Feature Article: What exactly is HFR 3D?

Steve Withers

Reviewer
An explanation of High Frame Rate (HFR) technology

With the release of The Hobbit last week, you might be wondering what all this talk of HFR, high frame rates and 48 frames per second is about?

Read the article here
 
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DrGekko

Well-known Member
Great article, thanks for explaining the history and reasons behind the experiment.
 

True Romance

Distinguished Member
Thanks Steve. I know there are a few posts on this subject already but if 24fps has been the standard for over 80 years surely we're due a change? Like all new things people tend not to like change but over time come around to the new tech or whatever it may be. Not yet seen the Hobbit but when I do I'll be searching out a HFR showing to see what all the fuss is about.
 

AngelEyes

Distinguished Member
Thanks Steve. A nicely written article, it was great to get an insight into the history of the medium.

Adam :)
 

Steve Withers

Reviewer
I know there are a few posts on this subject already but if 24fps has been the standard for over 80 years surely we're due a change?
Isn't that like telling an artist to stop using brushes and paint because you can do it in a computer instead?
 

Marc

Well-known Member
i'm assuming this won't be available on blu-ray as the majority of tv's can't accept anything more than 1080p24 in 3d even if they are really doing 48/72/96 hz?
 

DodgeTheViper

Moderator
Steve,

What a fantastic read, so well put together, understandable and fascinating :thumbsup:
 

DrGekko

Well-known Member
Whilst it would be great to see side by side comparisons of 24fps vs HFR, I don't really want to fork out a tenner and few hours of my time for the experience... not sure whether demos would be available on youtube etc. or on test discs where the projector freq. can be altered?

Steve, when you were referring to the "soap opera effect" - is this the same thing as old 80's episodes of Neighbours and Home And Away?? Also, comparing TV shows from the US and UK in the 80's, US shows appear quite soft and stylised (any show eg. TJ Hooker, Knight Rider, Starksy & Hutch) compared to the drab, very "real" and unstylised effects as seen in productions such as Casualty, Eastenders, Mr Bean etc. - was this to do with framerate or NTSC/PAL??
 

True Romance

Distinguished Member
Isn't that like telling an artist to stop using brushes and paint because you can do it in a computer instead?
True and a good example, however artists didn't use paint and brushes just to save costs which seems the main reason for using 24fps.
 

Krullhero

Member
Great article Steve!

I've seen The Hobbit twice; first in Imax 3D 48fps and then 3D 24fps. Being a massive LOTR fan, I couldn't wait to see the film and I was also excited about the 48fps, despite the criticism the preview received.

When the film started, my heart sank somewhat. I didn't like it at all. Exactly like the intelligent frame creation on my ST30, albeit, without the artifacts. About halfway through the film, I began forgetting about the HFR and enjoying the film but afterwards my biggest complaint to my friends and family was the HFR.

So I then went to see it in good 'ol 24fps and as soon as it started, I felt like ":clap:"..... I wish I had seen it first in 24fps, then 48fps! Enjoyed the film a lot more as I wasn't distracted and I even thought that it made some of the less accomplished sfx look much better, or the lower frame rate was more forgiving.

I can see the appeal to some film makers for using HFR. The action sequences were crystal clear, the fast 'flying' shots in the goblin town and camera pans extremely smooth. In 24fps some of the action was a bit blurry, which was probably due to the fact that PJ was shooting in 48fps and was able to move the camera around faster and still retain a high level of detail. I'm sure many people will like it and many may not even notice a difference.... Like my mum!

I am now looking forward to watching the film in good ol' 2D :thumbsup:

Phil C
 

Steve Withers

Reviewer
Steve, when you were referring to the "soap opera effect" - is this the same thing as old 80's episodes of Neighbours and Home And Away?? Also, comparing TV shows from the US and UK in the 80's, US shows appear quite soft and stylised (any show eg. TJ Hooker, Knight Rider, Starksy & Hutch) compared to the drab, very "real" and unstylised effects as seen in productions such as Casualty, Eastenders, Mr Bean etc. - was this to do with framerate or NTSC/PAL??
When people talk about "soap opera effect" they mean the distinctive look of material shot on video like Neighbours and Home and Away. Interestingly a lot of US TV shows in the 70s and 80s were shot on 35mm but they were often transferred to video for editing, whilst in the UK the BBC would shoot location footage on 16mm and in the studio use video. This in part explains the disparate look of a lot of TV productions back then but transferring NTSC to PAL was also a factor with US shows.
 

Steve Withers

Reviewer
i'm assuming this won't be available on blu-ray as the majority of tv's can't accept anything more than 1080p24 in 3d even if they are really doing 48/72/96 hz?
You are correct plus Blu-ray is limited to 24p and even if they weren't, I think you struggle to fit an entire 3D movie at 48 FPS on a single Blu-ray
 

MikeTheBike2010

Active Member
Many thanks for a great article Steve.

Having been asked at work "well what rate does film usually run at" (a groan went round the office as everyone knew Id have an answer) I agree with the "my mum didn't notice" as lots of the public just are not that interested.

Having yet to see the film I remain intrigued by 48fps content (although I enjoyed Universal Studios Back to the Future ride which I believe was filmed in high rate "Showscan" and failed to notice anything different myself?).

Mind you with many critics pointing out the long running time has anyone thought of just projecting the 24fps through 48fps software to reduce the running time (only joking and think I have that the right way around!).

A merry Christmas to you and all at AV forums, many thanks for the entertainment and information through the year.
 

Duvetdo

Novice Member
Great article. I have seen The Hobbit at 48 FPS, having read up on the pros and cons beforehand. I agree that it does make it more 'realistic' and I'm 50/50 if that makes it 'better' or not. I do agree that it makes it seem like a play on the screen, but did not pick up on a 'soap-opera effect', unless, of course, these two things mean the same!

I swallowed the 3D hype (shame on me) and bought a 42" Panasonic last Christmas. Have since watched the grand total of 2 3D films at home. The Hobbit was the first cinema visit in 3D and it works so much better when all you can see through the glasses is the screen.

What I am excited about is Dolby Atmos and I'm looking forward to Steve's comparison after his second viewing of The Hobbit on the 22nd.
 

Scooby2000

Distinguished Member
Wonderful article, thanks Steve, I have the same concern myself.
I can see both arguments for and against and maybe this is a generational shift and the smoother look will be the norm in ten twenty years.
Id be interested to see the effect on 3D, but in 2D I don't want it to look to real as its a fantasy film, it may just look like what it is, people in costume and CGI.

Not seen it yet waiting for subtitles to go see it with my deaf mate.
 

Mr.D

Distinguished Member
?? Also, comparing TV shows from the US and UK in the 80's, US shows appear quite soft and stylised (any show eg. TJ Hooker, Knight Rider, Starksy & Hutch) compared to the drab, very "real" and unstylised effects as seen in productions such as Casualty, Eastenders, Mr Bean etc. - was this to do with framerate or NTSC/PAL??

Yes but the soft and styled look on the US series filmed on 35mm at 24fps could alos primarily be down to poor transcoding from NTSC to PAL. A lot of shows used to generate a proper PAL master by running the film at 25fps ( exactly the same as PAL movie transfers). These shows still look great in comparison to even much later transcodes.

(ST:OS and ST:NG a case in point)

The general difference in look between natively captured 24fp and 48fps is down to motionblur and sampling rate (temporal). Film cameras generally shoot at 24fps with a rotating circular shutter in front of the film path to provide a further moderator mechanism for exposure . Nominal 24fps film capture uses a shutter angle in the region of 180 degrees . This gives a capture interval in the region of 1/48 of a second per frame. The 1/48th of a second exposure is responsible for the hallmark film motion presentation.

A larger shutter angle results in a capture interval approaching 1/24th as its opened all the way ( film cameras do not usually have a fully openable shutter but I digress). This results in a visual depiction that looks "smeary'.

The opposite is to use a smaller shutter angle which results in a smaller capture interval which lessens the mtionblur captured for moving detail. Gladiator and saving private ryan cases where this effect is used deliberately and is often misinterpreted as being sped up or frame culled.

The Hobbit was shot 48fps with a minimal shutter time the idea being that each frame would have a similar level of motionblur as 24fps capture ; this aos enable it to be easily frame culled to 24fps for regular presentation again with a level of motionblur that the audience is familiar with.
 

Steve Withers

Reviewer
That's a good point about the shutter angle, they used 270 degrees when filming The Hobbit in order to address limitations in the RED Epic when shooting at 48 FPS and in 3D, which might explain the overly smooth motion in the HFR version.
 

warrenoates

Active Member
Er,but no mention of Douglas Trumbel?? He's been banging on about increased frame rates since the early 1970's !
 

Steve Withers

Reviewer
I didn't want to get side tracked by talking about Douglas Trumbull and Showscan but as you say he has been pioneering large format/high frame rate photography for years with Showscan using 65mm and 60 FPS. However, Showscan was never used for film production or theatrical distribution, although Trumbull has used it very effectively in his theme park rides.
 

Mr.D

Distinguished Member
That's a good point about the shutter angle, they used 270 degrees when filming The Hobbit in order to address limitations in the RED Epic when shooting at 48 FPS and in 3D, which might explain the overly smooth motion in the HFR version.
No the motion is down to the increase in temporal sampling rate ; 48fps vs 24fps , the capture interval on each frame is 1/48 (give or take ; 90 degree on a shutter angle will produce very little change in motionblurwhen its that wide open) Its essentially open shutter so the frame rate is predominately dictating the exposure time ergo...1/36th per frame . 1/36th to 1/48th is within the range of nominal on a 24fps film camera. I kinda suspect that the reason for using this on the RED was to minimise some sort of artifact from the cmos sensor as it builds a frame by line at a time. I'm betting that they found something incompatable with the 24fps culling process or an increase in jellyvision ( I'll ask them when I meet up on Christmas Eve)

This is the same (near enough) as the capture interval on 24fps capture shot with a nominal 180 degree shutter angle.

The point is that each frame on the Hobbit whether you are watching the 24fps version or the 48fps version has near as dammit the same motionblur characteristics as natively shot 24fps material.

This is why they can create a 24fps version that seems little different to nominal 24fps captured materail; its just a simple process of culling out every other frame. If they had used a 180 degree shutter angle when capturing at 48fps it would have looked fine on 48fps playback but would be very strobey when culled to 24fps playback. (like Gladiator fight scenes for the entire film)

The difference in motion presentation is entirely down to the increased sample rate , its not a question of it having less motionblur than 24fps material. People who keep stating this have gotten the wrong end of the stick. Jackson himself has even mistated this. (not so surprising that he isn' t terribly deeply into the technical fundamentals of image capture)

Incidentally I'm standing next to a 435 arri film camera on a film shoot and I have known and worked with most of the senior staff at Weta before Weta even existed.
 
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Steve Withers

Reviewer
The point I'm making is that I wonder what 2D 48 FPS looks like when a 180 degree shutter angle is used because, whilst I expected the increased frame rate to smooth motion, I was surprised at how bad it looked.
 

borgib

Novice Member
superb article!!!

I saw the Hobbit in HFR 3D the other night and i found it was a bit hit and miss. whilst it certainly got better towards the end (the rock giant sequence was a scene that defines the cinema experience) i found the shots that gave the impression of an artifically speeded up look too distracting like when Bilbo is putting plates away at the start
 

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