Like a camera, scanners need a certain amount of light to make a proper exposure. When you are scanning casino chips, a lot of the scan is going to be the background, the underside of the scanner lid, which is white. The white background reflects a lot of light back to the scanner, so the chips are generally underexposed. If you put something dark over the chips, I recommend a "Gray Card" which is available as a photo supply, the chips should come out brighter. The background should be contrasting (a different color than the chip) color and dark so that it is does not reflect too much light back to the scanner. The gray card is good for all but gray chips. For gray colored chips, use a black background over the chip. Does that make sense?