I have wanted to write this article for the longest time, because every time someone mentioned the topic, the few strands of hair left on my head were standing up in annoyance. This article is going to offend a lot of people, but I don’t really care because ultimately everyone is wrong about Filmmaker mode and motion smoothing.
Let’s get this show on the road then!
The 24fps Judder
Movies in the cinema run at 24fps (frames per second). This is partly because of legacy reasons:
- It looks good. While it isn’t the minimum for our eyes to see still images as a moving picture, as silent movies were shot with even less fps, it is the minimum that looks pretty – at least at the brightness level cinemas are projecting at – more on that in a moment.
- It was pretty much the minimum fps to be able to start syncing audio to the picture as sound in movies was introduced in 1926
- It was also likely because of cost savings: it is cheaper to shoot at 24 fps than higher frame-rates as that expensive film stock lasts longer, so they agreed on the bare minimum that was needed for audio-syncing.
However, when the camera shoots at 24fps, there is a certain amount of motion judder introduced. It is especially visible when the camera pans front left to right (or vice versa) slowly.
As a solution to the annoying judder for home audiences, display manufacturers have started coming up with motion smoothing, or motion interpolation technology, which estimates and adds extra frames to double, triple, quadruple, etc the frames during playback.
Now a lot of the purists were up in arms about this to say that it is best to play back the material at exactly how it is on the disc: at 24fps – or 24p when playing back on a progressive display which is pretty much all displays nowadays.
More recently, studios banded together to create filmmaker mode, which disables all unnecessary display processing – including motion interpolation – on the display. Now, I am not against filmmaker mode as there are a lot of good things about it, but they are wrong about motion smoothing.
We said earlier that the motion judder in 24fps is annoying and visible. But is it…?
The Display Matters
Let’s assume that the display can actually display 24fps as 24p cleanly, as some displays aren’t able to do so. Let me ignore that issue for a moment.
How visible 24fps judder is a display is determined by 3 things:
- The brightness the image is projected / shown at
- The contrast of the display
- Pixel persistence
If you have actually attended the cinema to watch a movie, and then watched that same movie at home without any motion smoothing enabled, you may have noticed that the judder was a lot more obvious on your TV (and probably your projector) than is was at the cinema. This – in great part – has to do with the brightness of the display. The brighter the display, the more obvious the judder is as your eyes fixate on it. A home display can be upto 6x brighter in terms of how it displays mid-tones which is the most important factor here (25nits versus 50nits – 150nits in absolute terms). However, when calibrated to standard, it is 2x as bright.
The second major issue is that our home displays are higher and higher contrast – certainly higher than an optical print or DCI-standard DLP projection – unless you are using a DLP projector at home. If you increase contrast of the display in addition to its brightness, the 24p judder will be even more obvious, as bright elements flash against a darker background.
Thirdly, pixel persistence. Displays that are not as good at switching their pixels on and off and have a sample & hold issue such as LCD, LCOS, etc can introduce extra judder when a bright object is on a black background. The motion trails can be made worse as the display isn’t able to clear the bright pixels quickly enough as an object moves.
Motion Smoothing or No Motion Smoothing
So I don’t agree that disabling all motion smoothing on modern displays is the equivalent to showing a 24fps movie in the cinema, at least not perceptually.
However, I do agree that some implementations of motion smoothing leave something to be desired as it introduces something called “the soap opera effect” whereby a movie starts looking like a cheaply shot TV show.
But a lot of companies are now catching onto this and have massively improved their motion smoothing algorithms in recent years. If I only look at what JVC has done with their DILA projectors. When I first started watching my RS25 (HD950), I was annoyed that the 24fps judder was a lot worse on it than in the cinema – due to contrast and pixel persistence – but their newly introduced Clear Motion Drive was absolutely awful with film material.
Fast-forward to the RS500 / X7000 onwards, and the CMD implementation on the low setting became a lot more like emulating an optical print at half the brightness and many times less the contrast, while motion enhance was introduced to solve the bright object on dark background motion trails – with some success.
The same goes for LG OLEDs: when set up judiciously, motion smoothing works wonders to remove the extra visible judder that should not be there with film material originally shown on a less bright and less contrasty projector.
James Cameron’s Support of Filmmaker Mode
James Cameron is obsessed with film picture, to the point that he created 25+ colour transfers for this movie Avatar for cinema release to align with the different light levels the cinemas were showing the movie, just so everyone could – perceptually – see the same turquoise – and other colours even if they only occupied the other 1% of the picture. Now that’s obsessive.
Even though James Cameron supported the introduction of Filmmaker Mode, during a recent interview about Avatar: The Way of Water, he expressed the same view I have had for years: disabling motion smoothing on a high-luminance, high-contrast display is NOT equivalent – perceptually – to showing the same movie at the cinema.
Finally, finally, finally, some bloody sense. I wasn’t going mad after all!
I have been trying to find the interview obsessively for the last hour. I am not sure if it was in print or YouTube, but will post it when I do. If you find it first, please post it the comments section. Considering how late this article is- by about 20 years – I am pressing publish – Cameron or no Cameron.
Do YOU have to use motion smoothing in your own home cinema? Absolutely not. You should use the setting that feels the most natural to your eyes and the least distracting. After all, that is all that matters.
However, I wanted to challenge the status quo because I’m sure I’m not the only one who finds judder somewhat more distracting on high-brightness, high-contrast displays. If you are in that camp, you are not alone. I hear you.
Now this doesn’t mean I use motion smoothing on all displays. I didn’t with my Epson UB6050, because firstly the implementation was awful, and secondly it didn’t really need it as the Epson isn’t what I would call high contrast, it is in the ballpark of a high-end DCI cinema projector.
But with an OLED or JVC projector, or even my QLED, I prefer to use it on low.
Again, your mileage may vary, and you are the only expert in your own setup.