There was discrepancy with the black level on the MCDUs in comparison to the displays of the PFD, ND and ECAM. The MCDU (converted to bypass AIRINC429 and 115 VAC requirements) uses a clear thick glass to give the effects of the CRT.

To match the black levels of all the aircraft displays, 20% dark smoke tint was installed onto the MCDUs giving them dynamic black levels, and realistic CRT simulation.