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Old April 15th, 2003, 05:11 PM   #1
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Slo-motion?

Anyone have any advice or examples of 'attempted/simulated' slo motion that was filming with an XL1S?
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Old April 15th, 2003, 06:12 PM   #2
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Hello Frank,
Unlike film cameras, which can shoot certain film stocks at high frame rates, conventional video cameras like the XL1s can only shoot at 30 frames per second (NTSC). Therefore, the job of creating a slow-motion effect lies mainly with post-production techniques.

Certain editors, such as Final Cut Pro, can do a respectable job of altering a clip's speed within approximately 5%. For greater variations you'll need a specialty tool or plug-in such as Re:VisionFX's Twixtor. Such tools attempt to intelligently construct the additional frames necessary to create a slo-mo effect.

Addendum: I should add that, while shooting, you should use a somewhat higher shutter speed than normal. Something in the 1/80 - 1/100 range should be good for many subjects. Reason: you want to minimize motion blur to better enable such products to generate the additional frames.
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Old April 15th, 2003, 06:29 PM   #3
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Thank You.

I appreciate you taking the time to give advice.
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Old April 23rd, 2003, 10:30 AM   #4
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Besides Ken's excellent advise (do use higher shutter speeds)
also make sure you are recording in FRAME mode (or if that is
really not wanted/possible make sure you de-interlace the footage
first!!). Otherwise you will get into interlacing problems when
slowing the footage down!

Oh... and try it out before using it on a "real" production!!
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Old April 24th, 2003, 06:40 AM   #5
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Hi all,

Rob, my experience is quite the contrary, I find that attempting to slow down frame mode footage just looks really awful and very jerky. I find that much better results can be had by shooting normally (50i or 60i) and then slowing it down... if a final 24p, 25p, or 30p is desired, then to deinterlace in post or use something like Magic Bullet. Try it and see, I'm sure frame mode footage doesn't slow down well. But I agree about using a higher shutter speed though, that helps.

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Old April 25th, 2003, 07:43 AM   #6
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Hmmm.. interesting Adrian. I've always more or less assumed that.
I'll run some tests next week to see what happens! Thanks!!
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Old April 25th, 2003, 05:16 PM   #7
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yah, I think it probably has to do with the fact that with 50i or 60i, there are more intermediate 'steps' for the computer to do the inbetween interpolations compared with a 25p or 30p footage. Let me know the results of your tests!
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Old April 25th, 2003, 05:44 PM   #8
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I get good results slowing video down with Vegas 4, as long as I don't go under 55 or so percent. The only thing that bothers me, is I get flicker when its slowed down and viewed on at TV. Any advice on how to get rid of that with Vegas?
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Old April 25th, 2003, 05:49 PM   #9
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that is my experience as well, if i attempt to slow down frame mode footage, the result is jerky and it flickers. shoot 'normal', slow it down and see the difference.
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Old April 26th, 2003, 06:13 PM   #10
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A really easy and fairly high quality lethod for this is to shoot 50i (or 60i of course), then extract individual fields to frames doubling them in height, effectively doubling the framerate to 50p or 60p depending on source material. Now you re-adjust the framerate back to 25p and you're set for pretty good slomo. VirtualDub is pretty good at this, you can do it in Premiere/Xpress DV too but it's more cumbersome. Dunno about Vegas, maybe someone can chip in...
Have a read thru http://shelob.mordor.net/dgraft/bob.html for more information on how to do this.

HTH,

Kai.
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Old April 27th, 2003, 03:45 AM   #11
 
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I've done what Kai has suggested in Final Cut Pro. The results are indeed very smooth. I cannot remember the teqnique I used to do this, but I am about to start a project where I must do it again, so I'll figure it out.

**scratches head** I think maybe I deinterlaced once for ODD FIELDS and exported as individual frames in a folder, then did the same for the even fields, and then combined them all back into a movie.... nahhhh there had to have been an easier way.
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Old April 28th, 2003, 10:01 AM   #12
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Curtis, I would be very interested to hear how you did this in FCP.

Thanks!
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Old April 29th, 2003, 02:45 AM   #13
 
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Just for fun I did exactly what I posted above and got great results. But then I took the original file (shot in 60i, NOT frame mode or whatnot) and slowed the speed to 50% in Final Cut Pro under the "Modify" menu. The reult is EXACTLY the same and takes about a billionth of the time and hassle. Just be sure to choose "blend frames", which is the default.

If you need to output to film than this is probably not the best solution. But then again if you wanna output to film, shoot on film!
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Old April 29th, 2003, 03:53 AM   #14
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true true, considering the cost of tape to film transfer ($50K to $100K for a feature), if you require output to film, then it might actually be cheaper shooting on film if you can maintain a reasonable shooting ratio.

back to topic:

Curtis, thanks for trying out the two methods of slowing down footage, I've been meaning to try out the method Kai suggested but have been too lazy, looks like I'll stick to the 'easy way'!
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Old April 30th, 2003, 01:42 PM   #15
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Don't forget that using that VirtualDub plugin you will get better results than using the simple blend frames method as the plugin cleverly scans your footage and only interpolates pixels where there is movement (i.e. change between fields in a pixel). This means that with little or no movement in the picture, you will effectively get the full resolution of your footage with no interpolation at all, so 1.4 times the perceived resolution of the FCP blending method (assuming a quad interpolation) - noticable by any standard!
As soon as your camera is doing any kind of panning you're SOL with that method though, and the VDub plugin will do the exact same as the FCP process described above.

Kai.
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