The terms “Active and Passive refer to the kind of 2D glasses needed to view images in 3D on 3D TV sets. When 3D TV came on the market in 2010 TV sets were using active technology whilst passive technology came on the scene in 2011.

To see a 3D image in a flat 2D screen the human eyes have to be shown slightly different images to fool the brain into seeing depth. This is achieved by wearing glasses that do this (though not needed for the smaller screens of Nintendo 3DS). Active (shutter) glasses consist of small LCD screens that dim the left and then right “lenses” successively. This is controlled by an infrared signal emitted by the TV so each eye can then see the correct image. Active glasses are made of complicated electronics and are pretty expensive, and run on batteries and do tend to be heavy. On the other hand Passive Glasses are most like a pair of specially made polarised sunglasses. However, they differ from sunglasses (which are designed to block light to both eyes in the same was) in that polarised 3D glasses differentially block different kinds of light fractions from each eye. This then creates the depth illusion. This set up means that expensive electronics in the glasses are not needed and the TV set does not need an infrared emitter to make them work. This is why the glasses are cheaper, and are often given free with the sets.

However, the glasses are not chosen separately – there are sets that work with passive technology and those that work with active. The viewing experience is different and individuals will need to try each kind to know which is best for them.