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nuttall_chris
Joined: 08 Mar 2006
Posts: 832
Location: Ottawa, Ontario, Canada
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Person99
Joined: 09 Mar 2006
Posts: 4899
Location: Flower Mound, TX
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| Posted: Thu Nov 20, 2008 7:09 pm Post subject: Re: The Big Judder Problem and the Overhyping of 24p |
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Is this guy a moron? Of course 24 Hz judders it is only 24 frames per second my god--that is why wagon wheels look like they are going backwards! No revelation here!
Second, the fact that a theater uses a 2 bladed or 3 bladed projector to display it at 48 Hz or (more commonly 72 Hz) does not make it smoother--it is the same frame shown 3 times--the judder is still there. What a moron.
Now, any digital display does one of two things with a 1080p/24 signal (if it accepts it):
1) Convert it to a multiple of 24 (typically either 48, 96, or 120).
2) Convert it to 60 Hz.
60 Hz introduces yet another judder. In addition you have the 24 fps judder, plus the 3:2 judder--that is terrible!
But, this idiot seems to think that that films inherent 24 Hz capture rate needs to be fixed. But, since it is not "fixed" at the source, he wants to "fix" the "problem" at the display with interpolation. Who gives a f*ck that interpolation introduces its own artifacts and makes the material look really f*cking odd to most viewers (because they've never seen film like that so it doesn't look "right").
So, the wait continues...will projector central EVER publish ANYTHING that is worth reading?!?!?!?
So, 1080p/24 is NOT overhyped. If displayed at a multiple of 24, then you come much closer to the artists intent then you do with 3:2 pulldown--and that is the problem it is intended to address.
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Dave
A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station....
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Thu Nov 20, 2008 7:16 pm Post subject: Re: The Big Judder Problem and the Overhyping of 24p |
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| Person99 wrote: | | Second, the fact that a theater uses a 2 bladed or 3 bladed projector to display it at 48 Hz or (more commonly 72 Hz) does not make it smoother--it is the same frame shown 3 times--the judder is still there. |
A bit OT, but... I've always wondered WHY they use those blades.
I know the basic idea of the blade is to block the light while the film moves to the next frame, so you don't see the dark band between frames or see blurred images because the film is moving. That makes perfect sense.
But what's the advantage of "flashing" each frame 2 or 3 times? Why not just block the light when the film is moving, and then leave it ON the whole time the film is still? Is it to protect the film from excessive heat, or...?
I would think a non-"flashy" projector would have higher light output and would look less flickery. There must be a reason for doing it but I'm not sure what it is.
BTW running a CRT projector at 2x or 3x the 24p speed makes perfect sense, since with CRTs you *can't* run them at 24p like I'm suggesting for film projectors. The CRT tube can't hold the image for the full 1/24th sec like the film projector can.
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Person99
Joined: 09 Mar 2006
Posts: 4899
Location: Flower Mound, TX
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| Posted: Thu Nov 20, 2008 8:16 pm Post subject: Re: The Big Judder Problem and the Overhyping of 24p |
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| garyfritz wrote: | | Person99 wrote: | | Second, the fact that a theater uses a 2 bladed or 3 bladed projector to display it at 48 Hz or (more commonly 72 Hz) does not make it smoother--it is the same frame shown 3 times--the judder is still there. |
A bit OT, but... I've always wondered WHY they use those blades. |
flicker. Your persistence of vision isn't enough. Think about the flicker in the old silent movies. Those were shown at true frame rate.
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Dave
A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station....
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Thu Nov 20, 2008 8:32 pm Post subject: |
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There's also something wrong with that reviewer's setup.
The Casino Royale walking scene is fine on my PC.
(But the card table pan is horrid).
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Thu Nov 20, 2008 8:40 pm Post subject: Re: The Big Judder Problem and the Overhyping of 24p |
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| Person99 wrote: | | flicker. Your persistence of vision isn't enough. Think about the flicker in the old silent movies. Those were shown at true frame rate. |
I don't buy it. I'd bet the old movies spent more time blacked out, and less time with the image showing.
Let's say in current projectors the film spends 20% of its time moving to the next frame. **IF** you keep that constant, then I claim having the image on for 80% of the time will produce LESS flicker than having it on 30%, off 20%, on 30% (or whatever). That blackout between the duplicate frame display reduces light output and would, I would think, INCREASE perceived flicker.
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Thu Nov 20, 2008 8:48 pm Post subject: |
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The reason they show film at 48hz (which still flickers like buggery), is to reduce flicker Gary.
So there must be some technical reason why they can't hold the frame lit up for a longer duration and display at 24hz (like maybe the film would melt).
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ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
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| Posted: Thu Nov 20, 2008 9:21 pm Post subject: Re: The Big Judder Problem and the Overhyping of 24p |
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| garyfritz wrote: | | Let's say in current projectors the film spends 20% of its time moving to the next frame. **IF** you keep that constant, then I claim having the image on for 80% of the time will produce LESS flicker than having it on 30%, off 20%, on 30% (or whatever). That blackout between the duplicate frame display reduces light output and would, I would think, INCREASE perceived flicker. |
And you'd be wrong, Gary! The faster the rate at which something flickers, the less sensitive the eye and brain are to the flicker. By adding a second black period in the middle of the displayed film frame, it actually makes the both flickers less noticeable than would one be. It's exactly the same principle that made 60hz refresh on some computer CRT monitors very noticeable - annoying even - but where 75hz was practically imperceptible on the same monitor. Of course, that was both increasing the number of refreshes, and shortening the duration of the refresh.
SC
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ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
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| Posted: Thu Nov 20, 2008 9:22 pm Post subject: |
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To be honest, I don't think the author of that article has a really good handle on the subject.
First of all, recording something at 24hz and playing it back at 24hz does NOT result in judder. There is no such thing as "film judder". Everybody who calls it that, uses the term incorrectly. Judder is SPECIFICALLY the motion artifact that results from playing back content at a frame rate different from which it was recorded - i.e. playing back 24hz content at 30 or 60hz. Judder is the result of displaying a sequence of frames for different amounts of time - which doesn't happen in the theater, or anywhere else program material is displayed at its NATIVE refresh rate.
I suspect the author is using a low-end digital projector that accepts a 24p input, but is still displaying at 60hz (adding 3:2 pulldown), and therefore displays film-source material with judder regardless of how he has the source or projector set up. It probably looks the same or similar, but he thinks it's different when he switches his BD player to output 60hz. That, or the resulting picture really is subtly different depending on how the processor in the BD player vs. the projector adds frames (3:2 pulldown) to display 24p source material on the 60hz native display.
This paragraph is particularly telling:
| Quote: | | In 24p playback, this scene is a pure, unmitigated disaster. The people seated at the table come apart at the seams, the tuxes flash and strobe, the Casino Royale logo on the card table blinks like a neon sign. Once you've replayed this travesty a few times, switch your Blu-ray player to 60p output and run it again. Yes, it is still a mess. But look at it closely ... the juddering effect is actually reduced. That is because the 3:2 pulldown is blurring and masking some of the latent motion judder in the film. There is certainly a separate conversion judder that is added to the visual stew with 3:2 pulldown, but oddly enough it works in contravention of the latent 24p judder. The net effect is that the image is a bit blurred, and the overall judder is noticeably reduced. Scenes like this do not look great in 60p, but they look worse in 24p. After all the hype over 24p (the benefits of which we eagerly anticipated as much as anyone), it must be admitted that 60p playback can, in the final analysis, be less distracting for many people. |
I don't know what the F he's talking about, but there should be no BLURRING of any kind unless something's wrong or misconfigured in his setup. We're talking about temporal frame rate conversions. There should be nothing at all spacial going on unless we talk about different kinds of i-to-p interpolation. There should simply be no blurring of any kind if we're staying at 1080p, but just comparing 24p and 60p. That's why I think something is F'ed up in his system.
The judder effect is probably reduced when he switches from 24p to 60p output on the BD player, because the video processor in either his projector or the BD player sucks ass. Either the frame rate conversion is borked in the projector making it more "judder-y" than it should be, or the processor in the BD player is doing something wrong making it look blurry or smoother than it should.
SC
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kal
Forum Administrator
Joined: 06 Mar 2006
Posts: 18114
Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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| Posted: Thu Nov 20, 2008 9:32 pm Post subject: Re: The Big Judder Problem and the Overhyping of 24p |
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100% agree with you Dave. So many things wrong with what he writes like:
| Quote: | | "Actually, we've never seen 24 fps film quite this naked even in a commercial movie theater since the double shuttering action of the movie theater's projection system reduces the experience of judder and flicker." |
Errr, what? The double shuttering action is to remove flicker. It does nothing for judder.
Like you said, he really needs to say that he has an issue with film being shot at 24 fps and nothing else. That in itself is a whole other ball of wax and frankly, he can't be too much of a movie buff if he doesn't appreciate the 'look' that 24 fps gives a film. They could have gone to higher frame rate film eons ago but cinematographers DON'T want their films to feel like "cheap" video (30fps or even 60fps). They actually LIKE the judder.
Kal
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Person99
Joined: 09 Mar 2006
Posts: 4899
Location: Flower Mound, TX
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| Posted: Thu Nov 20, 2008 9:34 pm Post subject: |
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| ecrabb wrote: | | To be honest, I don't think the author of that article has a really good handle on the subject. |
Hence my moron comment. This is quite typical of projectorcentral.com. They think they know much more than they do!
| ecrabb wrote: | | I suspect the author is using a low-end digital projector that accepts a 24p input, but is still displaying at 60hz (adding 3:2 pulldown), and therefore displays film-source material with judder regardless of how he has the source or projector set up. It probably looks the same or similar, but he thinks it's different when he switches his BD player to output 60hz. That, or the resulting picture really is subtly different depending on how the processor in the BD player vs. the projector adds frames (3:2 pulldown) to display 24p source material on the 60hz native display. |
I'm not sure. Because 24 fps will not smoothly capture motion at "just the right speed". An object can move far enough between frames that you brain can see it "hop". If the pan is fast enough, you don't see it because thanks to the amphibian parts of our visual perception system, with fast motion, we cannot perceive details, only the presence of motion.
So, although he is a moron, I'll give him the benefit of the doubt on this one. 
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Dave
A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station....
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Person99
Joined: 09 Mar 2006
Posts: 4899
Location: Flower Mound, TX
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| Posted: Thu Nov 20, 2008 9:35 pm Post subject: Re: The Big Judder Problem and the Overhyping of 24p |
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| kal wrote: | They could have gone to higher frame rate film eons ago but cinematographers DON'T want their films to feel like "cheap" video (30fps or even 60fps). They actually LIKE the judder.
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Bingo and good point to bring up.
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Dave
A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station....
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Thu Nov 20, 2008 9:57 pm Post subject: |
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| ecrabb wrote: | To be honest, I don't think the author of that article has a really good handle on the subject.
First of all, recording something at 24hz and playing it back at 24hz does NOT result in judder. There is no such thing as "film judder". Everybody who calls it that, uses the term incorrectly. Judder is SPECIFICALLY the motion artifact that results from playing back content at a frame rate different from which it was recorded - i.e. playing back 24hz content at 30 or 60hz. Judder is the result of displaying a sequence of frames for different amounts of time - which doesn't happen in the theater, or anywhere else program material is displayed at its NATIVE refresh rate.
I suspect the author is using a low-end digital projector that accepts a 24p input, but is still displaying at 60hz (adding 3:2 pulldown), and therefore displays film-source material with judder regardless of how he has the source or projector set up. It probably looks the same or similar, but he thinks it's different when he switches his BD player to output 60hz. That, or the resulting picture really is subtly different depending on how the processor in the BD player vs. the projector adds frames (3:2 pulldown) to display 24p source material on the 60hz native display.
This paragraph is particularly telling:
| Quote: | | In 24p playback, this scene is a pure, unmitigated disaster. The people seated at the table come apart at the seams, the tuxes flash and strobe, the Casino Royale logo on the card table blinks like a neon sign. Once you've replayed this travesty a few times, switch your Blu-ray player to 60p output and run it again. Yes, it is still a mess. But look at it closely ... the juddering effect is actually reduced. That is because the 3:2 pulldown is blurring and masking some of the latent motion judder in the film. There is certainly a separate conversion judder that is added to the visual stew with 3:2 pulldown, but oddly enough it works in contravention of the latent 24p judder. The net effect is that the image is a bit blurred, and the overall judder is noticeably reduced. Scenes like this do not look great in 60p, but they look worse in 24p. After all the hype over 24p (the benefits of which we eagerly anticipated as much as anyone), it must be admitted that 60p playback can, in the final analysis, be less distracting for many people. |
I don't know what the F he's talking about, but there should be no BLURRING of any kind unless something's wrong or misconfigured in his setup. We're talking about temporal frame rate conversions. There should be nothing at all spacial going on unless we talk about different kinds of i-to-p interpolation. There should simply be no blurring of any kind if we're staying at 1080p, but just comparing 24p and 60p. That's why I think something is F'ed up in his system.
The judder effect is probably reduced when he switches from 24p to 60p output on the BD player, because the video processor in either his projector or the BD player sucks ass. Either the frame rate conversion is borked in the projector making it more "judder-y" than it should be, or the processor in the BD player is doing something wrong making it look blurry or smoother than it should.
SC |
Umm, 24fps isn't perfect SC, far, far from it.
There are all sorts of rules cinematographers have to observe, and in the card table scene that pan is just too fast - it judders all over the place.
But on my PC, at 96hz, James Bond walking to the hotel was fine.
I noticed quite a few scenes in Cars BD that show the same 24fps limitations, and that is rendered, not photographed.
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ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
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| Posted: Thu Nov 20, 2008 10:16 pm Post subject: |
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| Person99 wrote: | | 'm not sure. Because 24 fps will not smoothly capture motion at "just the right speed". An object can move far enough between frames that you brain can see it "hop". If the pan is fast enough, you don't see it because thanks to the amphibian parts of our visual perception system, with fast motion, we cannot perceive details, only the presence of motion. |
Yep - Our brain masks the frame rate on faster motion, but so does camera/motion blur. In fact, it usually is motion blur (induced by the rotary shutter and relatively long exposures due to low-ISO film) that masks the lower the frame rate in faster-motion scenes.
Mark, I never said 24fps was perfect - and yes, I know - far from it. But the quality of motion from 24fps is much better than 24fps rendered with 2:3 pulldown. If you're calling film juddery, then it's "double-juddery" with telecine.
I'll grant that perhaps you can call motion picture's "jumpiness" "film judder" - and that some do. But, I think it's a relatively modern term - at least as applied to 24fps film motion rendering. IMHO, if we're going to use the term "judder" to refer to several different types of motion artifact, then we should always clearly delineate which one we're talking about. There's "film judder" and 3:2 pulldown-induced judder, or "telecine judder", then. The article didn't delineate at all.
I'd say it's telecine judder that people are usually seeing and have the worst time with, if for no other reason that very few people have a setup in their home that is even capable of displaying film-source material WITHOUT telecine-induced judder. I don't know about you, but I never sat at the theater and thought, "Wow, the judder in that scene was really nasty." OTOH, I sure as hell have sat and looked at a computer screen or projector playing a DVD and thought about it - plenty of times, in fact.
SC
Last edited by ecrabb on Thu Nov 20, 2008 10:24 pm; edited 2 times in total
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Thu Nov 20, 2008 10:23 pm Post subject: |
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| ecrabb wrote: | | Person99 wrote: | | 'm not sure. Because 24 fps will not smoothly capture motion at "just the right speed". An object can move far enough between frames that you brain can see it "hop". If the pan is fast enough, you don't see it because thanks to the amphibian parts of our visual perception system, with fast motion, we cannot perceive details, only the presence of motion. |
Yep - Our brain masks the frame rate on faster motion, but so does camera/motion blur. In fact, it usually is motion blur (induced by the rotary shutter and relatively long exposures due to low-ISO film) that masks the lower the frame rate in faster-motion scenes.
Mark, I never said 24fps was perfect - and yes, I know - far from it. But the quality of motion from 24fps is much better than 24fps rendered with 2:3 pulldown. If you're calling film juddery, then it's "double-juddery" with telecine.
I'll grant that perhaps you can call motion picture's "jumpiness" "film judder" - and that some do. But, I think it's a relatively modern term - at least as applied to 24fps film motion rendering. IMHO, if we're going to use the term "judder" to refer to several different types of motion artifact, then we should always clearly delineate which one we're talking about. There's "film judder" and 3:2 pulldown-induced judder, or "telecine judder", then. The article didn't delineate at all.
I'd say it's telecine judder that people are usually seeing and the worst time with, if for no other reason that very few people have a setup in their home that is even capable of displaying film-source material WITHOUT telecine-induced judder. I don't know about you, but I never sat at the theater and thought, "Wow, the judder in that scene was really nasty." OTOH, I sure as hell have sat and looked at a computer screen or projector playing a DVD and thought about - plenty of times, in fact.
SC |
Yep, I agree now.
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ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
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| Posted: Thu Nov 20, 2008 10:26 pm Post subject: |
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Uh oh, Mark... You and I agree on something. Look out - it could mean the end of the world is near...
SC
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Person99
Joined: 09 Mar 2006
Posts: 4899
Location: Flower Mound, TX
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| Posted: Thu Nov 20, 2008 10:37 pm Post subject: |
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| ecrabb wrote: | Uh oh, Mark... You and I agree on something. Look out - it could mean the end of the world is near...
SC |
Awe, we all agree as one big happy family. 
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Dave
A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station....
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ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
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| Posted: Thu Nov 20, 2008 10:52 pm Post subject: |
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Yeah, one big happy, dysfunctional, whacked-out, bizarro... "family"...
ala Home for the Holidays or Little Miss Sunshine.
SC
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Fri Nov 21, 2008 1:17 am Post subject: |
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Did all the planets just align and is there an eclipse today or something?. SC, Dave AND Mark agreeing at the same time?
"Where's the Kaboom? There's suposed to be an Earth shattering Kaboom!" ~Marvin Martin
I've got my fingers to my ears waiting, while making the wincing face. The one girls make when they know a baloon is about to pop.
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Fri Nov 21, 2008 2:29 am Post subject: Re: The Big Judder Problem and the Overhyping of 24p |
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| ecrabb wrote: | | And you'd be wrong, Gary! The faster the rate at which something flickers, the less sensitive the eye and brain are to the flicker. By adding a second black period in the middle of the displayed film frame, it actually makes the both flickers less noticeable than would one be. |
I could almost believe that, if anybody would point to a reference that says it. It doesn't make sense to me but I could believe the brain acting like that.
| Quote: | | It's exactly the same principle that made 60hz refresh on some computer CRT monitors very noticeable - annoying even - but where 75hz was practically imperceptible on the same monitor. Of course, that was both increasing the number of refreshes, and shortening the duration of the refresh. |
Here I disagree. Faster CRT refresh means you have less decay time between updates, while I *think* the dot intensity is the same. Which means the phosphor glow level is higher with the faster update, so you have less flicker because the screen doesn't get as dark between refreshes. It's a totally different mechanism than film 24/48 blades.
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