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Old June 21st, 2009, 01:30 PM   #1
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slow motion flickering, 50/60 fps for PAL?

Hello, im noticing that when im doing some slow motion shots lately that im getting a strobing/flickering effect on the entire image and im wondering if it has anything to do with my setting the in camera s&q function to 60fps instead of 50 seeing that i am shooting in PAL.

The first time i noticed it was when i was shooting under fluorescent lighting which i kind of expected to happen, however yesterday i was filming an outdoor scene with no artificial lighting and i noticed this same problem. I didnt get chance to play around with different settings but i plan to, however i was hoping in the meantime maybe someone could chime in with any similar experiences/solutions?

Note, i have flicker reduce on and set to 50 hertz.

Thanks guys
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Old June 21st, 2009, 01:51 PM   #2
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Were you panning/tilting on a moving subject by any chance?
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Old June 21st, 2009, 05:26 PM   #3
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Shooting 60fps under 50Hz lighting is kind of inviting problems like this. I've found even shooting 24fps where there's 50Hz fluro lights with iron ballasts to produce nasty rolling bands with another camera.
Either shoot 50p or use lighting with high frequency ballasts.
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Old June 21st, 2009, 05:45 PM   #4
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Shooting 60fps under 50Hz lighting is kind of inviting problems like this. I've found even shooting 24fps where there's 50Hz fluro lights with iron ballasts to produce nasty rolling bands with another camera.
Either shoot 50p or use lighting with high frequency ballasts.
He's talking about seeing it in natural daylight though, so you can rule out the 50Hz thing.
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Old June 21st, 2009, 05:55 PM   #5
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Is this happening on the LCD viewfinder as you shoot, on your computer on playback, or on a HD television on playback? You will often see stuttering on the viewfinder or computer, but it's perfect on a HD tv due to mismatched refresh rates or slow computer, etc.

More information needed.
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Old June 21st, 2009, 09:13 PM   #6
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Ok i have an assumption of what the problem could be but it really is only that, not enough technical knowledge to back it up scientifically. My GUESS is that it may be the image stabilization built into the camera causing these strobes and il elaborate on why...

I've analyzed my footage again and viewed it on the lcd of the camera, a 24inch 1080p computer monitor and my 40inch lcd tv hooked up to my blackmagic card (outputted through HDMI on a YUV signal) and the strobing is there on all three screens, however on some shots the strobing isn't apparent until a little way into the shots or sometimes its in the shot to start with and then disappears as over objects enter the frame. (shots were hand held), im thinking that the strobing is more pronounced when there is a lot of white in the scene as i first noticed this problem when i was filming a necklace swinging in slow motion in an all white studio. At first i thought it may have something to do with over exposure as i kept noticing the strobing on shots where i allowed my whites to bloom (sky etc) but i noticed the strobing was still apparent on shots where my luminosity was within the legal limits.

Im real confused right now, especially at the fact that this is happening under natural light and intermittently. I plan to test shoot some footage outside tomorrow to see if i can isolate the problem down to a hertz setting (im sure i learnt somewhere that natural light had different effects on camera technology around the world), see if its the image stabilizer or see if im getting the problem when the camera is attached to a tripod/stationary.

If anyone has any new thoughts id love to hear them, thanks.
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Old June 22nd, 2009, 02:34 AM   #7
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I saw problems without the IS, it's a rolling shutter thing I'm sure, though I was shot down in flames for saying say so! See http://www.dvinfo.net/conf/sony-xdca...ing-birds.html

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Old June 22nd, 2009, 06:07 AM   #8
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He's talking about seeing it in natural daylight though, so you can rule out the 50Hz thing.
Steve
Oh yeah, missed that bit :)

However:

Quote:
Note, i have flicker reduce on and set to 50 hertz.
Sony recommend having it Off unless you know you need it On.
It would seem that sometimes it can increase flicker and I can imagine panning across some scenes could cause the flicker reduction logic to flip out. I'd certainly try turning it Off. I keep mine set to Off.
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Old June 22nd, 2009, 06:53 AM   #9
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Quote:
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Sony recommend having it Off unless you know you need it On.
It would seem that sometimes it can increase flicker and I can imagine panning across some scenes could cause the flicker reduction logic to flip out. I'd certainly try turning it Off. I keep mine set to Off.
Yes - even the firmware update changed the default setting from AUTO to OFF.
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Old June 23rd, 2009, 01:50 AM   #10
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Same problem here.

Intermittent flickering during daylight hours. I looking around to see if the was ballast lighting..... but..... there wasn't.

I sure hope there is going to some funky software that is going to correct this. Nice work Sony!

I wonder what 'issue' is going to surface next.
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Old June 23rd, 2009, 02:28 AM   #11
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I would have to say that if there are a few "issues" it shouldn't be too much of a surprise, after all there must be some reason why these wondercams suddenly appeared that on paper are as good as or better than those costing 10 times as much.
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Old June 23rd, 2009, 03:22 PM   #12
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We've seen this flicker issue crop up several times on the forum and I have experienced it myself in the past. It has in all cases I've seen been caused by having flicker reduce set to "on". As has been suggested a simple pan or camera move can be enough to trigger it's operation. It seems to be particularly bad if you are already using the shutter, such as a 180 degree or 1/50th shutter when shooting 25P.

So my advice is to always turn flicker reduce OFF.
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