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Old March 12th, 2007, 03:42 PM   #1
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Slow mo...

My brother has a JVC D340EK. We recently took it skiing and I have made a video of the holiday using Adobe Premiere Standard which came with my laptop. Some of the scenes I have put in slow motion using the "speed/duration" function at 50% of the original speed. This creates the right sort of speed but, when I play the movie back (after having rendered it) there is a flickering 'shadow' behind the people moving which makes the scene awkward to watch, this happens on both my laptop and the TV. When I play the film back in Adobe before rendering it there is nothing wrong with the footage. The only way to get rid of the flickering is to choose the de-interlace option when I render but this makes any moving titles judder as frames have been removed.

Is it the export settings I am using? They are: Microsoft DV AVI at 25fps with rendering options as "Fields: No fields (progressive scan)"
Or is it the way that I am applying the slow motion during editing?

Any help would be really appreciated as it is really bugging me.
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Old March 12th, 2007, 05:20 PM   #2
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Without seeing the footage it is hard to tell, but my guess is that the shutter speed was very high to compensate for the bright outdoor snow scene. High shutter speeds produce flicker that is expecially noticable in slow motion. My experience is that it is very hard to make this look good. If you have slow motion applied to darker scenes does it look as bad as the brighter scenes? Can you put the tape in the camera and see what the shutter speed was in the scenes that look bad?

If you have access to other programs that do slow motion better than Premiere such as Twixtor or After Effects you might want to try them on the slow mo scenes.

Hopefully others will have some solutions that will work for you.
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Old March 12th, 2007, 08:03 PM   #3
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Anyone interested in slow motion video should check out Goodervideo.com. They have software that interpolates frames between the actual frames to achieve very smooth motion. High shutter speeds may actually be beneficial for this software to reduce artifacts. The demo is free and the software is really cheap. The software only works on AVI files, so you would need to convert HDV to an AVI format.
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Old March 13th, 2007, 09:31 AM   #4
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Thanks for the advice, I'll give those a go. When I get home I'll check the shutter speeds, or is there a way to see it on the computer?
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Old March 13th, 2007, 11:40 AM   #5
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No, but you should be able to check your camera settings (assuming you haven't changed anything) to see what shutter speed you used.

At what point exactly in the workflow are you applying the titles?

De-interlacing is your friend, too.
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Old March 13th, 2007, 12:10 PM   #6
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I put the titles in whilst putting all the clips together, i.e I don't render the film then add the titles, do you think I should render and de-interlace then add the titles then re-render?
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Old March 13th, 2007, 06:52 PM   #7
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Definitely...de-interlace the footage and put the titles on top of that.
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Old March 14th, 2007, 06:41 AM   #8
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Great idea, don't know why I didn't think of that!
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Old March 18th, 2007, 05:38 PM   #9
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Quote:
When I get home I'll check the shutter speeds
I'm 99,9% sure that with this camcorder you don't have manual control over the shutter speeds. Better camcorders have built-in ND (neutral density) filters to reduce incoming light without using the shutter. Consumer camcorders usually don't have ND filters so the shutter is the only way to reduce light in bright situations. You can trick consumer camcorders by using screw-on ND filters (light is reduced before it comes in so the auto-shutter remains at 1/50, or at least somewhere near 1/50...)

A good value for an ND filter would be 1/8 (I think that translates to "ND9" or "0.9" or "8x" - so many terms for ND...) because that is the ND filter you will almost always use in daylight with professional camcorders. Unless it's really bright outside this should be enough to keep the shutter down. For really bright situations a 1/32 would be good.
This is by the way the ND-combo that the Panasonic AG-DVX100 uses, 1/8 and 1/32. Our shoulder mounts have 1/8 and 1/64, but I guess 1/64 would be too much ND for a consumer cam, even in very bright situations.
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