AVI is like WAV, but that doesn't mean it's an exact image. AVI and WAV are both wrapper formats which can contain data encoded in any number of ways. WAV is usually uncompressed, and therefore exact, but AVI's are almost always lossily compressed. The sheer amount of data for an uncompressed video stream is such that only high end professionals tend to use it. It adds up to about 20Mb per second for full resolution. That's about 120Gb for a movie.
I'm not aware of a lossless video codec since the compression would be fairly minimal. If your video is coming off VHS, I wouldn't worry too much about lesslessness(?) since the quality will be very bad to start with. DiVX at about 700kbits per second should give you as good quality as the VHS, particularly if you have the time to do 2 pass encoding.