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Old January 5th, 2007, 12:39 PM   #1
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Overcranked Slow-motion samples from HD200/250

Carl Hicks and Keith DeCristo sent me some 720P60 clips to play with recently. I've conformed them to 24P (23.98fps) to see the effects of overcranked slow-motion.

Here's a short segment of Keith's clip of some Kung Fu in either H264 Quicktime (11.3MB) or Windows Media (6.8MB).

Here's Carl's clip of a juggler in either H264 Quicktime (15.7MB) or Windows Media (9.3MB).

It looks like 1/60th shutter speed was used when at least 1/120th should be used for overcranked slow-mo. Even so, these clips clearly demonstrate that overcranking works very well.

I should also mention that Keith's clip came straight from a m2t captured on a DR-HD100, but Carl's had already gone through Premiere Pro 2 and had been re-encoded into m2t before I did anything to it. Therefore, there are some extra compression artifacts.
Here is Carl's original sample (49MB) that he had slowed down in Premiere to 50%. I noticed that the frames had been improperly interpolated so I took the first part and conformed it properly to 24P.

So how do you shoot your own slow-motion?

Here's the method on Apple MacOS X.
  1. Shoot some footage on a HD200 or HD250 in 720P60 (or 50). HD100/110 users can shoot standard definition 480P60 or 576P50.
    NOTE: If you are attempting to shoot 50P in North America with any type of flourescent source (KinoFlo) or gaseous lamp (sodium, mercury, metal halide, HMI,) you may have to set the variable shutter to around 1/60 or 1/120 to avoid flickering. (1/59.92 or 1/60.01) or (1/120.1 or 1/119.4) Square-wave HMI ballasts should cause no problems.
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  2. Capture an m2t with HDVxDV, LumiereHD, or Apple's DVHSCap/VirtualDVHS.
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  3. Open the m2t file in MPEG StreamClip. Cinema Tools can only conform the frame rate on quicktime I-frame based codecs, so we must transcode the m2t to quicktime.
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  4. Choose "Export to Quicktime" (⌘+E)
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    Overcranked Slow-motion samples from HD200/250-picture-1.jpg
  5. Set the compression to your desired I-frame based codec. I chose "FCP Uncompressed 8-bit 4:2:2" in this example, but if you would like to save hard drive space this method also works with Apple Intermediate Codec.
    I also selected "1280x720 (unscaled)" because this was already a 720P clip, but you can also use this feature in MPEG Streamclip to uprez your 480P60 or 576P50 files to 1280x720 (or 1920x1080 for that matter.)
    I also set the frame rate to 59.94, but you can leave it blank and the file should still default to its current frame rate.
    NOTE: It is important NOT to set the frame rate to 23.98 at this point. Doing so would create a 24P file that plays in realtime. This could be useful if you want to pull 24P out of a 60P file, but for our slow-motion purposes we will leave it at 60P.
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  6. Now Launch Cinema Tools and open (⌘+O) your new Quicktime file.
    NOTE:Hit Cancel if you are asked to open a Cinema Tools database during launch. This is normal.
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    Overcranked Slow-motion samples from HD200/250-picture-8.png
  7. Click the Conform button and set the frame rate to 23.98 (or 29.97 if you plan to work in 30P.)
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  8. Cinema Tools will instantly modify the quicktime file by simply telling it to play at the new frame rate. You will notice that the sample rate of your audio has been lowered by the same amount to maintain sync, so 48khz becomes 19.2khz.
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    Overcranked Slow-motion samples from HD200/250-picture-10.png
    You can now open the quicktime file and it plays in slowmotion. Cinema Tools has a little quirk that modifies the display size preference to 50%. Simply change this in the Quicktime Pro player to Actual size (⌘+1.)
    You can skip this step if you are going straight into FCP.

MPEG Streamclip has a batch export and Cinema Tools has a batch conform function if you need to process more than one clip at a time.
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Old January 6th, 2007, 05:25 PM   #2
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Quote:
Originally Posted by Tim Dashwood
Carl Hicks and Keith DeCristo sent me some 720P60 clips to play with recently. I've conformed them to 24P (23.98fps) to see the effects of overcranked slow-motion.

It looks like 1/60th shutter speed was used when at least 1/120th should be used for overcranked slow-mo. Even so, these clips clearly demonstrate that overcranking works very well.
I'm going to re-shoot using higher shutter speeds- I love the motion trails generated by the slower shutter speed, but it may not be ideal considering the target audience for this test. I'll try to keep the sequence within 15-20 seconds.

Tim, I hope I can bother you again to do some web encoding?
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Old January 6th, 2007, 05:31 PM   #3
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Tim,

Thanks for posting these. Almost doesn't look like slow motion. Its minimal. Would love to see something like running or other really fast motion, slowed down.
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Old January 6th, 2007, 05:41 PM   #4
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I have another question. Can I shoot a whole movie in 60P and edit it in 24p making some clips slow motion and others not? I use FCP5. I am shooting a small action short and some of it will be slowmotion, but to change camera from 24f to 60f on set between shots may be too time consuming.
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Old January 6th, 2007, 05:44 PM   #5
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How about posting the original m2t's please.
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Old January 6th, 2007, 07:24 PM   #6
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Quote:
Originally Posted by Brian Duke
I have another question. Can I shoot a whole movie in 60P and edit it in 24p making some clips slow motion and others not?
Yes, it is actually very easy to do this with Mpeg Streamclip.
You just need to enter 23.976 into the frame rate box when exporting to quicktime. Mpeg Streamclip will cherry-pick 24 frames out of the 60 and create a new file 24P quicktime. This is similar to a reverse telecine process from a 60i transfer, but of course the math is easier and the process is "dummy proof" because every one of the 60 frames is progressive.
You should test it out first and make sure sync is maintained with long clips. I tested this only on Keith's short clip.
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Old January 6th, 2007, 08:29 PM   #7
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Originally Posted by Brian Duke
Tim,

Thanks for posting these. Almost doesn't look like slow motion. Its minimal. Would love to see something like running or other really fast motion, slowed down.
I actually shot some running in 60P over a year ago. Here is the link:
http://homepage.mac.com/timdashwood/...lo-mo_test.mov
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Old January 6th, 2007, 08:33 PM   #8
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Originally Posted by Stephen L. Noe
How about posting the original m2t's please.
Here's the small bit of Keith's original m2t. I had to trim it to just a few seconds to make the download manageable.
Right-Click here - 13MB

I posted a link to the original m2t Carl sent me in the top post. Unfortunately, it isn't original straight from the camera, but had been through PP2. Carl is going to try to get the original clip for us.
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Old January 6th, 2007, 10:46 PM   #9
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Great clips, but for some reason the slo-mo didn't look as smooth and filmlike as expected or as smooth as the HVX200 60P footage. Was that because of the shutter speed? I have seen some very smooth SD60P footage with the HD100, and expected the same, but with higher resolution from the HD200/250.
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Old January 7th, 2007, 12:53 AM   #10
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Here is the type of slow motion rendition we've been getting from the HD-250. I've added a sample clip with slowed down footage, and on part of the clip I slowed down the audio as well to display how slow it really is. The first part is strobed on purpose.

The clip is 60p with the default shutter speed for 60fps and laid on a 29.97 timeline and then slowed 50%. I'm pleased with the motion rendition so far.

Click here for Windows Media HD

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Old January 7th, 2007, 04:45 AM   #11
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Originally Posted by Rogelio Salinas
Great clips, but for some reason the slo-mo didn't look as smooth and filmlike as expected or as smooth as the HVX200 60P footage.
How fast is your processor?

I can assure you that 720P60 clips, when slowed down properly, are as just as "smooth" as shooting 60fps on film or 60P on the HVX.

With that said, I tried playing the clips I posted on my Dual1.2Ghz G4 and I couldn't keep the frame rate constant. However, when I play these clips on a Duo2Ghz Macbook Pro they are as smooth as smooth can be.
H264 and WM HD need alot of processing horsepower, especially at the 6-8Mbps rates I used to compress them.
Quote:
Originally Posted by Rogelio Salinas
Was that because of the shutter speed? I have seen some very smooth SD60P footage with the HD100, and expected the same, but with higher resolution from the HD200/250.
The 1/60 shutter speed used is the equivalent of using a 1/24th shutter when shooting 24P, so the motion blur is unnaturally long. The shutter speed really should be above 1/120 to exactly mimic the look of overcranked film at 60fps.
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Old January 7th, 2007, 05:09 AM   #12
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Quote:
Originally Posted by Stephen L. Noe
Here is the type of slow motion rendition we've been getting from the HD-250. I've added a sample clip with slowed down footage, and on part of the clip I slowed down the audio as well to display how slow it really is. The first part is strobed on purpose.

The clip is 60p with the default shutter speed for 60fps and laid on a 29.97 timeline and then slowed 50%. I'm pleased with the motion rendition so far.

Click here for Windows Media HD

S.Noe
Stephen,

Would you mind sending me the original captured m2t of the shot where the gun drops? It looks like your NLE is interpolating the frames and I'd like to try the Mac process on it.
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Old January 7th, 2007, 05:10 AM   #13
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Originally Posted by Tim Dashwood
The shutter speed really should be above 1/120 to exactly mimic the look of overcranked film at 60fps.
Wouldn't that create a light issue, especially when I use my Mini35 which already lose 2 stops of light.

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Old January 7th, 2007, 06:31 AM   #14
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Originally Posted by Brian Duke
Wouldn't that create a light issue, especially when I use my Mini35 which already lose 2 stops of light.

Duke
Yes, by approximately an extra 1⅓ from 1/48th, but that is the price of hi-speed shooting. That's one of the reasons you see sets so "overlit" when the DP is planning to shoot high-speed.

Also, 60fps isn't really considered that fast when it comes to action movies. 60fps is the norm on most film cameras with a hi-speed capability.
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Old January 7th, 2007, 06:48 AM   #15
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Also, 60fps isn't really considered that fast when it comes to action movies.
I know. it didn't really seem that slow at all, considering I am going to shoot people flipping through air etc, I am not sure 60p will be slow enough. What to do? Slow it down in FCP?
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