picture jitter using cineframe 25 at DVinfo.net

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Sony HVR-Z1 / HDR-FX1
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Old July 12th, 2008, 08:45 PM   #1
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picture jitter using cineframe 25

Hello! I've been shooting street scenes for a video sequence and have turned on the Cineframe 25 (in the FX-1E PAL version). Everything looks real nice, but shooting out on a busy street means traffic whizzing by across the frame - and with the cineframe turned on there's a lot of jittering (or whatever its called). Is there any way to smooth out this jitter in post? I don't want to shoot in normal video mode, the 25 fps feel is real cool as long as things move slowly and smoothly - but for those street scenes I'm pretty much in trouble! Help!
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Old July 13th, 2008, 12:33 AM   #2
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Ali.


For 24P or 25P, this is the normal condition even with real motion picture film.

With film cameras, the shutter speed is generally about twice the frame rate, sometimes a little higher but not by much.

That shutter speed is in the ballpark of 1/50th - 1/60th of a second.

It so happens that this shutter speed causes movement across the image frame to become blurred much to the same degree that the human eye blurs fast movements.

This is sometimes referred to as the motion signature of film.

There is a zone of movement speed from very slow to moderately fast, which on motion film looks plain ugly. Jitter or judder are the words used to describe it.

It is apparent at its ugliest with pan follows of a moving subject or tracking shots of a moving subject, or as you have discovered, background objects moving moderately fast across the image, but not fast enough to become blurred.

Experienced cinematographers might intuitively avoid those shots altogether or adjust them when setting up.

They might use lenses and compose their shots to make the motion slower and less apparent ( a wider angle lens maybe ) or faster, ( using a longer lens ) to blur out the background significantly with selective focus and cause the relative movement of the background object across the frame to be faster and motion blurred.

The director might choreograph the movement of the subject to avoid the problem or just choose to live with it. In "Saving Private Ryan", this artifact was actually chosen for creative purposes by the use of modified shutter disks to replicate the higher shutter speed of some of the cameras used in the field at that time.

Modern video camcorders with 1/3" or smaller image pickups (CCDs, CMOS, "chips") or whatever people want to call them, do not see the world as film cameras do.

It is much harder to use selective focus as small format video camcorders have a very deep natural depth-of-field and everything from close to far away in the image looks sharper.

The only choices you have are to keep the shutter speed at about 1/50th of a second by using manual settings and to sit off from the subject and use the zoom lens at a longer focal length which enables you more focus separation of the subject from the background.

A wider iris in manual settings also enables more focus separation. You may have to use ND2 or even add a ND filter in front of the camcorder lens to keep the light level down in the bright conditions you experience over there in your dry season.

There are more qualified people than I to advise on this subject, so take more notice of their comments.


EDIT:

On re-reading your message I discover I have missed the point entirely. Frame-blending may work. There is an article here on dvinfo about replicating the motion signature of film but this applies to interlaced vision. Sorry to have gone so far off-topic.

Last edited by Bob Hart; July 13th, 2008 at 12:45 AM. Reason: errors
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Old July 13th, 2008, 12:33 PM   #3
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A better idea:

Don't ever use the cineframe function of the Z1U. It irretrievably ruins the video, IMO.

You are better off shooting in standard 30i and then using a plug in to convert to 24p in editing, if that is the look you're going for.

Of all the things the Z1 does well, 24-frame video is not one of them.
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Old July 14th, 2008, 12:22 AM   #4
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He is using a PAL camera with Cineframe 25 which is not quite as vicious as Cineframe 24.

However I otherwise agree with you. It is better to have the purest original image as you can always come back to it if adjustments do not work out later in post.

I have used Cineform's products starting from AspectHD to ProspectHD and to my own eyes at least, this seems to do a better job of converting interlace to progressive, so I do not use the Cineframe setting.

Last edited by Bob Hart; July 14th, 2008 at 12:22 AM. Reason: error
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Old July 14th, 2008, 04:53 AM   #5
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frame blending on progressive?

Hi, thanks for all your input. So since I'm stuck with the Cineframe 25 (PAL) judder (jitter?) is there any software or plugin or technique that'll smoothen out the footage? I wish I had posted this BEFORE I actually went out and shot everything in CineFrame25. Oh well, any help at this stage would be highly appreciated.
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Old July 15th, 2008, 11:23 AM   #6
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Other than looking for a temporal up-sampler, there's not much you can do.

I for one like shooting in Cineframe modes on my FX1. The post process doesn't require a computationally expensive deinterlace step, and you don't have to deal with spatially separated chroma information.

-Steve
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