120Hz Displays

120 Hz displays are somewhat though to be a Holy Grail. In order to deal with both 720p60/1080i60 deinterlaced to 1080p60 and 1080p24, displays had to support 60Hz/72Hz or 60Hz/96Hz. This increased the cost of manufacturing because the TV needed to sync at multiple frequencies. With the advent of 120Hz displays, both 60fps and 24fps content can be displayed without judder. There’s just one catch.

All 120Hz displays are not created equal.

The faster frame rate of the display allows two additional technologies to be introduced. One is inter-frame interpolation. In this video processing mode, the position of moving objects is “estimated” in the intervening 1/120 second. This creates images that look smoother and more lifelike as viewed through a window. This is similar to the Pixel Plus technology used in Philips and Bang and Olufsen TVs (marketed as Trimension for HTPCs). It also allows some manufacturers to insert dark frames to increase the paunchiness and black levels of a display.

In the perfect world, you could have user selectable features for all three technologies. 24fps content? Display it natively to avoid motion judder and preserve the true film-like experience. Sporting event? Use inter-frame interpolation to make it more life-like. Want better black levels at the expense of brightness? Enable black level insertion.
While some manufacturers have adopted the above, in the real-world there are some manufacturers who only have a subset of those features. That is, they will take 24p images, convert them to 1080p60 (introducing motion judder), and then double that to 1080p120, potentially ruining the intended effects of the Director of Photography or movie director.