When a video signal is recorded, peak white levels can be usually be adjusted in a camera, a playback VTR or a number of intervening processing amplifiers. In some cases, natural tips of the video level can be overdriven by miscalibration and become clipped at the top of the video signal. Particularly bright scenes might have natural peaks above 100 IRE in raw camera footage, but clipped video signals above that range may mean detail in the video image is being lost during digitization. Video levels that are too high can also introduce noise into the image that is not in the original source.
Can it be fixed?
Yes, this is correctable through retransfer and adjustment of the VTR output using a processing amplifier to adjust video levels. Ideally the video will have natural peaks between 100 and 110 IRE, depending on the type of source footage (i.e., raw camera footage, off-air recording, or color-corrected broadcast air master).
High video level as seen in half-inch open reel video recording.
This waveform shows severe clipping
This waveform shows a corrected level