That is, they are not system adjustment errors but are picture quality degradations. Such degradations must be included in the picture quality assessment. Systematic adjustment errors that can be compensated by typical operational controls must be removed to insure meaningful picture quality assessment. These errors do result in degraded pictures hence the removal of such errors before subjective assessment must be reported as a system problem as part of the overall evaluation report. Adjustment of processed pictures It should be safe to assume signal parameters will be adjusted using a suitable test signal such as color bars in order to meet the viewing condition requirements.
Color bars are likely to be associated with the source sequence.
Therefore, the source sequence will be displayed in an optimum manner for the purpose at hand. It is possible, perhaps even likely, that the system under test has controls for adjusting gain and black level. If the processing were live, one would expect those parameters to be readjusted to their correct values prior to making the subjective assessment. In fact, if there were color bars at the start of the processed sequence it would be nearly impossible to keep a skilled television technician from making such adjustments. Alternately, if the processed sequence is recorded, there is still an opportunity to make such adjustments for playback and subjective assessment.