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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old April 21st, 2007, 10:11 PM   #1
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XH-A1 and Slow Motion

Hi I'm very interested in the XH-A1 as a step up to my first HD camcorder from the Panasonic AG-DVC30. I've read a bit on the HDV format and the whole nine yards but I was wondering if there is anyone out there that has done some work with post production slow motion. I know ideally if you want crystal clear video and smooth play back under and over cranking is ideal but how is slow motion in post production with HDV video from the A1? Its not a major determining factor but the ability to utilize slower motion shots for post production work would be nice. Also fast action shots with the HDV format seems to catch some negative feedback. Any comment on this as well? Any other tips or info would be nice. Thanks for your time

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Old April 22nd, 2007, 01:43 AM   #2
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If you want smooth slomo without alot of fixing, shoot in 60i at as high of shutter speed as you could, and of course a good NLE program that can do good slomo.
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Old April 22nd, 2007, 02:25 AM   #3
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I've done some post work of various video shot with my XHA1. I use vegas 7.

Some tests I have done are dripping water into a bowl and slowing down the resulting drip/splash. When slowed down below 40% you start to notice the individual frames instead of fluid motion.

I also have slowed down whitewater kayaking on a standing wave. The video was slowed down to 46% and actually looks quite good. There is a lot going on in the scene in terms of movment (water moving, paddle, body) and it all looks very good.

I think it depends a little on what you are shooting and what you expect to slow things down to.

As for how to shoot it, there is a best case way to do so. I believe if you shoot 60i at 1/120 shutter speed you then create a progressive 60p video from this. Because the shutter speed is twice the camera frame rate the 60p footage will look very good. This 60p footage can then be slowed down with the highest quality results.

To use a higher than 1/120 shutter speed means you are possibly going to introduce a stuttered look to the resulting slowed down footage.
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Old April 22nd, 2007, 11:07 AM   #4
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Thanks so much for the quick responses. I'm really looking into this camcorder. Overall how do you feel about your A1 video at the end of post production and put back on an HDTV? The whole interlaced thing is kind of drawing me back but I can't afford the step up to the HVX200 with progressive scan. Any other stuff you would like to add would be wonderful. Thanks again for your time.
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Old April 22nd, 2007, 04:21 PM   #5
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Quote:
Originally Posted by James Hooey View Post
I've done some post work of various video shot with my XHA1. I use vegas 7.

Some tests I have done are dripping water into a bowl and slowing down the resulting drip/splash. When slowed down below 40% you start to notice the individual frames instead of fluid motion.

I also have slowed down whitewater kayaking on a standing wave. The video was slowed down to 46% and actually looks quite good. There is a lot going on in the scene in terms of movment (water moving, paddle, body) and it all looks very good.

I think it depends a little on what you are shooting and what you expect to slow things down to.

As for how to shoot it, there is a best case way to do so. I believe if you shoot 60i at 1/120 shutter speed you then create a progressive 60p video from this. Because the shutter speed is twice the camera frame rate the 60p footage will look very good. This 60p footage can then be slowed down with the highest quality results.

To use a higher than 1/120 shutter speed means you are possibly going to introduce a stuttered look to the resulting slowed down footage.
You can not get 60P from shooting 1/120 shutter speed, higher shutter speed will give you clearer slomo instead of more blur, your info. is wrong.
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Old April 22nd, 2007, 09:08 PM   #6
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Khoi, I'll explain the process a little more fully....

You shoot 60i video at 1/120 shutter speed. You then take this video and re-render it as a double ntsc frame rate 59.940 as a progressive scan video file and interpolate the fields together as well.

So...the theory is that since there are two shutter clocks for each full frame in the original 60i video, one for each field..... after rendering as above there will be one full frame for the 60p video that you create.

This 60p video is now more readily slowed down with a smooth look to it.

This is what I have gathered from various posts within DVinfo...or at least my understanding of them. Do a search about slow mo.

With higher shutter speed you may get "clearer" slow mo...that is each acutally video frame would have less smear in it, but there will also be more discrete movment from frame to frame so the video can depending on the situation looking a little more jumpy.

Again, this is my understanding from other posts and don't take my advice for more than it's worth...if someone of more knowledge has some advice I'd love to hear it.
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Old April 22nd, 2007, 09:46 PM   #7
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Hi James,

A few questions of you don't mind -

What process to you undertake in order to convert the 60i to 60p?

Do you simply render it in Vegas or do you apply some de-interlaced plug-in? Do you render it as an HDV file or with some intermediate codec?

Thanks,
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Old April 22nd, 2007, 10:55 PM   #8
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Quote:
Originally Posted by James Hooey View Post
Khoi, I'll explain the process a little more fully....

You shoot 60i video at 1/120 shutter speed. You then take this video and re-render it as a double ntsc frame rate 59.940 as a progressive scan video file and interpolate the fields together as well.

So...the theory is that since there are two shutter clocks for each full frame in the original 60i video, one for each field..... after rendering as above there will be one full frame for the 60p video that you create.

This 60p video is now more readily slowed down with a smooth look to it.

This is what I have gathered from various posts within DVinfo...or at least my understanding of them. Do a search about slow mo.

With higher shutter speed you may get "clearer" slow mo...that is each acutally video frame would have less smear in it, but there will also be more discrete movment from frame to frame so the video can depending on the situation looking a little more jumpy.

Again, this is my understanding from other posts and don't take my advice for more than it's worth...if someone of more knowledge has some advice I'd love to hear it.
Whatever you do, you still end up with "blend frame" and not true progressive frame, only camera that can record higher frame/second can deliver better slomo.
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Old April 23rd, 2007, 02:53 AM   #9
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The interpolation in Vegas from 60i to 60p (Or in my case 50i to 50p) is quite good. There are better applications out there but doing it in Vegas is simple.

Although Khoi is technically correct, I think you can achieve a perfectly acceptable image from interpolated footage for some things. What I have done is used a 25p timeline, taken the interpolated footage at '50p' and slowed it 50%. Looks okay. Particularly if you're taking HD footage and reducing it to SD.

Barry Green over on dvxuser has done demonstrations of this in SD and the technique is mentioned in his DVX book.

So, although technically Khoi is correct I find that people don't notice often the difference - I've even slowed 25p with frame blending in Vegas to 50% and everyone was happy with the result (Except me, it really was a bit blurry). It just depends what you're after. As long as you aren't expecting to achieve the same result as a true slomo where the footage has been taken at 120fps (or more) in true progressive and then slowed down, then IMHO you'll get by.
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Old April 23rd, 2007, 07:35 AM   #10
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There is no doubt that you can make slomo better, but on my original reply, I said, if you want good slomo without alot of fixing, you want to shoot in 60i, and not 24P or F, and some NLE will offer better slomo than the other, I'm talking about realtime, not rendering, not interpoled or frame blending...
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Old April 23rd, 2007, 08:47 AM   #11
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I'm happy with the slow-motion on the A1 compared to the the results I am used to getting from DV cams. I shoot everything at 60i and 1/60th of a shutter and other than fast panning, it seems to handle it well. Here is a clip we posted on our blog a week or so ago that has lots of slow-motion and some fast motion too, all shot with the A1 (the pics were a 5d though).

http://stillmotionblog.com/?p=51

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Old April 23rd, 2007, 12:23 PM   #12
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Quote:
Originally Posted by Patrick Moreau View Post
I'm happy with the slow-motion on the A1 compared to the the results I am used to getting from DV cams. I shoot everything at 60i and 1/60th of a shutter and other than fast panning, it seems to handle it well. Here is a clip we posted on our blog a week or so ago that has lots of slow-motion and some fast motion too, all shot with the A1 (the pics were a 5d though).

http://stillmotionblog.com/?p=51

Patrick
Hey Patrick,

Very nice. May I ask where you got the FLVPlayer Skin (the controls at the bottom of the video)? That is simple, clean and nice looking.. I'm looking for something like that that's a little better than the "stock" controls with Flash 8.
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Old April 23rd, 2007, 12:27 PM   #13
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It is a media center plug-in for wordpress. Thats exactly what its called. Not sure if it works outside of wordpress.

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Old April 23rd, 2007, 01:58 PM   #14
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wow patrick....that video is wonderful! What kind of stabilizer were you using with the A1 to get the smooth slow mo shots?
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Old April 23rd, 2007, 02:19 PM   #15
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Not to take the thread too far off topic but the clip was my first shoot with the Flyer. I'm getting better results now that I am getting more used to it. I had a Magiqcam for years and it offered roughly the same results as in the video, but at 20% of the price.
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