What is the reason for doing a black trap or open port calibration
When the CE7000/A or Color i5 / Color i7 calibrates on the white ceramic tile, a top-end line (as close to 100% as possible) is established. To provide a bottom-end line (as close to 0% as possible), we perform a black calibrate. This, in effect, gives the unit two reference points and limits what the unit is capable of reading. A black calibrate will also help “filter-out” any low-end noise that may accompany darker colors.