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HPX-500 + Strobelight = Problems!

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Nicolas Borrell
HPX-500 + Strobelight = Problems!
on Aug 10, 2008 at 12:52:05 pm

Hey guys,

Didn't think things could get worse with this camera, but now I find myself with a new problem;

Using the Panasonic HPX-500, I was shooting a crime scene and recording the strobe light on top of a police car.
When editing, I noticed that approx. every 1-2 seconds, the image will distort and even roll - as jumping in and out of sync. Why does this happen? At first I thought it looked like rolling shutter - on a CCD chip camera??? Is the blue strobe light too much for the camera chip to handle?

Was using the following settings during the shot:
576i 25i
DV
50 hz
Custom Scene file, with all settings set to 0, except masterblack set at -3, and set to videocam
No shutter
3db gain

What say you experts on the Internet. What say you Jan Crittenden Livingston???

Link til footage1 (Raw video): http://www.vimeo.com/1501733
Link til footage2 (Frames in question): http://www.vimeo.com/1501829


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Rennie Klymyk
Re: HPX-500 + Strobelight = Problems!
on Aug 10, 2008 at 5:51:46 pm

[Nicolas Borrell] " Is the blue strobe light too much for the camera chip to handle? "

It would be interesting to take a light meter reading of the blue strobe as it's beam shoots directly at the sensor at that distance and take a look at the ev of the entire scene. Even film would choke on this scene at that moment. Lens aberrations occur under these circumstances. An apo prime would be best suited for this type scene. We're not supposed to aim our ccd's directly at the sun but I wonder where the cut off or break point is. The old tube cameras had troubles with street lights in night scenes so I'm not surprised if this chokes a ccd. If the blue strobe aimed directly at the lens was a constant source it would need to be shot at F22 with maximum neutral density applied.

DV compression can enter the equation too. How does it look playing straight off the camera to a good monitor? It has to produce an illegal ire value for broadcast standards and that can create havoc with sync. Where the sync issue occurs (ccd-DV compression-NLE) would be interesting to find out.

There are a lot of variables here, hopefully some techie gurus will chime in. Thanks for posting.


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Jan Crittenden Livingston
Re: HPX-500 + Strobelight = Problems!
on Aug 10, 2008 at 8:20:51 pm

Rennie may be on to something, I too questioned the framing of the one strobe so close. But it also could be that there is some RF interference coming from the Police Vehicles and their associated radios? Couldn't say, have never seen anything like this from a CCD. My suggestion is to take it to a Panasonic service center and have them evaluate it with the footage in question. See what they have to say. You may get an answer close to Rennie's.

Best,

Jan

Jan Crittenden Livingston
Product Manager, HPX500, HVX200, DVX100
Panasonic Broadcast & TV Systems



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Nicolas Borrell
Re: HPX-500 + Strobelight = Problems!
on Aug 10, 2008 at 9:29:14 pm

Thanks for the reply guys,


Rennie, those are interesting thoughts. But if the image is overexposed I would think that the in-camera whitecutter would bump down the whole signal, and not distort it as it is now.
I upgraded to the HPX500 from a Sony FX1, and I've done hundreds of shots like this on the FX1 without ever seening anything like this.
I would be shocked if a better and more expensive camera like the HPX500 would not be able to handle such shots. At the TV-station I work, I daily see footage from ambulance chasers, shot with really cheap cameras - And I've never seen this before.

In Avid - thru Mojo - I get the same image.

Jan - I guess that could be the problem. But again I would find it very shocking if the HPX500 can't handle something that the FX1 can do problem free.

I'm goning to do some more test:
Shoot same situation in different formats, with different lenses and exposures.
Check sync signal compared to waveform numbers.

I'll report back here.



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Jan Crittenden Livingston
Re: HPX-500 + Strobelight = Problems!
on Aug 11, 2008 at 1:15:28 pm

Hi,

I think the problem is that the framing of the two light sources and the closeness of one might be the problem. I have never seen anything like this but I would bet that if the 500 did this so would any CCD in the exact scenario. I have seen the HPX do strobe lights before, just not in this composition.

The white clipper would not affect the entire image, only the area that is over.

Best,

Jan

Jan Crittenden Livingston
Product Manager, HPX500, HVX200, DVX100
Panasonic Broadcast & TV Systems



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Rennie Klymyk
Re: HPX-500 + Strobelight = Problems!
on Sep 2, 2008 at 11:15:14 pm

Hey! I just saw this camera on ebay and thought I'd toss it out here.

Check this guys description out:

http://cgi.ebay.com/JVC-GY-DV500U-MiniDV-3CCD_W0QQitemZ250290133185QQihZ015...

Seems he was recording a live event with some laser lights in the show and his ccd got fried. I know there are 3 levels of lasers and only certain ones are recommended for around humans so you'd think any lasers being used for a light show at an event would be of the recommended type and not that powerful, (never read anything about spectators at an event being blinded lately). Anyway if this guy's presumptions are correct, a low level laser safe enough for humans' eyes has fried a few pixels on his ccd's.

The old tube cameras used to "come back" if there was any burn in from a strong light source by aiming it at a white subject for a while although I'm sure they could be fried easily enough under these circumstances too. It seems ccd's can burn out their pixels completely.

I'm not up on how the whitecutter works but this was my thinking, just a spear of light comes in from left center field and it's not spread out enough to effect the overall "average" exposure and shut any thing down. In the way this guy's laser just fell on a few pixels out of the whole scene being recorded on the ccd's, your strobe although not as concentrated or powerful was still enough to frazzle the ccd's a bit but thankfully only temporarily. Whether this is actually frying the ccd's or more likely just overloading the DSP circuits that represent the effected pixels is a mystery to me. At any rate there does seem to be a threshold on how sharp and how bright a beam of light can be before it creates havoc with a ccd and the underlying DSP that translates and carries the image afterward.

"thou can not stir a flower without crumbling a star" ......Henry Wadsworth Longfellow


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