omino pixel blog
pixels, motion, and scripting
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david van brink // Thu 2007.10.25 22:38 // {after effects}
Synthetic Camera Motion
Canon HV20
Finally got a pretty decent video camera: a Canon HV20. Just came out earlier this year, and seems to be all the rage; lucky for me it was also what our little town of Santa Cruz had available on a moment’s notice, at Circuit City.
Nice enough. Not as macho as I’d prefer. I got spoiled borrowing a Canon GL2 from work (they use it to make really really bland training videos). This HV20 is tiny, and doesn’t have the overhead microphone/carry-handle and square sunshade of a real indie camera. Adding a gen-u-ine Canon wide angle adapter and accessory-shoe microphone (not a handle!) helps to bulk it up a little. Oh, and to shoot nicer video, too.
The menu system is all right; after a day or two of attention I learned all of it. You can override the focus and the exposure settings somewhat. It has a variable-speed zoom lever; a ring would be nicer.
24P
The HV20 records SD or HD video, apparently at a full 1920 by 1080, which is nice (for reasons I’ll demonstrate in an imminent post). It can record at either 30fps interlaced, or 24fps progressive. That’s cool.
(To recap — interlaced video is full of annoying horizontal stripes, and progressive isn’t. And 24 is the magic frame rate of real movies, so we take it as axiomatic that it’s “better” than 30 or 60 frames per second.)
Unfortunately, it doesn’t tag the firewire stream with the appropriate 24p markers, and applies a 3:2 pulldown automatically. And I read somewhere on the internetz that this was a specific choice by Canon because it’s a “consumer grade” product.
But! No matter. After Effects can fix it, trivially. Just capture the footage at full resolution. I used iMovie to capture, which works great. It offers a choice to capture at 960 by 540 half resolution; don’t do it!
Then import the footage to After Effects. Right click on the asset and choose the “Interpret Footage” menu item. Click the “Guess 3:2 Pulldown” button and ho ho! it doesn’t guess right every time, you may have to try all 10 combinations of upper/lower and five pulldown cadences.
And here are two QuickTimes showing the same footage as captured, and deinterlaced by After Effects 7.0.
24p in glorious 24p
24p with ugly 3:2
These were shot with a 1/1000th second shutter speed, at 33 1/3rd rpm. These movies show a tiny cropped area from the vast HD capture…
Try the QuickTime single step buttons (or left/right arrow keys) to see the difference between glorious 24fps and ugly, ugly 3:2 pulldown at 30fps. Glorious!
3 comments
Eugenia // Mon 2007.10.29 00:1412:14 am
The second footage is not ugly. You simply forgot to de-interlace before you export. If you had de-interlaced, it would have looked the same.
david van brink // Wed 2007.10.31 10:1810:18 am
Thanks for the pointer!
So… deinterlace on export? I’m not familiar, but it sounds like it would obtain the same result as deinterlace on import? I guess the key is to be sure to do one or the other?
My assumption was that you want to remove the pulldown as early as possible — on the interpret footage, right at the source — so that any further manipulation has flat frames.
The first ae comp is 24fps, with interpreted 24p footage,
The second ae comp is 30fps, with non-interpreted 60i footage — shot with the “24p” setting on the camera. The intent was to show how to extract the flat frames.
I’m still learning my way around the “video” aspects of ae.
Jonas Hummelstrand // Sun 2008.03.9 16:024:02 pm
No, no. David is correct, with the NTSC version of the HV-20 you need to remove the pulldown to get 24P. On the PAL version, you get 25P without all the hassles…
oh, i dont know. what do you think?
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Hello David. Iรยดm working exactly as you are and would just like to know how you animated that wide angle distortion when movind the cam. Can you tell me if it is it a plugin or a native AFX function? Today I only do rescaling and repositioning..
Hi Pedro — you will laugh when I tell you. I used a 3d layer, and the pan/zoom is done with camera angling. It’s kind-of strange looking… but in a different way than 2d pan/zoom. ๐
Hey David.
I saw your synthetic motion video on youtube over a year ago and I’ve been trying to emulate that for the longest time! I have an HV30 and After Effects CS3 as well.
I looked everywhere for a tutorial or a how-to video or anything without any luck so finally I thought I’ll ask the creator himself… If you can, please show us a video tutorial on how you did that? I’d really appreciate it. Thanks and keep up the good work ๐