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Varicam Frame Rate Ramping and Playback


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#1 Thomas James

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Posted 18 January 2008 - 02:25 PM

What I am looking for is 24p in order to preserve the film look and avoid that 60p cheesy soap opera look. On the otherhand I have found that 24p is totally inadequate for fast action. I think that the Varicam offers a powerfull technology in that the framerate can be selected even on the fly. Most people use variable framerates as overcranking for slow motion but what most people do not realize is that variable frame rates can be played back in real time. Thus it is possible to select the exact framerate to coresspond with the motion while still preserving the film look.
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#2 Seth Melnick

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Posted 18 January 2008 - 03:53 PM

I dont think your analysis is correct.

when you play back the footage you play at a constant framerate - like 24 frames / sec

so if you ramp while recording and then play back at a constant rate you will see fast and slow motion but not smoother rendition of motion. To accomplish what you are talking about you would need a variable playback speed in addition to the variable frame rate recording.
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#3 Chris Keth

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Posted 18 January 2008 - 05:30 PM

On the otherhand I have found that 24p is totally inadequate for fast action.


Can you explain this? I see no reason why 24fps isn't adequate for fast motion.
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#4 Thomas James

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Posted 18 January 2008 - 06:28 PM

Barry Green has verified that the Varicam has this capability if the footage is recorded in a 60p stream with pulldown. 20p footage will be recorded repeating each frame 3 times 24p will be recorded by repeating each frame twice and then 3 times. 40p footage will be recorded by displaying each frame once and then the next frame twice. 60p footage will have each frame displayed once. As long as the pulldown is not removed in the embedded stream the footage will not slow down or speed up when played back at least on the average.(for example when 24p footage is played back in a 60p stream the fotage will speed up and slow down due to the 2:3 pulldown but on the average the motion will be constant. Alll of this footage of different framerates will be mixed together.

As far as fast action is concerned most cinematographers capture this action by tracking the subject and use an elaborate system of track and dollies in order to minimize movement. However there are at times impossible shots such as if a cinematographer wants to film cars whizzing by in which case 24p does not offer enough temporal resolution. In these cases shooting at a higher framerate will solve the problem.

However the thing you don't want to do is shoot the entire movie at 60 frames per second because your footage will scream video. For example newer 120 hertz televisions have the capability to upconvert any movie ever made to 48 frames per second but all this does is change the film look to the video look. What I am proposing is that the cinematographer should have control over what framerate is used for playback so that motion picture fidelity can be increased if absolutely necessary but that this is not overdone or else the film look is destroyed. Even the most ardent supporters of the Showscan format have never advocated that the whole movie should be shot at 60 frames per second. My proposal is that the framerate can be even more finely tuned to correspond with the speed of the motion and if desireable to preserve the film look lower framerates than 24p can be used such as 20p or 15p or slightly higer framerates such as 30p and all these different framerates are mixed together.

As far as distribution goes it has been proposed that film prints can be designed to run at 48 frames per second or 60 frames per second.and if slower framerates are desired such as 24 fps each frame can be printed twice. For conventional distribition 24fps prints can be produced from 48 fps masters. But the real future is digital cinema and distribution that will allow on the fly framerate ramping just as the shutter speed can also be ramped.
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#5 Seth Melnick

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Posted 18 January 2008 - 07:53 PM

once again this will NOT give you the effect you are looking for - when the camera uses the frame twice or three times it is the same exact frame so there will be NO motion between the frames.

so as the frames get repeated more it will look studdery but not smoother - you will not be capturing more or less motion

i say again to get the effect you are looking for you need to playback at variable frame rates
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#6 Seth Melnick

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Posted 18 January 2008 - 07:55 PM

one other point is that you cant playback at 15 frames per second and expect it to look the same as 24 frames per second - the image will not refresh enough to approximate motion - there is a reason 24 frames or more are used to show films
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#7 Thomas James

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Posted 18 January 2008 - 08:50 PM

As the frames get repeated the footage will either look more studdery or more blurry but this all depends on how you set the shutter speed and how fast the motion is. 15 frames per second or 4 frames repeated twice may not be adequate for motion but that all depends on how much motion you need to capture. If you are recording in a 60 frame stream you may decide to shoot at 20 frames per secound and playback by reapeating each frame 3 times. This will result in a more even cadence. or you may prefer to shoot at 30 frames and playback by repeating each frame twice. But if you shoot 24p in a 60p stream you will have an uneven 2:3 cadence. If you shoot 60p and playback at 60p your footage will look like video but then again that may be just fine for certain parts of the footage if you want a hyper realistic special effect but if this is overdone it will destroy your movie by making it look like a soap opera.

Even the most arduant advocates of 60 fps movies like Doug Trumble never advocated shooting the whole movie at 60 fps because that would make the movie look like crap but rather mixing 24 fps footage with 60 fps footage the later being used for the virtual reality special effects of the Brainstorm movie starrring Natallie Wood. Nor Did Doug Trumble ever preach a single aspect ratio but rather advocated mixing a 4:3 aspect ratio with a wide screen aspect ratio.
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#8 Michael Nash

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Posted 18 January 2008 - 09:32 PM

once again this will NOT give you the effect you are looking for - when the camera uses the frame twice or three times it is the same exact frame so there will be NO motion between the frames.

so as the frames get repeated more it will look studdery but not smoother - you will not be capturing more or less motion

i say again to get the effect you are looking for you need to playback at variable frame rates



No, actually Thomas is right. If you display the Varicam's footage at 60P (the same rate it records), you will see motion displayed in real time with the appropriate amount of motion blur for the frame rate used during acquisition. "Stuttery" motion is not a problem with 24fps footage, as we're all used to seeing 24fps with a 3:2 pulldown on 60i display (60P display is just as smooth), and motion sampling only gets smoother as frame rates increase to 60fps. So what Thomas is suggesting would actually work in theory; speed ramp between 24fps and 60fps and display that at 60P for variable motion sampling and motion blur, with real-time motion.

As far as Thomas' assertion that 24fps is too slow for action sequences, he's been on this one-man crusade for quite some time. I haven't see any evidence that anyone agrees with the notion, but since it's partly a matter of taste and opinion he's entitled to his own.
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#9 Thomas James

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Posted 18 January 2008 - 10:47 PM

One would certainly think that I must be a die hard 60 frame per second shooter however after counting my video footage I would say that 98 percent of my footage is at low temporal frame rates such as 30p while only 2 percent of my footage has ever been shot at 60p. The reason for this is that most of the time to have the capability to shoot at 60p means shooting at a lower resolution. For Red shooters this means shooting at 2k for 60p rather than 4k at 24p and for typical high definition shooters they must lower the resolution to 720p to get 60p but if they shoot at 24p they can get 1080p. For me it is the choice of shooting 720p at 30 frames per second or 480p at 60 frames per second.

That being said are there times where 60p standard definition can be better than 30p high definition ? Yes there are. Try filming a carousel where the horses not only go around and around but also go up and down and try filming that without tracking the subject.
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#10 Seth Melnick

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Posted 19 January 2008 - 12:04 AM

I still disagree - for every frame rate the varicam records there is a different cadence to fit it in a 60P stream. As you ramp the frames the cadence changes. So while each individual frame is temporally correct for the frame rate you are set at - it is showing for different amounts of time to fit in the 60P stream. At times its a whole number - each frame twice for example - at other times the pulldown requires a candence like 2:3:2:3 - so if you ramp and record but then play back at 60P then the rhythm of the frames change so you will not get the smooth motion you think you would. Add to all this that 24 frames is the likely rate the film will be shown at and then all this extra thought and work with the frame rates is irrelevant.

I think more work should be put into realizing that 24 frames per second works for 99 percent of the films (action or not) that exist so should be just fine for nearly all projects
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#11 Bruce Greene

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Posted 19 January 2008 - 01:23 AM

What I am looking for is 24p in order to preserve the film look and avoid that 60p cheesy soap opera look. On the otherhand I have found that 24p is totally inadequate for fast action. I think that the Varicam offers a powerfull technology in that the framerate can be selected even on the fly. Most people use variable framerates as overcranking for slow motion but what most people do not realize is that variable frame rates can be played back in real time. Thus it is possible to select the exact framerate to coresspond with the motion while still preserving the film look.

Hi Thomas,

Yes, your idea will work as long as you capture and edit the Varicam footage at 60fps. If you want to keep the effect in a film out, you'll have to project the film at 60fps a la showscan.

So, you're not crazy...though I'm not sure that well lit and photographed 60fps movies (film or digital) look like "video"(or cheesy soap operas). After all, if one shoots a static landscape at 24fps it will look identical to shooting at 60fps when played back at 60fps (with added pulldown), yet it doesn't look any more or less "video". Personally I rather like the look of shooting and playing back at frame rates above 24fps. When we get to digital projection as the standard in theaters, we'll be able to choose our frame rates for each production I imagine.

-bruce
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#12 Michael Nash

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Posted 19 January 2008 - 02:20 PM

I still disagree ...

Add to all this that 24 frames is the likely rate the film will be shown at and then all this extra thought and work with the frame rates is irrelevant.


What I said (and I think what Thomas was suggesting) is that the footage would be displayed at 60fps, not 24.

Yes, some frame rates have "smoother" pulldown cadences than others when spread out to 60fps, but during a ramp (especially if it's short enough), you may not notice it as much. The longer a "stuttery" pattern is on the screen, the more you notice it. During a single ramp it may not even be visible, depending on scene content.
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