Digital cinema projection vs. frame rate

[Will J. Lokken]

Topic: Smoother HFR / frame interpolation / soap opera look.

I just came back form watching Dracula Untold in a spanish cinema (specifically the Yelmo Cineplex Icaria movie theatre in Barcelona).

The movie has pretty great visuals, but something felt wrong. It didn't have the cinematic feel I'm used to and love. After a few seconds I was sure the movie was played in 30fps or more. But after checking out imdb to find out that the film was shot on Kodak I am not so sure any more.

The first time I came across this in cinema (other than of course The Hobbit) was watching A Million Ways to Die in the West (shot on Sony F55) in a Danish Cinema (Cinemaxx Copenhagen). The way this movie was projected definitely looked like 30fps or more, and felt cheap --
20 minutes after A Million Ways to Die in the West had ended, we watched 22 Jump Street (shot on Alexa XT) -- and this movie had none of the high frame rate / frame interpolation feel. Same cinema. 22 Jump Street felt like a real movie.

I can't seem to find out at what frame rate either Dracula Untold or A Million Ways to Die in the West was shot nor at which it was intended to be projected in Cinema --

But my real worry is this,

Are some digital cinemas beginning to use frame interpolation to smooth out motion jitter etc. like popular consumer TVs?

Note: The DVD version of A Million Ways to Die in the West feels right. I'm pretty sure there is some frame rate related gimmick going on. Any ideas or thoughts?

[Carl Looper]

It's conceivable (but I wouldn't know what the actual story is) that a digital projection system might be able play otherwise 24 fps originated material at a higher rate, ie. with interpolated frames inserted. There's certainly no technical impediment to such. Consumer technology seems to pave the way these days for "innovations" in higher end systems.

 

Why such systems would do it is another story. The brain is quite capable of interpolating motion itself. And seems to do a far better job of it anyway. One can assume the brains behind certain technologys may not agree with this.

 

C

[David Mullen ASC]

24 fps print projectors use a double-bladed shutter to flash each frame twice to reduce the perception of flicker, so there are 48 flashes per second in a movie theater. It has nothing to do with making motion smoother. I believe digital projectors do something similar in terms of refresh rate, but it may be even higher than 48 Hz.

 

"A Million Ways to Die in the West" was shot at 24 fps so it couldn't be shown at 30 fps without everything looking a bit sped up. That certainly would be an incorrect way to show the movie. It had an extremely clean, saturated look from using the Sony F65 and F55 so that may have contributed to someone feeling that it looked less filmic than something shot on the Alexa.

 

No, movie theaters don't use super-high refresh rates like 120 Hz and "motion flow" frame interpolation technology to smooth everything out.

 

However, theaters do switch between 3D and 2D all the time and I guess there's a chance that a 2D movie could be screwed up somehow by using 3D "Real D" settings. Not sure because I've never personally seen a problem like that.

[Will J. Lokken]

I agree the clean saturated look looks less filmic but what I am referring to is something different -
The 25 fps DVD i have of A Million Ways to Die in the West looks right. So it must have been the way it was projected in cinema.

It may just be that someone screwed up something with 3D / 2D settings, or that they use a higher refresh rate than 48 hz.
- I guess the only way to be sure is to contact the Cinema. I will give word if the cinema can answer my question.

[Anthony Schilling]

I've been noticing the same problem with a lot of newer flat screen TV's that make shows like "Bonanza" look like 30fps video. We talked about it on another forum and it has to do with a motion smoothing feature not being disabled, at least with flat screen TV's. I see it in bars, stores, at friends houses ect. But the funny thing is that no one seems to notice that anything is off when film is playing like video. Now I'm not all that familiar with the technical details of running a digital cinema projector, but if it has features like that of a newer flat screen which need to be disabled, there is a very good chance that some projectionists and most audiences won't raise a question.

[Paul Bakaus]

David is correct, digital projectors refresh even more often than 48 times to reduce flicker, common standard is 72, often up to 96. Like he also said, more refreshes doesn't improve motion, it just makes the black phase between frames shorter to reduce the fusion flicker threshold (if the screen is black for > 16ms, we perceive it as flicker, and our peripheral vision is even more unforgiving, so a a high valueto reduce makes sense).

 

So sadly not an answer to what you perceived, but thought it might be relevant/interesting anyway. Shameless plug, a more detailed explanation about movie projectors (and the various other display types) can be found in my guide here: http://paulbakaus.com/tutorials/performance/the-illusion-of-motion/.

[David Mullen ASC]

I've been noticing the same problem with a lot of newer flat screen TV's that make shows like "Bonanza" look like 30fps video. We talked about it on another forum and it has to do with a motion smoothing feature not being disabled, at least with flat screen TV's. I see it in bars, stores, at friends houses ect. But the funny thing is that no one seems to notice that anything is off when film is playing like video. Now I'm not all that familiar with the technical details of running a digital cinema projector, but if it has features like that of a newer flat screen which need to be disabled, there is a very good chance that some projectionists and most audiences won't raise a question.

 

I don't think motion interpolation is standard in digital cinema projectors in theaters and I don't think it would be allowed anyway by the DCI standards.

 

But in terms of home cinema, look at this petition:

https://www.change.org/p/hdtv-manufacturers-please-stop-making-smooth-motion-the-default-setting-on-all-hdtvs#share

[John E Clark]

 

I don't think motion interpolation is standard in digital cinema projectors in theaters and I don't think it would be allowed anyway by the DCI standards.

 

But in terms of home cinema, look at this petition:

https://www.change.org/p/hdtv-manufacturers-please-stop-making-smooth-motion-the-default-setting-on-all-hdtvs#share

 

I hope that remains the case for theater projectors...

 

I personally don't upgrade my display frequently, and so I've not had to be confronted with finding a display that adds all these unwanted features...

 

One thing that I have noticed is that the value for 'open gate' illumination of the theater screen for Film film use to be 16 ft-Lamberts, whereas for digital I've been seeing 14 ft-L... I don't know if 2 silly ft-L's makes a big difference, but if a theater reduces it even further I suspect the image may look 'murkier' than may have been intended.

 

The other thing with 3-D is it seems that each projector is projecting at 7 ft-Lambers, for a total of 14 with both 'on'...

 

This of course is for a theater that has been 'tuned up'... but many theaters use to run the projectors lower to make the bulbs last longer...

[Carl Looper]

Yes, the "refresh rate" (mechanical or digital) is something altogether different from the frame rate. And motion interpolated frames are not to be confused or conflated with refresh rate. Motion interpolated frames allow the frame rate to be altered without altering either the refresh rate or the "speed" of the motion, ie. a work originating on 24fps, can be made to play at 30 fps (or any other fps) without the action being speeded up. Because the process involves adding new frames to the work - not duplicate frames but new frames - interpolated from existing ones, using computed motion vectors to determine what this new frame should look like.

 

So for example, a 24 fps work could have 24 new frames (per second), inserted into the image stream (in real time), the result being a total of 48 different frames. And these would then be shown at 48 frames per second. Quite independantly of the refesh rate.

 

One can imagine the possibility of a cinema venue using digital projectors which might very well employ such techniques. I have no idea if there are any rules against the use of such projectors. I myself certainly wouldn't want such techniques being employed as just a matter of course. But if such techniques were being used by a filmmaker in their production workflow, that would be an entirely different thing. There, the filmmaker has the opportunity to customise the way in which such might be used. For example it is an important technique in special effects work. It has it's origins in "match move" techniques as much as other work such as video compression. It emerges within the general field of "machine vision".

 

Carl