RPi 2 dark picture after long runtime

    I installed a Rasperry Pi 2 in the home of my old parents, connected to a Samsung LCD TV (D-series). They don't use the Pi yet - I am still working to convience them that it is better than their old VHS recorder...

    Every few weeks I visit them, and when I turn the TV to the Pi input, I recognize that the picture is too dark with low contrast. But it is still not as dark as it would be with active power saving mode after some time of inactivity. The picture doesn't get bright again when I press keys. The device is not frozen, the OSD still reacts. The only thing that helps to bring back the normal bright picture is to reboot the Pi. Is this a known problem? How could I automatically make a nightly reboot via cronjob?

    Some TVs store unique picture settings for each framerate/resolution.

    What I mean by this is that I adjust the picture settings (on TV) to my preference when Kodi is outputting 1080p60. Now I play a movie and the Kodi output switches to 1080p24 ... all of a sudden the TV is using fresh picture settings. I must perform the adjustment once more. And also for 1080p30.

    And the picture settings can include HDMI black level.

    Perhaps this is not your issue, just a guess.