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Old December 26th, 2008, 09:01 PM   #1
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DSLR Flash Interference

I shot a weeding 2 weeks ago and during the editing, saw something which never happened before. for about 1 second the entire footage seems to be affected by some foreign frequency. I have uploaded the footage on vimeo (1.86Mb file size). If you look carefully, before the thing happen, the Nikon DSLR fash near me was throwing out the infrared focus assist light. I suspect that was the culprit. But the photographer was my partner and we have shot more than 10 weddings since I got my EX1 in Feb, and this is the 1st time it happened. I can't imagine if this happen during the bride or groom says ' I do'

Is this another CMOS related issue? Anyone got same experience and manage to find solution? Shooting mode was SQ 1080 50I mode, shutter off and flicker off. I don't think this got anything to do with the fluroscence light frequency too.

Untitled on Vimeo
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Old December 26th, 2008, 09:23 PM   #2
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The Video sure looks like a combination of interference from RF and a light interference issue as well. Unless you can duplicate it will be difficult to say exactly what happened. How close to the camera was the flash unit? Definitely worth a test. Also sometimes RF interference can come be induced in equipment if the covers are loose or connectors are not covered as the signal now has a way to get inside the camera. By any chance have you lost some piece which used to cover a part of the camera. Also the photographers flash unit might now be a bigger source of RF than it used to be. Flashes have to generate a high voltage so they sometimes emit more signals than just the light.
Intermittent issues are difficult to nail down with any system so you should try and force the issue to happen. Was the audio track effected during the interference. You can also ask Sony if they have any ideas but there are a lot of potential RF interference generators these days with cell phones, walkie talkies, radio mics wireless networks, flourescent fixtures ballasts so cameras have to be shielded against these sources and sometimes the shielding fails.
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Old December 26th, 2008, 09:31 PM   #3
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The audio was fine. The flash was about 1.5m away from me. The audio and I-link mini cover on my EX1 were broken just 1 week after I owned the EX1 but I have since use blue-tag to cover it from dust.

I have another shoot with the same photographer next Sat, I will try and re-create the sceneario.
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Old December 26th, 2008, 09:36 PM   #4
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John, as you may well know, many of the newer flash units can trigger a slave via an RF link. My Sekonics light meter has an optional RF module to fire off slave flash units for light measurement.

If the photographer has such a unit, that may be the interference source. In trying to recreate the scenario, try having him shoot with, and without the flash unit to see if those interference lines show up.

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Old December 26th, 2008, 10:47 PM   #5
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We saw that same anomaly here on the list a couple months ago but I can't remember who posted the footage. It was shot near a pool and had the same rolling "density bars" or whatever you want to call those lines. You might need to do a search but I'm not sure if anything was ever resolved but I don't believe there was ANY flash photography going on in the previous incident.
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Old December 27th, 2008, 01:43 AM   #6
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I notice that the white balance changes when the strobing starts, taking on a distinct blue tint and the amount of light on the grooms face seems to increase. Did someone turn on a fluorescent light? Have you switched off the flicker reduce? It could be that the focus light from the DSLR was triggering the flicker reduction shutter.
Alister Chapman, Film-Maker/Stormchaser http://www.xdcam-user.com/alisters-blog/ My XDCAM site and blog. http://www.hurricane-rig.com
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