When you venture to purchase an LED TV, the first aspect you concentrate on is the picture quality. This is where you start looking at the specifications while comparing two or more TVs. The thumb rule for companies marketing electronics is that “higher the number, the more preferable it is”.
Are we correct in assuming this fact? It is a surprise that we are not entirely right in deducing this fact.
There are other factors involved such as colour accuracy and contrast ratio affecting the picture quality to the normal eye. One such important factor is the ‘Refresh Rate concept’.
What is the refresh rate in LED televisions?
In very simple terms, this specification refers to the number of times per second that a video screen is updated. The concept of refresh rate has its origins in the last century with the invention of the movie projectors.
These projectors hit 24 frames per second (expresses as frequency in Hertz or Hz). Hence, you find Standard Definition TV sets with refresh rate of 60 Hz in the US and 50Hz elsewhere in the world. This entails that these TVs refresh 60 frames and 50 frames in a second depending on the refresh rate.
Let us simplify things a bit more
When you have a TV with a refresh rate of 60 Hz it necessarily entails that the TV refreshes or changes the images 60 times in a second. Thus one image remains on the screen for a total time of 1/60th of a second. Modern TVs have the technology to increase the rate to 120 Hz (120 frames per second) or even 240 Hz in the case of the 1080p HD TVs.
Some TV manufacturers market their TVs as having a refresh rate of 480 Hz, 600 Hz, or even 960 Hz. Is this true? It can surprise you that this is purely a marketing gimmick. The least expensive of present-day 4K TVs have a refresh rate of 60 Hz or at best 120 Hz.
It is very rare that a TV goes beyond 240 Hz. These companies use certain additional technologies to take care of the motion blur. Check out Cnet’s Post about Refresh rates for in-depth details.
What is motion blur?
Each frame of a TV image is a stationary image. As the normal TV refreshes a frame 60 times in a second, you get a motion image. This implies that one frame remains for a period of 1/60th of a second before the next one takes over.
The motion blur is actually a creation of our brain. It assumes as to what the next image will be in the next fraction of a second.
The LCD and OLED TVs hold on to the frame for 1/60th of a second before refreshing it. Thus, your brain senses a blur at that split second when the frame refreshes. It is too minute to be noticed.
There are two common methods to overcome this motion blur, frame interpolation and black frame insertion. The present day TVs use these methods as a sort of a modifier. Thus you see companies using the term ‘TruMotion 120/240Hz or Image Motion 120/240Hz’ in their specifications. The refresh rate in such specifications is actually 60Hz/120Hz respectively. Also, checkout rtings guide 120hz vs 60hz.
These are technical points, but one should learn to read between the lines when you sit down to read the specifications before purchasing a 4K HD TV.