Duo, Duo 2, Duo 3

Important.  Controls the quality of the clear (aka "high") and fluent (aka "low") resolution video.  More details...

You can ignore this. Use this feature if some devices such as TV screens and lights are flickering. Set to 60Hz for USA.

Optional.  Controls whether the camera automatically switches between color video and black & white video.

• If you're not sure or don't want to think about it, keep the default which is "Auto".

• If your area is well lit at night or you already have motion sensitive lights, you can probably set this to "Color" so the video is color all day and all night.

• If your area is not well lit at night, leave this set to "Auto" so it will automatically switch between color &black and white, depending on the amount of ambient light.  When set to "Auto",  if you also have the Spotlight set to "Auto", (Settings > Advanced) the night-time picture will probably start as black & white and then change to color a second or two after the spotlight turns on.

• I've never had a reason to set this to Black & White.

Optional.  Like the brightness setting on a TV.  Affects the entire  screen  the same amount for both day and night.
I've never had a reason to change the default setting (middle / 50%) on a Duo camera.  I prefer to use the newer "Brightness & Shadows" feature listed below.

Optional.  Controls where the camera name is displayed on the video.  Since the name is always white lettering, it is best to select a location that is relatively dark during the day and night (usually the bottom of the screen).

Optional.  Controls where the date/time is displayed on the video.  Since the date/time is always white lettering, it is best to select a location that is relatively dark during the day and night (usually the bottom of the screen).

Optional.  Controls whether a semi-transparent Reolink logo is displayed on the video.
I turn this off to be sure it won't cover something important.

Important but Optional.  Use this to create blackout areas on the video where ever there should be privacy.

• Create blackout areas for neighbors windows, doors, etc. to ensure you are respecting their privacy.

• There is no way for you or anyone else to see what has been recorded within a blackout area. 

• Please, either create sensible blackout areas or confirm your neighbors don't care.

Optional. Controls whether both cameras use the same automatic brightness level or whether each camera can automatically adjust to different brightness levels.
I've never had a reason to change this from the default value which is "on" (syncronize).

Optional. Manual controls for when there are both bright light and dark shadows at the same time.  More details...