Q: I still use my Panasonic TC-P42S30 plasma. I love how it reproduces movies from streaming sources, DVDs, and Blu-rays. The thing I dread the most from other TVs is the “soap opera effect” that happens when watching movies on them. Of the new TVs out there, which are the best at reproducing movies without the soap opera effect?
– Joe Hamilton (salputrid)
A: You’re not alone. Many videophiles hate the soap opera effect (SOE) because it makes movies look like video. SOE occurs when a TV performs a function called frame interpolation, aka motion estimation/motion compensation (MEMC) on movies sent to the TV at 24 frames per second (fps).
All modern TVs are based on LCD or OLED flat panels that display video using a technique called “sample and hold,” in which each frame is displayed on the screen for its entire duration. When viewed this way, objects in motion relative to the camera (whether it’s the object or camera in actual motion) can look quite blurry. Of course, each frame is essentially a still photograph, and objects in motion relative to the camera will be blurry because they are moving while the shutter is open, but sample-and-hold displays make that blurriness worse as your eyes try to track a moving object.
To address this problem, modern TVs can flash the illumination source (backlight in LCD TVs, OLED panel directly in OLED TVs) on and off several times per frame. Plasma TVs do this automatically because of how they work, displaying each frame as many as 10 times. This is often called “sub-field drive,” and it’s one reason plasmas are generally considered to display motion better than LCD or OLED TVs.
To further overcome the blurriness of sample-and-hold displays, many LCD and OLED TVs can also use frame interpolation. In this process, the TV’s processor compares consecutive frames in the signal, identifies objects in motion, and synthesizes new frames in which moving objects are placed where they would be if the scene had been captured at a higher frame rate. This process is illustrated in the graphic above. This sharpens motion detail significantly, but it also introduces the dreaded soap opera effect.
The solution is quite simple: Disable frame interpolation, which is typically enabled by default in the TV’s picture menu. If frame interpolation is disabled, the TV will display each frame several times, depending on the frame rate of the source and the refresh rate of the TV. For example, if the TV has a refresh rate of 120 Hz and the source is 24 fps, the TV will display each frame five times. If frame interpolation is enabled, the TV will synthesize four new frames for each frame in the source signal. (BTW, TVs with a 60 Hz refresh rate do not perform frame interpolation, so this discussion is moot if you have one of those TVs.)
In many cases, if you disable frame interpolation, you can still use backlight flashing to sharpen motion blur, because that does not introduce SOE. However, it does reduce the brightness of the image, since the backlight is off during part of each frame’s duration. If motion is still too blurry for you, many TVs provide a “strength” control for frame interpolation, so you can enable it at a low setting to sharpen motion detail without adding much SOE.
When shopping for a new TV, look for models that provide separate controls for backlight flashing and frame interpolation. Unfortunately, these controls are not always easy to identify, since manufacturers give them different names. For example, in Samsung’s QLED TVs, backlight flashing is called LED Clear Motion, and frame interpolation is called Auto Motion Plus.
In addition, some manufacturers, such as LG, Samsung, and Sony, provide separate frame-interpolation strength controls for content at 24 fps (movies) and 30/60 fps (video). If you hate SOE on movies, set the 24-fps control to 0 and the 30/60-fps control to whatever you like. SOE isn’t nearly as objectionable on 30/60 fps content, since it’s video by definition. On Samsung TVs, these two controls are called Judder Reduction for 24 fps movies and Blur Reduction for 30/60 fps video. They become active and available to adjust when Auto Motion Plus is set to Custom. Other brands offer similar controls.
If you’ve got an AV question, please send it to AskTheEditors@avsforum.com.