I'm shooting a music video and am going for that slow motion look with real time vocals and accompanying music. I will be shooting on a canon xh-a1 and I'm not sure what frame rate to shoot on and how I should go about speeding up the song I have. I have to Pro-Tools session, but, as far as I can tell, there is no way to speed it up in there. I know I can do it in FCP, but it isn't precise enough. For example, when I set it to 250%, it actually sets it to 250.08% Which i presume could be very problematic. So if I end up shooting in 60i, and slow down to 24p, how fast should I speed the song up? Thank you for your help.
Slow motion looking music video
- Thread starter Ianb123
- Start date
unclebob6958
Well-known member
Pro Tools has a time stretch function (TCE - Time Compress/Expand). You'll just have to pull out the calculator and figure out the exact ratios and experiment a bit before the shoot.
SMuir
Well-known member
If you're shooting with NTSC gear, 60i actually works out to 59.94 fields per second. If you're posting in 24p video, your actual framerate is likely going to be 23.976, which you'll want to take into account in your calculations.
That works out to a time compression/expansion ratio of 0.4:1
To be on the safe side, shoot a test going the opposite direction: rolling at 60i, snap a slate, continue shooting through the duration of the song, then snap a tail-slate. Capture the footage at 60i, and import the sound track directly into Pro Tools. Run a TC/E operation on the soundtrack with a ratio of 2.5:1 and export that into a format that you're NLE likes. Back in the NLE, convert the 60i footage to 24p to get it into slow motion, and import the time-expanded version of the audio. If you can get both of the slates to match up without drifting, then your in business: just time-compress the music by 0.4:1 and use that for playback on-set.
That works out to a time compression/expansion ratio of 0.4:1
To be on the safe side, shoot a test going the opposite direction: rolling at 60i, snap a slate, continue shooting through the duration of the song, then snap a tail-slate. Capture the footage at 60i, and import the sound track directly into Pro Tools. Run a TC/E operation on the soundtrack with a ratio of 2.5:1 and export that into a format that you're NLE likes. Back in the NLE, convert the 60i footage to 24p to get it into slow motion, and import the time-expanded version of the audio. If you can get both of the slates to match up without drifting, then your in business: just time-compress the music by 0.4:1 and use that for playback on-set.
Article by Barry Green
The problem with giving exact answers is that the frame rates aren't exact, so even if someone comes in with the magic formula it'll still have to be tested to be sure.
But, with that said, the basic formula is that you first want to determine your footage playback speed, and once you know that, it tells you how to modify the song. So (in theory) if you're wanting to shoot 48fps slow motion for a 24fps timeline, you'd be getting 2:1 slow motion, so you'd have to speed up the song so that it plays for exactly half as much time as normal.
So again, in theory, you'd take a four-minute song and speed it up so that it plays for exactly two minutes. Then you'd set the HVX into 24pN mode, set your frame rate to 48, and play the sped-up song and have your actor/singer lip-sync to the super-fast version of the song. Then when you play your footage back it'll be in 2:1 slow motion, and you'd marry that version of the footage to your original song, and they should now be in perfect sync.
But they won't be. Because there's theory, and there's this troubling thing called "reality," and the reality here is that the frame rates are not what they say they are. 24fps is not, for example, 24fps; it's 23.976. And 48fps is not 48, nor is it 47.952 (as you might think, if it's twice as fast as 23.976)! It isn't. It's actually 48.17. And 12fps isn't 11.988, it's 12.26. Except if you're on the PAL HVX, where it actually is 12.500, half of 25.000.
So you need to adapt the formula to comply to the actual frame rates. Fortunately the HVX does part of that work for you, by doing the 24pN (or 25pN) conversion in-camera, so we only have to concern ourselves with how much to speed up the song by.
I haven't tested these, but I'd guess they're accurate; if anyone tests them and finds them inaccurate please let us know.
For an NTSC/US HVX, using a 24p timebase, for the following frame rates, adjust the song speed to:
12 fps: make song last 1.956x longer by stretching it to 51.1% speed
18 fps: make song last 1.333x longer by stretching it to 75.0% speed
20 fps: make song last 1.226x longer by stretching it to 81.6% speed
22 fps: make song last 1.067x longer by stretching it to 93.7% speed
26 fps: make song last 0.907x as long as normal; play it at 110.25% speed
30 fps: make song last 0.800x as long as normal; play it at 125% speed
32 fps: make song last 0.747x as long as normal; play it at 133.87% speed
36 fps: make song last 0.672x as long as normal; play it at 148.81% speed
48 fps: make song last 0.498x as long as normal; play it at 200.80% speed
60 fps: make song last 0.400x as long as normal; play it at 250.00% speed
For an NTSC/US HVX, using a 30p timebase, for the following frame rates, adjust the song speed to:
12 fps: make song last 2.445x longer by stretching it to 40.91% speed
18 fps: make song last 1.667x longer by stretching it to 60.00% speed
20 fps: make song last 1.533x longer by stretching it to 65.23% speed
22 fps: make song last 1.333x longer by stretching it to 75.01% speed
24 fps: make song last 1.250x as long as normal; play it at 80.00% speed
26 fps: make song last 1.134x as long as normal; play it at 88.22% speed
32 fps: make song last 0.933x as long as normal; play it at 107.14% speed
36 fps: make song last 0.840x as long as normal; play it at 119.05% speed
48 fps: make song last 0.622x as long as normal; play it at 160.73% speed
60 fps: make song last 0.500x as long as normal; play it at 200.00% speed
For the Euro/PAL camera it's different; the timebase of PAL footage is 25.000 fps, so that makes it easier. But the other frame rates may vary, so it needs some calculation too.
For the PAL/EU/AUS/NZ cam, set the recording mode to 720/25pN, then set your frame rate to whichever your chosen fps is. Then adjust the speed of the song according to this table:
12 fps: make song last 2.000x as long as normal; play it at 50.00% speed
18 fps: make song last 1.400x as long as normal; play it at 71.44% speed
20 fps: make song last 1.266x as long as normal; play it at 78.96% speed
23 fps: make song last 1.080x as long as normal; play it at 92.60% speed
27 fps: make song last 0.920x as long as normal; play it at 108.68% speed
30 fps: make song last 0.840x as long as normal; play it at 119.04% speed
32 fps: make song last 0.778x as long as normal; play it at 128.56% speed
37 fps: make song last 0.680x as long as normal; play it at 147.04% speed
48 fps: make song last 0.520x as long as normal; play it at 192.32% speed
50 fps: make song last 0.500x as long as normal; play it at 200.00% speed
The problem with giving exact answers is that the frame rates aren't exact, so even if someone comes in with the magic formula it'll still have to be tested to be sure.
But, with that said, the basic formula is that you first want to determine your footage playback speed, and once you know that, it tells you how to modify the song. So (in theory) if you're wanting to shoot 48fps slow motion for a 24fps timeline, you'd be getting 2:1 slow motion, so you'd have to speed up the song so that it plays for exactly half as much time as normal.
So again, in theory, you'd take a four-minute song and speed it up so that it plays for exactly two minutes. Then you'd set the HVX into 24pN mode, set your frame rate to 48, and play the sped-up song and have your actor/singer lip-sync to the super-fast version of the song. Then when you play your footage back it'll be in 2:1 slow motion, and you'd marry that version of the footage to your original song, and they should now be in perfect sync.
But they won't be. Because there's theory, and there's this troubling thing called "reality," and the reality here is that the frame rates are not what they say they are. 24fps is not, for example, 24fps; it's 23.976. And 48fps is not 48, nor is it 47.952 (as you might think, if it's twice as fast as 23.976)! It isn't. It's actually 48.17. And 12fps isn't 11.988, it's 12.26. Except if you're on the PAL HVX, where it actually is 12.500, half of 25.000.
So you need to adapt the formula to comply to the actual frame rates. Fortunately the HVX does part of that work for you, by doing the 24pN (or 25pN) conversion in-camera, so we only have to concern ourselves with how much to speed up the song by.
I haven't tested these, but I'd guess they're accurate; if anyone tests them and finds them inaccurate please let us know.
For an NTSC/US HVX, using a 24p timebase, for the following frame rates, adjust the song speed to:
12 fps: make song last 1.956x longer by stretching it to 51.1% speed
18 fps: make song last 1.333x longer by stretching it to 75.0% speed
20 fps: make song last 1.226x longer by stretching it to 81.6% speed
22 fps: make song last 1.067x longer by stretching it to 93.7% speed
26 fps: make song last 0.907x as long as normal; play it at 110.25% speed
30 fps: make song last 0.800x as long as normal; play it at 125% speed
32 fps: make song last 0.747x as long as normal; play it at 133.87% speed
36 fps: make song last 0.672x as long as normal; play it at 148.81% speed
48 fps: make song last 0.498x as long as normal; play it at 200.80% speed
60 fps: make song last 0.400x as long as normal; play it at 250.00% speed
For an NTSC/US HVX, using a 30p timebase, for the following frame rates, adjust the song speed to:
12 fps: make song last 2.445x longer by stretching it to 40.91% speed
18 fps: make song last 1.667x longer by stretching it to 60.00% speed
20 fps: make song last 1.533x longer by stretching it to 65.23% speed
22 fps: make song last 1.333x longer by stretching it to 75.01% speed
24 fps: make song last 1.250x as long as normal; play it at 80.00% speed
26 fps: make song last 1.134x as long as normal; play it at 88.22% speed
32 fps: make song last 0.933x as long as normal; play it at 107.14% speed
36 fps: make song last 0.840x as long as normal; play it at 119.05% speed
48 fps: make song last 0.622x as long as normal; play it at 160.73% speed
60 fps: make song last 0.500x as long as normal; play it at 200.00% speed
For the Euro/PAL camera it's different; the timebase of PAL footage is 25.000 fps, so that makes it easier. But the other frame rates may vary, so it needs some calculation too.
For the PAL/EU/AUS/NZ cam, set the recording mode to 720/25pN, then set your frame rate to whichever your chosen fps is. Then adjust the speed of the song according to this table:
12 fps: make song last 2.000x as long as normal; play it at 50.00% speed
18 fps: make song last 1.400x as long as normal; play it at 71.44% speed
20 fps: make song last 1.266x as long as normal; play it at 78.96% speed
23 fps: make song last 1.080x as long as normal; play it at 92.60% speed
27 fps: make song last 0.920x as long as normal; play it at 108.68% speed
30 fps: make song last 0.840x as long as normal; play it at 119.04% speed
32 fps: make song last 0.778x as long as normal; play it at 128.56% speed
37 fps: make song last 0.680x as long as normal; play it at 147.04% speed
48 fps: make song last 0.520x as long as normal; play it at 192.32% speed
50 fps: make song last 0.500x as long as normal; play it at 200.00% speed
AnnaCarrington
New member
In reply to Barry Green - I think you've got your maths wrong. You seem to be rounding some numbers in your equation and are therefore not getting accurate results. For PAL countries where shooting is usually 25fps the easiest way to do the maths is just take the FPS you want to shoot for slow motion/fast motion and divide by 25. So 37fps divided by 25 = 148% speed not 147.04 as stated in your post.
Anna Carrington
Director of Photography
UK
www.annacarrington.co.uk
Anna Carrington
Director of Photography
UK
www.annacarrington.co.uk
Andrius Simutis
Veteran
All the science and math aside, you should really be concerned about the lip synch. It's hard enough for a lot of performers to lip synch to their own songs at regular speed, and it's really hard for them to do it at half speed, and really really really hard for them to do it at double speed! Once you've done some tests and figured out the correct speed, give the band their song sped up to the speed that it will be played back while shooting. Have them practice it a lot. And then practice it some more. In the edit, expect to use shorter clips than you imagine since even with practice they won't always nail that synch.
Michael Carter
Veteran
60p to 24p is just way, way too fast. Try speeding a track up and see what I mean... it's barely a "song" anymore...