If the video appears very dark when playing back on a camcorder with an LCD, then attempt to increase the brightness level of the screen. Otherwise, reset the camcorder to factory specifications.
IMPORTANT: If the above steps do not resolve the issue, then the video may have been recorded that way. This could possibly be due to inadequate lighting conditions or low exposure value settings at the time of the recording. Connect the camcorder to a TV and view the tape to see if this may be the case.
NOTE: If the issue is still not resolved, then service may be required. Begin the procedure to send your Sony product into a Sony facility to be repaired.