Updated: more details on how motion is handled or more precise; look like and its side effects and positive effects on settings, like cinematic movement and Natural setting. The Plasma´s motion did make motion blur(due to 23/24fps)..but so does your sight when you turn your head(objects get out of focus), it is how Your eyes/sight work(s). So if the Tv and movie industry is going to go for 60 fps movies instead of the regular 23.976 fps it will kill off the cinematic feel one gets when viewing a movie. If pictures and motion are more or less clear all the time it will look very artificial and not present how real scenes would naturally look like( altering how You perceive motion, unrealistic motion). You dont need a clear picture all the time..this how you get the action feel of a movie, when an action scene is presented and surprises you or urg the theatrical feel of the movie´s action scenes .
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A tip! Because there are no "right" settings and there are good and bad rendering with all choices, and if one does not want to tweak and see what works and what does not work, and don´t mind some stutters, shivering effects and shimmering effects on moving objects in high contrast scenes, like the opening white room scene in Alien Covenant, one can just set truemotion to cinematic movement (a set and forget motion setting). In general this is a good choice and with this choice one get a more natural motion and less ROBOTIC motion, which too much interpolation does. Also the dreaded SOE-effect is much less visable too. So this is a positive effect by using less interpolation. Most of the times this works well (also I read now that the latest Lg G4 is cheered for the new cinematic movement interpolation setting, which is really good they say). Many movies work ok with this setting, like the latest Batman movie or Jurassic world. Also If You want smoother motion and better panning scenes, choose Truemotion, Natural, instead of using custom settings like de-judder, de-blur and bfi (this lower the brightness significantly and I can not say I have seen any improvement motionwise using bfi), some state that the pre-choices are more fine-tuned and introduces less artifacts. I Am very happy with this setting. but You get as I mentioned a more robotic motion (I also read Sony´s latest Led flagship is still the best on handeling motion(in general Sony has better motionhandeling software, but this is getting very narrow now). On Sony´s tv´s You just set the picture mode to "true cinema/cinema" and You be fine (one does not need to activate custom mode, the tv will handle it all and with very little or no visable SOE effect, if I have understood the Sony settings correct). (custom mode: smoothing and clearness settings is then handled by the Tv´s settings). Also set Cinemotion/Film mode to high and if one experiencing any unwanted rendering like atifacts, then set it at medium or even at low(to make panning look ok)(less chance of flickering to happen I read just now on a avsforum). I also read that set at custom, smoothness at 2, clearnes at 1 and film mode(cinemotion) at low to get smoother panning scenes. This is for best motion. So one just have to try things out and choose what is best for You, what balance one think is best.
In general newer movies works much better with cinematic movement setting, then with Natural setting. Like newer spiderman movies one does not need that much interpolation, which Natural setting provides. Older movies normally need the natural setting to look good. This is because how cameras is used making many of the scenes and the use of much more panning compare to the new movies, one see this very easily with newer Marvel movies. They need less interpolation to look good, because of less usage of panning or really fast paning so one does not notice any unwanted rendering/stutter/artifacts.
For Sony tvs this is a good thread to read:
https://www.avforums.com/threads/sony-motionflow-film-mode-settings-explained-finally.2205593/Update! JRiver version 33´s new presentation mode for JRVR is a very good upgrade, when it comes to rendering videos/movies. Smooth motion and less artifacts(unbelievable!). The new timing of frames and vsync is a very good solution. So the Tvs interpolation give better results by erradicate or reduse artifacts and motion is more consistant and smooth and less chance that stutter or microstutter occur(there still is discrepancy here though, but the culprits to this could be numerous ( gpu, cpu, vsync, nvidia driver, OS and Jrvr). So this is a big upgrade for the JRiver software on how it renders videos.