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-   -   Unwanted Strobing effect (https://www.dvinfo.net/forum/jvc-gy-hd-series-camera-systems/86518-unwanted-strobing-effect.html)

Mike Morrell February 14th, 2007 02:37 PM

Unwanted Strobing effect
 
I had someone shoot some footage for me from an HD100 in HDV 30p mode. I captured the footage from his HD100 via firewire using Aspect HD. I have subsequently upgraded to Prospect HD with a PCI-X Aja card.

Most of the footage looks great. But I have about 1/2 a tape's worth of footage that plays back like it is at 15fps. It has a bit of a strobing effect. I'd recapture the footage but I do not own a JVC camera or deck and the person who shot it is out of town shooting with his camera for a few weeks. I have the original tapes. But before I try and rent a camera just to recapture this footage, might the footage have been recorded incorrectly to have this problem?

For example, could the videographer changed the either the frame rate or shutter speed of the camera to where this might have caused the problem with the flickering? I think the entire last part of the last tape has this problem. Could the videographer have made a setting change to the camera without realizing it? If you are shoot at the 30p mode, will the camera allow you to change the shutter speed to something less than 1/30? If I were to get my hands on another JVC camera, is it possible to display on the LCD screen what the settings were when the footage was recorded? If the footage was captured to disk properly and it was a recording setting error, wouldn't the videographer have had to notice the strobing through the viewfinder when he was recording?

Thank you for your help.

Alan Ortiz February 14th, 2007 02:55 PM

I feel your pain
 
I cant help, but I can say that I have the same thing happen to my footage on almost every reel. I shoot with an HD100 non A upgrade and am wondering if this is the source of my headaches? The footage will play fine when I watch it in Final Cut, but sometimes I will dump certain parts to the timeline and Final Cut will turn the footage into a 60p version rather than the 24p that it was shot in. Check the item properties in the viewer to see if you have the same problem, maybe 30p to 60p in your case. I have no clue what Im doing wrong. Anyone else with this problem or something similar?

Jaadgy Akanni February 14th, 2007 03:44 PM

Quote:

Originally Posted by Alan Ortiz
I cant help, but I can say that I have the same thing happen to my footage on almost every reel. I shoot with an HD100 non A upgrade and am wondering if this is the source of my headaches?

Alan, I'm almost sure it is. That strobing problem was what the (A) upgrade was meant to fix, if I'm not mistaken. Look into that.

Alan Ortiz February 15th, 2007 12:41 AM

Crap, well thats not good. I have no idea how to go about getting the A upgrade now. I was just too busy shooting from the moment I bought it last April that I never had the time to send her out. Any ideas?

Mike Morrell February 15th, 2007 06:59 AM

So this problem is with the camera and the footage cannot be fixed?

Tim Dashwood February 15th, 2007 10:40 AM

Quote:

Originally Posted by Mike Morrell
So this problem is with the camera and the footage cannot be fixed?

Mike,

It would be helpful if you could post a short clip of the footage in whatever format it is in right now.

I find that sometimes the use of the wrong term or simple "user error" leads to unjustified assumptions that the equipment is at fault. Let us see the footage for analysis and we can help you identify the issue, and then recommend a solution.

From you description it sounds to me like the camera operator dialed in a slow shutter of 1/15th second. If your motion blurs are extra long, then that may be the issue, and I'm sorry but there would be no solution.

Tim Holtermann February 15th, 2007 01:21 PM

Upgrade to "A" has/had nothing to do with some type of flicker/strobing issue.

I bet the shutter speed changed.

Alan Ortiz February 18th, 2007 10:00 PM

hmmm, well i know in my case that shutter speed is not changing. And it doesnt do this with all of my footage, just some of it. HDV 24p at 1/48 a sec, sometimes it does it, sometimes it doesnt. Like I said, what is bizzare is that it appears fine when I play it in VLC or quicktime, but the second I drop it into FCP the NLE will non-discretely decide to change the frame rate of certain pieces of the footage without warning. Weird. I guess I should have contacted JVC a while back but it tends to be more infrequent than frequent so I just learned to live with it.

Jiri Bakala February 18th, 2007 10:56 PM

Does the footage play properly out of the camera/deck from tape? From your description it sounds more like something happens to it in the NLE, rather than in the camera.

Alan Ortiz February 21st, 2007 01:30 AM

Yeah it only happens in FCP. Now that I think about it though, i just realized that when i convert the footage to AIC 24p using MPEG Streamclip that I dont specify a frame rate. This works 90 percent of the time. Its just the 10 percent that drives me crazy. Think this might be the source of the problem?


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