Why do I need to spend the extra money for a 240 Hz capable LED / LCD TV when I only have a 24, 30, or 60 Hz input?
Most broadcast signals max out at 60 Hz, and most high definition Blu-Ray signals are transmitted at 24 frames per second. So why would you want to buy an LCD / LED that can display ten times that? It turns out that the issue is more with the panel itself and the limitations of LCDs than the source.
LCD's are very prone to motion blurring, and it has to do with the technology of the liquid crystal display. If you set a 60 Hz LCD, a 120 Hz LCD, a 240 Hz LCD, and a plasma display next to one another, you will notice that there is a different visual appearance between the displays. It's hard to put your finger on exactly what the difference is, but it's hard to argue that the plasma screen doesn't look better.
Standard LCD's have traditionally displayed frames by sampling the stream at every refresh point and holding the pixels on screen for the duration of the frame. Then the image has to be altered for the next frame. For a 60 Hz update rate, each frame lasts 16ms. If the LCD was able to perfectly switch each liquid crystal between frames, there wouldn't be a problem; unfortunately, LCD's aren't so simple. The metric of how fast displays can effectively make the switch is known as motion-picture response-time metric (MPRT), and some displays are much better than others. Manufacturers put significantly better displays in their 240 Hz sets than in their 60 Hz sets.
Here's an article that does a nice job explaining why this effect can be found on LCD displays but not on plasmas or CRTs: Moving-Picture Response Time and Perceived Motion Blur on LCD Panels
Pay special attention to the diagrams on pg 13 and pg 15. They explain what causes the appearance of motion blur and how LCDs struggle to display motion effectively.
Here's a more scientific article that shows the same thing on the second page: Motion Blur Estimation on LCDs
In terms of actual use, there is a significant improvement from 60 Hz to 120 Hz, but the improvement with 240 Hz is less noticeable. This is why 480 Hz sets haven't become popular even though the technology is commercially available in TVs like the LG 55LM9600. That being said, I think the astute consumer can tell the difference between a 60 Hz, 120 or 240 Hz, and a plasma in terms of motion clarity with a standard HD signal.
In my guide to Samsung HDTVs, I rank refresh rates this way:
240 Hz Refresh Rate = Green – Good: Enhances Your Experience
120 Hz Refresh Rate = Yellow – Neutral: Won’t make a major difference
60 Hz Refresh Rate = Red – Bad: Below Average
Click Here to See the Rest of the Guide – The Best Samsung HDTV Comparison Chart and Feature Guide for LED and Plasma TVs
I differentiate between 120 Hz and 240 Hz in my ratings because of the 3D factor, something that should not be understated. Rather than a normal signal where motion is typically linear, or at least polynomial, 3D signals rapidly flash back and forth for both eyes. This requires a significantly improved response time. To take it to another extreme, Sony is developing TV's that can show two programs simultaneously on the same TV by flipping back and forth using active shutter 3D glasses and headphones. This really raises the bar for response time!
In order to effectively display clear motion in 3D movies, a 240 Hz television makes a difference.
In order to effectively display fast motion such as sports, you'll want at least a 120 Hz television.
A 60 Hz LCD is going to be much more prone to motion blur than the higher end displays. I would recommend staying away from these TVs.
