Response time and refresh rate?
Q
I’m looking to buy a new, bigger monitor, mainly for writing. At the bottom of your reviews you list the main specifications, which include the refresh rate and response time. I think I understand what a refresh rate is, but what is the response time? Does it have any relationship to the refresh rate, or are they entirely different?
A
They’re certainly different, but it’s useful to understand the relationship between the refresh rate and the response time.
So, let’s start with refresh rate. This is perhaps the easiest specification to understand because it simply expresses how many times your monitor updates its on-screen image every second, measured in Hertz (Hz). The picture on a 75Hz screen, for example, updates (or refreshes) 75 times every second. The higher the refresh rate, the steadier the image. This is because faster refresh rates mean less visible screen flicker. Some of the fastest displays offer refresh rates of up 360Hz, although we question whether anyone can honestly tell the difference beyond about 75Hz. Plenty of gamers would no doubt disagree.
Response time is a measure of how quickly the individual pixels take to change from one colour to another, and is measured in milliseconds (ms). It’s important that a screen’s response time is lower than the time it takes to complete each refresh – otherwise pixels won’t change colour quickly enough and the resulting image may look blurry - see picture above. Each refresh of a 75Hz screen takes 13.33ms (that’s 1,000 divided by 75) to complete. So, for a 75Hz screen you’d want a response time lower than 13.33ms.
The key, then, is to ensure that any monitor you buy has a response time that’s lower – and preferably quite a lot lower – than the time it takes for each refresh. This generally isn’t a problem with 60Hz and 75Hz monitors, but as the refresh rate cranks up, so too does the need for an everlower response time.
Want to know the difference between technical terms? Email noproblem@ computeractive.co.uk
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