nikon F4s. Thanks!