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Old September 20th, 2008, 08:58 AM   #1
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Best Settings For Slow Motion?

hi guys.

how would you recommend shooting video that's going to be made slow-motion in post-production? what would be the best settings for that? shutter speed,etc... i mean, everything possible to achieve that smooth (as opposed to jerky) look. (i'd bring as an example the slow-motion chorus bit in James Blunt's music video "High" where he runs through a forest.)
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Old September 21st, 2008, 02:47 PM   #2
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Aram,

Here's the thing about slow motion.

If you shoot at a specific frame rate (say 30 fps video) - then turning that footage into "slow motion" is always a compromise because the original capture of information marched to a specific NOT slow motion drummer.

You have a picture every 30th of a second to work with. (Or if you're working with interlaced footage, half a picture every 15th of a second.)

If you're taping a fast moving object, that object may move significantly between two frames during that 30th or 15th of a second. Decreasing shutter speed gives you frames that are LESS clear, because the object you are shooting moved position during the time of the exposure. (motion blur)

Increasing shutter speed give you clearer frames because the quick shutter "froze" the object in time - but you get LESS of those frames to work with. A quick snapshot when the object is here. Then another quick snapshot when the object is there. No information in between.

There are software programs that do motion interpolation - essentially trying to INVENT frames between what the camera has shot, but that's pricy and inefficient.

If you REALLY want's the kind of slow motion that's truly fluid and natural, you MUST record additional information to fill in between the frames.

The idea has a simple name. It's called "overcranking" because back in the film days, that's precisely what they did. Cranked the film through the camera FASTER exposing more frames for a given period of real time.

Quite a few modern digital camcorders allow this kind of electronic overcranking - exposing more frames than are needed for simple real-time playback.

Get one of those if you want the kind of fluid slow motion you're discussing.

Anything else and you'll be very disappointed with the results.

Good luck.
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Old September 22nd, 2008, 03:37 PM   #3
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I'd read a bit about shooting footage at 60i (or some other faster-than-24fps rate), de-interlacing, then converting it frame-for-frame to 24p ( or 25p or 30p). Could likely similary convert 30p to 24p for a more suble slowmo.

I haven't yet owned a camera capable of 60i recording, so I couldn't tell you exactly how or how well any of this works.

As to how to capture the footage, just get the sharpest focus, most light, highest shutter speed you can manage, I'd reckon.
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Old September 23rd, 2008, 08:55 AM   #4
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RAREVISION - New Media & Broadcast

Everything you could possibly need to digital cinema slow mo in the above link! Infact, sticky the link someone, it's ever so useful.
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Old September 23rd, 2008, 09:44 AM   #5
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Quote:
Originally Posted by Bill Davis View Post

You have a picture every 30th of a second to work with. (Or if you're working with interlaced footage, half a picture every 15th of a second.)

If you're taping a fast moving object, that object may move significantly between two frames during that 30th or 15th of a second.
If it's NTSC and the shutter speed's set at the default 1/60th sec then you're shooting 30 fps and 60 half-resolution frames per second and effectively capturing everything that happens in front of your camera. If you shoot at 1/120th sec you capture half of everything that happens and so on.

Obviously slo-mo 'drags-out' real time, so the more info you give it, the better the job (generally) it will do. So stick to 1/60th sec shutter speed (or 1/50th in PAL). Certainly don't go for the highest shutter speed as Kevin (who doesn't have avideo camera) recommends.

tom.
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Old September 25th, 2008, 03:04 PM   #6
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After reading this thread I experimented with some archived footage that I have of a pelican in flight. The original footage was fairly tight on the pelican and he nearly filled the frame. It was shot on a V1 in 1080/60i mode with the standard shutter speed of 60 fps. I put in into Premier Pro CS3. I slowed it to 20% (1/5th of the original speed). Without any further tweeking, fiddleing or manipulation the footage looked amazing, IMHO. No stutters. No jittery motion. No funny artifacts. Nothing. You could see the feathers on the tips of the wings and they exhibit some beautiful motion blurring. And you could also see the drops of water falling off of his feet, trailing behind him as he gained speed.
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Old September 26th, 2008, 02:14 AM   #7
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Excellent Greg. And you've proved that slo-mo loves to be fed as much info as possible before it starts its interpolation. You say, '1080/60i mode with the standard shutter speed of 60 fps.' but I'm sure you mean 1/60th sec as you're still shooting 30fps.

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Old September 26th, 2008, 05:38 PM   #8
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Ooops, yeah that is what I meant. Dooh.
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Old September 26th, 2008, 10:22 PM   #9
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At the risk of sounding a pink note in all this, I'm going to disagree. Conventional wisdom states that you want to shoot at a faster shutter speed to get each frame with as clean an image as possible.

If you're shooting with a still camera you know you'll get a cleaner action shot with a shutter at 1/125 or 1/250 than you will at 1/60. Same logic applies here. Cleaner images will give you better footage to work with if you end up using software that will interpolate motion.

After Effects has a tool that will do this and it does a good job (in most cases, but not all). If you feed it blurry images you'll end up with some nasty artifacts.

To contradict myself, you can get good slomo at 60i at 1/60. I used Premier Pro's Time Remapping to slow some race footage to 50% speed, which I think came out well. You can judge for yourself by watching it here: On Pit Lane-Episode 5 on Vimeo. The slomo is right at the beginning. There are also some slomo and time remapping sequences in the "Eye Candy" section at the end. These were shot at 1/250. I don't know if you can see a big difference in the quality, and it's a bit of an "apples and armadillos" comparison because of the vast difference in the lighting conditions but you can draw your own assessments.

Last edited by Tripp Woelfel; September 26th, 2008 at 10:36 PM. Reason: Added comment about TR at end of Vimeo clip
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Old September 27th, 2008, 06:00 AM   #10
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Tripp, while reading your post, it occured to me that maybe another way to look at this is that one reason cartoon characters never used to look "right" was the lack of motion blurring. The were a collection of very crisp images. Like you would get if you were shooting at extremely high shutter speeds. People that are filmed at typical shutter speeds look sharp when viewed normally, but if you examine each frame in detail, there is actually a very slight bit of motion blurring that makes it look "better". If your computor interplolates the additional frames to fill the spaces, does it introduce natural motion blurring or does it interpolate a series of crisp frames, which might not look as natural? I don't know. Does that make sense?
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Old September 27th, 2008, 09:19 AM   #11
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Greg... Your point absolutely makes sense, and Premier Pro will automatically blend consecutive frames when slowing the footage down. It's not motion blur per se, but the effect is similar.

The After Effects speed tool (can't remember the name of it) that creates slow motion footage will actually interpolate motion and can have motion blur applied to it.
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