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Old August 11th, 2006, 05:24 PM   #1
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30p "shimmer" - am I doing something wrong?

I've been playing around with 480p30 and I notice a pronounced "shimmer" on several parts of the image (usually where bright areas meet dark areas, such as where light peeks through tree leaves). It is very evident in horizontal pans (and I'm being slow). Even in a non-moving shot I can see it in places. Is this normal? I also see stair stepping as well.

Isn't 30p supposed to look sharper than 60i? It doesn't look that way to my eyes, but this is a very unscientific observation.
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Old August 11th, 2006, 05:56 PM   #2
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Quote:
Originally Posted by Bill Edmunds
I've been playing around with 480p30 and I notice a pronounced "shimmer" on several parts of the image (usually where bright areas meet dark areas, such as where light peeks through tree leaves). It is very evident in horizontal pans (and I'm being slow). Even in a non-moving shot I can see it in places. Is this normal? I also see stair stepping as well.

Isn't 30p supposed to look sharper than 60i? It doesn't look that way to my eyes, but this is a very unscientific observation.
I can't comment on the shimmer, since I never shoot 480/30. Sadly, Avid doesn't yet support that frame rate, and I'm still not up to speed enough on FCP to switch over to it.

As for sharpness... nah. The signal coming off the CCD is virtually identical. The only difference (that I'm aware of) is whether the image gets written as a pair of interlaced fields or a single frame. If you pull a freeze-frame, edges of moving objects will be smoother on a P frame, since all 480 lines are written all from a single shutter exposure, not a pair of fields separated in time. But that doesn't affect sharpness. In a locked-off shot, the two modes should theoretically be indistinguishable.

It'd help if you added some more info, like:
Are you seeing the shimmer in the viewfinder, live on an external monitor, on playback from the camera, or after loading the footage into an edit suite? Or all of the above? If you're only seeing it in edit, are you viewing footage on a computer monitor, or on a broadcast NTSC monitor?

Is the 'shimmer' an edge effect, or do areas of solid tonality seem to shimmer?

You're not in auto-iris, are you? (Just a D'oh! check...)

If you have external scopes, are you seeing the whole picture's luminance values shimmer on the scope?

Are you viewing composite out? If so, are you talking about dot crawl?

Are you seeing it on all shutter speeds, or did you only test one speed?

You'll definitely see some edge aliasing (stair-stepping) from the HVX in certain situations. I'm aware of it in 480i DVCPro50 mode. Bear in mind, it's an inexpensive camera. That said, I've seen equally jaggy aliasing on a D-Beta camcorder that's only a few years old. You can control it to a degree with your scene settings, but generally you'll see the whole picture soften very slightly when you do. Choose your demon.

Does anyone (Barry?) know whether the pixel-shift on the HVX causes this kind of effect in high-contrast edge areas?
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Old August 11th, 2006, 08:10 PM   #3
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Quote:
Originally Posted by Scott Auerbach
It'd help if you added some more info, like:
Are you seeing the shimmer in the viewfinder, live on an external monitor, on playback from the camera, or after loading the footage into an edit suite? Or all of the above? If you're only seeing it in edit, are you viewing footage on a computer monitor, or on a broadcast NTSC monitor?

Is the 'shimmer' an edge effect, or do areas of solid tonality seem to shimmer?

You're not in auto-iris, are you? (Just a D'oh! check...)

If you have external scopes, are you seeing the whole picture's luminance values shimmer on the scope?

Are you viewing composite out? If so, are you talking about dot crawl?

Are you seeing it on all shutter speeds, or did you only test one speed?
Great questions. Honestly, I saw this effect while using auto-everything, so I need to retest on manual settings.

Quote:
Originally Posted by Scott Auerbach
You'll definitely see some edge aliasing (stair-stepping) from the HVX in certain situations. I'm aware of it in 480i DVCPro50 mode. Bear in mind, it's an inexpensive camera. That said, I've seen equally jaggy aliasing on a D-Beta camcorder that's only a few years old. You can control it to a degree with your scene settings, but generally you'll see the whole picture soften very slightly when you do. Choose your demon.
What things can be done to control it? Lower the detail level? Any help is appreciated.
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Old August 11th, 2006, 08:42 PM   #4
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sample footage?
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Old August 11th, 2006, 10:29 PM   #5
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Quote:
Originally Posted by Bill Edmunds
What things can be done to control it? Lower the detail level? Any help is appreciated.
All 3 detail settings will influence this one way or another, as I recall... my camera's at the office at the moment, so I don't have it to run through the menus. Robert or Barry: you want to jump in on this one??

BTW, ordering Barry Green's book (the order info is a sticky at the top of the HVX main section) is something you should do... he's quite the HVX guru, and Panasonic is giving them away to recent U.S. buyers.

If you were on auto iris, I imagine you'd get some distinct overall shimmer in the kinds of situations you described.
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Old August 12th, 2006, 12:46 AM   #6
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Shimmer

With 480 footage try shooting with Vertical Detail set to THICK, if it is set to THIN you will get the flickers. You can shoot with the setting in THIN but you must lower the detail level to about -4.
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