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Speed Ramping w/ the Sony HDW-F900 Cinealta


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#1 Cole Webley

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Posted 12 February 2007 - 03:01 PM

Does anyone know how to do speed ramping in camera with the F900 or what equipment I would need to rent to do it? I am just learning this camera and the director wants to do some ramping...is it even possible in camera with this guy or should we shoot those shots on film and/or shoot the HD highspeed and then do it in post?

Help!

Thanks
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#2 Michael Nash

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Posted 12 February 2007 - 06:36 PM

Unless there's some very recent development I'm unaware of (which is possible), I don't believe you can do any kind of speed ramping in-camera with the F-900. It records 24P, 25P, 30P, 50i and 60i only, and you can't change frame rates while recording. You would have to pick one speed for the shot you want to ramp, and decide how you want to affect the speed change in post. At 60i you're obviously losing some resolution if you're trying to create 60fps out of it, but it has been done with pretty good-looking results. I'm not sure exactly what it entails in post, though.

The SRW-1 HDCAM-SR deck will record a 1080/60P signal at 4:2:2, but I'm not sure if you can shoot this speed with the 900 or if you need the 950 model. Never done that before. In any case, that still only gives you the option to shoot the desired scene at 60P, then you'd still have to create the ramp in post.

With the Panasonic Varicam you can change the frame rate while recording, but not a smooth ramp (again, unless there's a newer development I'm unaware of). And in any case, that still doesn't allow you control over the exposure change.
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#3 Cole Webley

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Posted 13 February 2007 - 03:37 PM

Thanks alot Micheal. I will be shooting tests next week...perhaps I can post them. Best of luck.
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#4 Matt Irwin

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Posted 13 February 2007 - 04:24 PM

You could test a higher shutter speed / angle- like 1/250 instead of 1/48- and then do the ramp in post. This would help to minimize the stutter that often occurs with artificial slo-mo.
I've done this before in SD with good results, but not with an F900.

Converting 60i to 60p might be smoother, but as Michael said, you would lose resolution.
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#5 Cole Webley

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Posted 16 February 2007 - 02:22 AM

Thanks Matt,

Next week I will have the camera for some tests and I will try both...shooting at 60i and also the higher shutter speed....what about a combination of both? I know I would have to have quite a bit more light but what kind of results do you think I would get if i shot a really higher shutter speed at 60i?

First time user of this camera...

Thanks
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#6 Michael Nash

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Posted 16 February 2007 - 05:13 AM

Thanks Matt,

Next week I will have the camera for some tests and I will try both...shooting at 60i and also the higher shutter speed....what about a combination of both? I know I would have to have quite a bit more light but what kind of results do you think I would get if i shot a really higher shutter speed at 60i?


To create 60fps slomo from 60i material you take each field and turn it into a complete frame, through some kind of line doubling or interpolation. Keep in mind that when shooting interlaced (60i), the shutterspeed applies to each field, not the frame. In other words a shutterspeed of 1/60 sec. exposes each field at 1/60 sec., not each frame at that duration. Someone correct me if I'm wrong on that; that's how I've always understood video.

So if you wanted to replicate the motion blur you would get with 60fps film with a 180 degree shutter, you would shoot with a shutterspeed of 1/120 second. Anything faster than that and it would be akin to shooting film with a narrow shutter angle (stroby motion); anything slower and you'd get more motion blur per field than you would normally get with a film camera with a 180 degree shutter angle.

In my opinion slower shutterspeeds on video are what give it a "video" look. If you want motion to appear as much like film as possible, stick to the equivalent of a 180 degree shutter or even smaller.
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#7 Cole Webley

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Posted 18 February 2007 - 12:14 PM

ok, makes sense. thanka
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#8 Michael Nash

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Posted 21 February 2007 - 12:48 AM

With the Panasonic Varicam you can change the frame rate while recording, but not a smooth ramp (again, unless there's a newer development I'm unaware of). And in any case, that still doesn't allow you control over the exposure change.


Ran across a potentially better method:
http://www.jkor.com/...eedramping.html
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#9 Cole Webley

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Posted 21 February 2007 - 11:57 AM

To create 60fps slomo from 60i material you take each field and turn it into a complete frame, through some kind of line doubling or interpolation.


How does this work?
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#10 Michael Nash

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Posted 22 February 2007 - 02:22 AM

How does this work?


It depends on the post technique used (several types of software can do it).

Here are some links:
http://broadcastengi...s_overcranking/

http://www.cinematog...osionsIn24P.htm

http://www.cinematog...onOutTo35mm.htm

http://www.hd-cinema.com/hd24p.htm
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#11 Will Earl

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Posted 22 February 2007 - 06:27 AM

How does this work?


Line doubling takes each the upper field and duplicates it to the lower field creating the first full frame image, it then takes the lower field and duplicates it to the upper field creating a second full frame image. This causes a loss in vertical resolution.

I've started to put some info up about retiming here... hopefully it shows what interpolation is doing.

http://www.earlyworm...hd/retiming.htm
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#12 Tony Yates

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Posted 22 February 2007 - 02:51 PM

Unless there's some very recent development I'm unaware of (which is possible), I don't believe you can do any kind of speed ramping in-camera with the F-900. It records 24P, 25P, 30P, 50i and 60i only, and you can't change frame rates while recording. You would have to pick one speed for the shot you want to ramp, and decide how you want to affect the speed change in post. At 60i you're obviously losing some resolution if you're trying to create 60fps out of it, but it has been done with pretty good-looking results. I'm not sure exactly what it entails in post, though.

The SRW-1 HDCAM-SR deck will record a 1080/60P signal at 4:2:2, but I'm not sure if you can shoot this speed with the 900 or if you need the 950 model. Never done that before. In any case, that still only gives you the option to shoot the desired scene at 60P, then you'd still have to create the ramp in post.

With the Panasonic Varicam you can change the frame rate while recording, but not a smooth ramp (again, unless there's a newer development I'm unaware of). And in any case, that still doesn't allow you control over the exposure change.


hi Michael
on a similar question to this thread I need to shoot slow motion (not ramped) on green screen (about the equivalent of 100fps has been requested) and am using the SRW-1 HDCam SR deck to record onto. Any advice on choice of capture camera bearing in mind I want to get as much color information and record 6op and push the slo mo in post ?
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#13 Michael Nash

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Posted 22 February 2007 - 06:57 PM

hi Michael
on a similar question to this thread I need to shoot slow motion (not ramped) on green screen (about the equivalent of 100fps has been requested) and am using the SRW-1 HDCam SR deck to record onto. Any advice on choice of capture camera bearing in mind I want to get as much color information and record 6op and push the slo mo in post ?


That gets a little out of my experience, so I'll tell you what I can and pass the buck to someone else...

From what I understand, HDCAM SR only supports 4:2:2 when it's 60P.

I think you might want to take a look at the Phantom: http://www.photonics...p;VNETCOOKIE=NO

There was some discussion on CML 2K-444 about using the Viper to create 120fps:
http://ls.cinematogr...sages?id=124528
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#14 Cole Webley

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Posted 22 February 2007 - 09:29 PM

Maybe I should start a new thread for this but I am wondering if anyone knows how to get the CineAlta to shoot at 6fps? I know there are ways to do this on the HVX-200 (saving scene files on the SD card) but does anyone know how to get this done on the CineAlta?

thanks!
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#15 Tony Yates

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Posted 23 February 2007 - 06:44 AM

That gets a little out of my experience, so I'll tell you what I can and pass the buck to someone else...

From what I understand, HDCAM SR only supports 4:2:2 when it's 60P.

I think you might want to take a look at the Phantom: http://www.photonics...p;VNETCOOKIE=NO

There was some discussion on CML 2K-444 about using the Viper to create 120fps:
http://ls.cinematogr...sages?id=124528



Thanks for that. I've used the phantom but didnt like the results. To be honest I'm leaning more and more towards trying to get them to shoot on film
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#16 Michael Nash

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Posted 23 February 2007 - 05:18 PM

Thanks for that. I've used the phantom but didnt like the results.


What was it about the Phantom you didn't like (just curious)?

Maybe I should start a new thread for this but I am wondering if anyone knows how to get the CineAlta to shoot at 6fps? I know there are ways to do this on the HVX-200 (saving scene files on the SD card) but does anyone know how to get this done on the CineAlta?

thanks!


Apparently there is an optional board (HKDW-905R) for the F900R that allows for slow shutter exposures, ranging from 1-64 frame accumulations (in certain increments). In other words, shutterspeeds of 1/24 to 2.6 seconds. So I'm guessing a 2-frame accumulation (1/12) played back at 400% in post would give you the correct motion blur and speed; or a 4-frame accumulation (1/6) played normally would look like 6fps step printed to 24, but with more motion blur.

http://www.pci-canada.com/HDWF900R.htm

The PDW F350 (XDCAM HD) supports 4-60fps recording, although with some compromises compared to the F900 (lower bit rate, 1/2" optics, different recording format/deck). It also has a slow shutter feature.

What's the trick for getting the HVX down to 6fps? I know you can do a 350 degree shutter at 12fps, but that's not the same...
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#17 Cole Webley

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Posted 23 February 2007 - 10:50 PM

What's the trick for getting the HVX down to 6fps? I know you can do a 350 degree shutter at 12fps, but that's not the same...



I was researching the how the HVX does it and someone sent me this thread, it explains how to do it...enjoy.

http://www.dvxuser.c...p;postcount=154
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#18 Michael Nash

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Posted 23 February 2007 - 11:26 PM

I was researching the how the HVX does it and someone sent me this thread, it explains how to do it...enjoy.

http://www.dvxuser.c...p;postcount=154


Awesome! Thanks!
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#19 Tony Yates

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Posted 24 February 2007 - 08:33 AM

[quote name='Michael Nash' date='Feb 23 2007, 02:18 PM' post='156700']
What was it about the Phantom you didn't like (just curious)?

Both the director and on line editor and myself thought the pictures lacked "bite" with a slightly soft feel.
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