Overdrive, also known as Response time compensation, reduces the monitor’s pixel transition time (or response time) to reduce ghosting of fast-moving objects by pumping more voltage to the pixels so they may transition faster. In simple words, overdrive helps sharpen objects when they are in motion, which results in a clearer picture.
Imagine playing a video game like Mario, in which your character is moving in the forward direction. If the speed of the character is increased further, you will see as if the character is leaving some shadow of it behind. This visible pixel transition seen by the human eye is what we call ghosting.
Why does ghosting happen?
To understand the reason behind ghosting, you need first to understand what response time is and what it has to do with the refresh rate.
The response time indicates how long a pixel takes to change from one color to another. It is measured in milliseconds. On the other hand, the refresh rate shows how long the monitor takes to display a new image.
For the sake of explanation of ghosting, let us consider that a monitor has a refresh rate of 75 Hz. It means that the monitor refreshes the image being displayed 75 times every second. This means there are 13.33 milliseconds between two cycles of refreshing the pixels. By refreshing an image, we mean that the display brings in a new frame every 13.33 milliseconds.
So for a monitor with a refresh rate of 75 Hz, every pixel should take 13.33 milliseconds to change. But if a pixel takes more than 13.33 milliseconds, the next frame would be there, but the “seemingly troubled pixel” will still be in its previous color, which results in trailing. There is not a problem with the pixel actually. The problem is that the display takes different times for the transition of different colors. The pixels in an LCD take a longer time to convert back from a specific color than to convert into that color.
So what we need here is that the pixels should convert back from their color before the frame cycle or the time of a frame ends, i.e., for a monitor having a refresh rate of 75 Hz, all the pixels should respond in a time smaller than 13.33 milliseconds. If they fail to do so, you get to see that frustrating trailing.
The same will be the case with any kind of moving object on the screen due to such pixels.
To help the pixels stay in the cycle bracket, monitors have this overdrive setting. Overdrive helps the pixels to transition from one color to another quickly.
Response time mentioned in the specifications is not usually the response time your monitor is set to. You have to make the changes and bring the response time to the required level.
As I mentioned above, the purpose of overdrive is to make the response time slower than the time monitor takes to refresh the frames. So the settings you need to make should be decided under the refresh rate of your monitor.
You should not set the overdrive too high or too low. Because if you set the overdrive too low, there will be ghosting. And, if you set the overdrive too high, you will confront an issue known as coronas. Coronas is inverse ghosting caused by an overshoot of the pixels as they change from their color too quickly that you start seeing a white trailing behind the moving object, which is equally disturbing. So, you need to make the response time symmetric, i.e., create a balance between both coronas and ghosting visibility.
Turn overdrive Enable or Disbale
Different monitors have different overdrive settings, and a more significant number of overdrive settings give you more control. Now let us see how you can make your monitor give you the desired display with this overdrive setting.
- Go to the ‘On-screen display’ menu.
- Look for the overdrive option: Different companies have different names for this setting but usually it is something like overdrive, Response time, or OD.
- Here, depending upon your model, you will see the options for overdrive as high, low, and normal and also turning it off completely. (As mentioned above, you can have a range of options depending upon the model of your monitor).
- Choose the option that suits your refresh rate.
Pixel response is usually a small fraction of the refresh rate, as often seen that 75 Hz monitors come with a 1ms response time, i.e., for a frame cycle period of 13.33 milliseconds, the response time is 1ms. But as mentioned above, the display may take different times for different colors, and you can still see ghosting or coronas effects.
The types of Response time: GtG and MPRT
Pixel response time can be described in 2 different ways, i.e., grey to grey and moving picture response time. And both are very different. Grey-to-Grey represents the time a pixel takes to change from one color to another, while the Motion Picture response time represents the time for which a pixel is visible. So, if you look at a pixel on a monitor with a frame time greater than its GtG response time, it stays there until the next refresh cycle while it might have gone through many of its Gray to grey transitions. We see that the monitor’s refresh rate limits the Motion picture response time. It is essential to know both the response times of a monitor because you will be in big trouble if the GtG response time is longer than the MPRT response time.