Walt H,
What you're describing would be more of an ambient light sensor, which is not a feature of the LN40A550. That would adjust the brighness and contrasted based on the light in the room.
The Energy Saving mode is set to reduce energy consumption when the unit is powered on. In it's dormant stage (off position), it consumes a very small amount of energy to retain the settings.
--HDTech
When Energy Saving Mode is set to "Auto", is this supposed to make adjustments acording to the lighting in the room i.e. higher for night viewing when it's dark and lower for daytime viewing?

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