What the bit depth controls
Grey scale is how many brightness levels each colour channel can produce. At 8-bit you get 256 levels per channel. At 14-bit you get 16,384. At 16-bit you get 65,536. The human eye can distinguish roughly 1,000 levels under good conditions, so why does anything above 14-bit matter?
Because of low-brightness content
The eye is very sensitive to banding in dark areas. A 14-bit panel showing a night sky allocates most of its levels to the bright end. In the shadows, two adjacent levels can be far enough apart to see a contour. A 16-bit panel has four times the resolution down there, so the gradient stays smooth.
The practical test
Play a black-to-white gradient at 20 percent brightness in a dark room, then walk from two metres to eight metres. At two metres you will see steps on almost anything. At eight metres a 16-bit panel still looks continuous while a 14-bit panel may show faint bands. If your content is mostly bright retail graphics, you will never see the difference.
Where it matters
- Stages and theatres with low-key lighting
- Museums and galleries showing photography
- Broadcast studios where the camera grades the signal
- Any wall showing HDR content
Where it is wasted money
A menu board, a lobby loop of bright product shots, a scoreboard. These are all high-key, high-saturation content. A 14-bit panel with good calibration will look identical, and the money is better spent on uniformity or a better processor.
One related number people ignore
Grey scale is only useful if the controller can carry it. A 16-bit panel fed by a controller that processes at 12-bit is a 12-bit system. Ask for the bit depth of the whole chain: source, processor, receiving card, driver IC. The weakest link sets the result.