Having a mismatch between the input signal range and the display & LUT's expected input range will cause image issues.
The graphs within ColourSpace will help defined when such configuration errors are causing problems.
Also see the Data vs Legal Levels page.
Signal Range
The expected signal range for any given display - TV Legal/Extended/Data Range - can also cause calibration errors, if the correct range workflow is not applied.
Errors can be within the signal path, including any TPG in use, or the display itself, or Patch Scale setting within ColourSpace.
In the Legal Display - Full Range Patches graph above the display has been profiled with a Data range signal, when the display expect a TV Legal range signal.
In the Full Range Display - Legal Patches graph the display has been profiled with a TV Legal range signal, when the display expect a Data range signal.
Comparing the two incorrect grey scale graphs it can be seen that when a display that expects a TV Legal range signal is profiled with a Data range signal, the grey scale is effectively compressed, with the lower (and potentially upper, depending on the display being Super White capable or not) areas showing repeated measurement values.
When a display that expects a Data range signal is profiled with a TV Legal range signal the grey scale is effectively stretched, with the lower and potentially upper areas being clipped, with the measured black being lifted, and peak white being reduced.
