The rate that the eyes/brain cannot detect changes will depend on many things including size of objects and speed (and possibly smoothness) of motion. Using po

The rate that the eyes/brain cannot detect changes will depend on many things including size of objects and speed (and possibly smoothness) of motion. Using polarised 3D both eyes should still get 48fps they just receive different(ly polarised) light. TVs using active shutter glasses do reduce the frame rate by half but will usually be reducing it from 96Hz or more By the way - in the cinema at 24fps each frame is usually flashed twice which encourages the psycho-visual system to fill in the blanks and smooth out the motion so it appears sharper and less blurred than it would on a LCD/Plasma TV screen that usually holds the image for the duration of the frame. Some high end models can do black frame insertion if they are using the right type of LED backlighting and are set to the right mode.