Response Time

Response time is the time a screen pixel needs to change from one colour or shade to another. It is given in milliseconds, and a smaller number means a faster change.

How it works

Every pixel changes colour as the picture moves. If the change is slow, a faint trail stays behind moving objects. This smear is called ghosting. Makers usually quote grey-to-grey time, written GtG, which is the time to move between two shades of grey. Common quoted values are 1, 4 and 5 milliseconds.

What the numbers mean

• The figure is often the best case for one shade change, not an average across all of them.
• Many makers quote it with a speed-up setting called overdrive switched to its strongest level. That setting can push pixels past the target shade and leave bright or dark halos, called overshoot.
• OLED pixels switch in a fraction of a millisecond, while LCD types such as IPS and VA are slower.

What it does not promise

Response time is not refresh rate, which is how often the picture updates, and it is not input lag, which is the delay between a signal and the picture. A low figure does not mean there will be no blur, because motion blur also depends on refresh rate and how the eye follows movement. There is no single test method, so figures from different makers are not strictly comparable.