Q: “I’ve noticed on some CD’s I recently burned that there are these weird looking rings at various points (on the burned side) that look like shadows or something. I haven’t observed this on other discs in the past. They seem to play okay. Is this an indicator of a problem?”
A: We have to remember that the compact disc (and CDR) is a CLV (Constant Linear Velocity) medium. This means that the disc rotates at different speeds depending upon where on the disc material is being read or written. These speed changes are incremental – in other words they don’t all necessarily happen gradually or linearly across the disc – and do vary from one drive to another, and may vary with different media. At each increment where the rotational velocity speeds up (as the writing progresses from the inner to outer areas) the dye layer in the disc can get burned less deeply than the area before, which can sometimes result in visible rings. Different hardware and different media all behave a little differently, and while this phenomenon is always taking place it is a little unusual to be able to see well defined rings, but it’s not really indicative of a problem with the media or the burner. If the discs play fine, they are fine.