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EX1 and wobbly footage

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Daniel Stone
EX1 and wobbly footage
on Sep 12, 2008 at 3:51:40 am

We rented some Sony EX1 cams for a drag racing documentary and were shocked when watching dailies. Everything filmed in 60 fps (slow motion) where the camera wasn't completely locked down looks wobbly, almost like Jello. All vertical lines sway back and forth as if swaying in the wind with any latteral movement of either the camera or the action (and we're talking small movements here). The footage is completely unusable which is a shame because it would be beautiful if not for the Jello effect.

I did some research (which I should have done BEFORE renting these cams) and discovered that this is called "rolling shutter artifacting". Does anyone else know of a way to avoid this issue? We have 2 more weeks of filming and we're considering ixnaying the EX1s and switching to HVXs.


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Craig Seeman
Re: EX1 and wobbly footage
on Sep 12, 2008 at 4:08:15 am

Can you post a link to the shot so we can view? A good H.264 MOV file should hold up well and be small enough to download.



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Don Greening
Re: EX1 and wobbly footage
on Sep 12, 2008 at 5:40:47 am

Daniel,

Have a look at the .mov file at the link below. You have to have the EX codec on your computer in order to view the video clip. If what you observed from your shoot is similar then there's a problem with the EX cameras you rented and is not the norm. They might be early versions of the EX1 and some of those suffered from a failure of the optical image stabilization systems. My first EX had this problem once but it wasn't anything like the sample from the provided link below. I can assure you that healthy EX1 cameras do not have the problem you've described. I shoot overcranked footage all the time and have never seen this issue on my present EX. Here's the link:

http://www.solpictures.com/xdcam/

- Don


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Daniel Stone
Re: EX1 and wobbly footage
on Sep 12, 2008 at 3:33:32 pm

Hi Don -

Thanks for sending that link. Kinda but not really. It only happens when the camera or the subject moves. It's like the bottom part of the screen lags behind the top part. When the camera moves, the image follows like the worm in that old Atari game.

I've attached a file which is actually a very mild example of the problem (it's the only on I had on my lappy). This sample is 720p30. It's even worse in 1080p24, and all 4 cameras are doing the same thing. Here's the link (will stay active for 7 days): https://www.yousendit.com/download/bVlBek9uTWNoMldGa1E9PQ

I've done some more research and have found that this is a common concern with the EX1 because of the way the CMOS captures the image (not sure what that means). Though I hate to write off the EX1s, it's enough of an issue that our exec producer is funding an upgrade to Panasonic HDX500s (couldn't find enough HVXs for rent for the amount of time we need them). Would still love to find a solution if anyone knows of one so I can be the hero.

Thanks again, guys, for your help and suggestions.



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Don Greening
Re: EX1 and wobbly footage
on Sep 13, 2008 at 12:41:04 am

Hi Daniel,

I've been waiting for others to have a look at your yellow Mustang clip and offer an opinion but no one else has stepped up yet. Personally I can't see a whole lot wrong with the clip other than the camera shake. Unless I'm really missing something. Could it be something as simple as shutter speed? Were all 4 cameras set to the same shutter? Minimum shutter should be 1/48th for 24p and 1/60th for 30p and 60i. Unless I'm missing something.....

I've done 180 degree pans in about 2 seconds with my EX shooting in HQ 1080p 30 @ 1/60th and have found the results acceptable, even handheld. I can point you to the sample if you want.

I'm not being very much help, am I?

- Don


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Denis O'Keefe
Re: EX1 and wobbly footage
on Sep 13, 2008 at 6:48:35 pm

I just looked at the yellow mustang too, I too must be missing something. Was the camera on a tripod or mount of some kind? It looks like the view through my nikon d-70 with the vibration reduction lens not set up right.
The video looks right, its appears to be the shot that is dancing around.



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Daniel Stone
Re: EX1 and wobbly footage
on Sep 14, 2008 at 6:09:43 pm

Hey guys,

The shot is, indeed, handheld and the camera operator is causing it to move back and forth - though that's not the issue. The issue is what the image does when the camera does move back and forth. Watch the side of the car and how it flexes and skews as the camera changes direction. The side of the car appears to tilt toward and away from the camera.

We've talked to a lot of people about it in the past week from post guys to camera "experts", and we've done a lot of experimenting - and here's what we've found (I'm sharing this as an FYI):

The EX1 has a CMOS sensor which scans the image from top to bottom, where a CCD sensor scans the image all at one time. This is what causes the EX1 to skew what it sees under certain conditions. Here's an excellent explanation and demonstration: http://dvxuser.com/jason/CMOS-CCD/

We have learned that CMOS cameras are not recommended for high-action footage (should have done research before we started), footage containing strobing, fast-changing lighting situations or anything that needs to be tracked in post. We talked to another production team from Nat Geo who had the same wobbling issues and, coincidentally, digital media cams (including P2) are no longer allowed for Nat Geo-funded projects (though I'm pretty sure this is just mandated by a technology-phobe bigwig). We're going to be tracking titles into some of this slo-mo footage for network promos and our post guys said the skewing makes it a no go (it's certainly possible - it just wouldn't look very tight).

We did some testing and here's what we found makes the skewing/wobbling most noticeable (it's the same for all 5 cameras we tested): filming in 1080p/24, slow motion (though it also does this in regular speed), long zoom, open iris and slow to medium-paced change in direction (such as the back-and-forth motion of a long-lensed hand-held shot). Do this: zoom into a vertical line from across the room, open the iris, put the cam in 60fps (slo mo) mode and move laterally back and forth slowly so the line takes about 1-2 seconds to cross the screen. Then watch it back and see how the bottom of the line catches up to the top of the line as you change direction.

Conclusion: we have to see the camera for what it is- a prosumer documentary solution with some additional cool features. We were trying to squeeze in some promo-worthy "beauty" shots on the fly which should have been done with a different cam. I am certainly NOT saying that the EX1 doesn't make beautiful images - it's just that we shouldn't have expected Sony F23 results from the EX1. For normal documentary filmmaking which includes talking heads and standard cinematic b-roll this camera is excellent. And, to be honest, the average viewer probably wouldn't care (or even notice) -- and to those wowed by 1080p the image size may make up for any other imperfections. Every camera certainly has its downfall but this is definitely a biggie for us.

Thanks again for taking the time to check out my footage and give your thoughts.



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Randy Lee
Re: EX1 and wobbly footage
on Sep 15, 2008 at 3:24:44 pm

While I haven't had the opportunity to shoot with the EX-1 yet, I've recommended quite a few professionals, including the company that I work with, to stay away from it for exactly this reason. It seems like most viewers don't notice or care very much about the wobbly footage, but it is definitely an issue if you know what you're watching for. My question is: is this just an issue with the EX-1? That is about the only camera that I've heard about having rolling shutter issues. I haven't heard about RED, also a CMOS sensor, having problems, or the EX-3, or any other cameras. If it is only the EX-1, then come on Sony, step it up. Don't use us as guinea pigs and sell us wobbly crap as prosumer equipment. If it isn't just the EX-1, then who's dropping the ball and not telling us about the other cameras having issues?



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Denis O'Keefe
Re: EX1 and wobbly footage
on Sep 15, 2008 at 6:02:06 pm

Daniel, sounds like a real mystery - when I looked at the footage after your second note I could see the wobble you're talking about; subtle, but definitely there. It seems strange, neither the car or the camera seem to be moving too quickly.
You might be doing us all a favor by sending the bpav files to Sony for a diagnosis.
If you hear anything or do get to the bottom of the issue please let us know what's up.



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Daniel Stone
Re: EX1 and wobbly footage
on Sep 15, 2008 at 8:06:35 pm

Our executive producer talked to someone at Sony who said they're aware of the wobbling issue and that this is just a characteristic of the CMOS chip set. He said that CMOS chips are a lot less expensive than CCD chips and noted that CCD chips would have increased the price of the EX1 quite a bit - so understandably they decided to keep the EX1's price point down by using CMOS sensors. Where now they have a few guys like me complaining about wobbling, with CCD ships they'd have a lot of people complaining about price.

There are also some technical reasons why they went with this chip (some having to do with the compression which I'm not smart enough to understand) - one of which is something about the amount of processing power and heat produced by CCD chips (which is a reason the RED camera uses CMOS chips).

Interestingly enough we shot a music video with the RED camera a couple of weeks ago and the only issue we had in relation to the CMOS sensor was half-exposed frames from a strobe light which we fixed by killing the strobe light. I know they did something internally to minimize rolling shutter artifacting, though I don't know what. Don't get me started on the RED's shortcomings, though. At least the EX1 turns on without having to do a happy dance. Ugh.



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Don Greening
Re: EX1 and wobbly footage
on Sep 15, 2008 at 9:45:39 pm

[Randy Lee] "I haven't heard about RED, also a CMOS sensor, having problems, or the EX-3, or any other cameras."

Well then you haven't been to the reduser.net forum, because there's all kinds of posts (and extensive test results) concerning the RED's CMOS "picture skew" issues. Look for a test where someone set up a bunch of white vertical lines on a black background and panned the RED ONE rapidly back and forth. There's video of that test at RED User.

The EX3 is exactly the same internally as the EX1 so the rolling shutter and picture skew issues are common to both. To minimize picture skew with the EX series cameras you need as much temporal resolution per second as possible. This means shooting HQ 720p 60. That's why Sony used this setting when the company put bunch of EX1's in several aerobatic airplanes and posted the results on their website. Footage looks awsome.

- Don



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Ronnie Martin
Re: EX1 and wobbly footage
on Sep 21, 2008 at 8:59:45 pm

How does the HQ 720p 60 footage compare to 1080i 60 down converted to SD when shooting fast moving objects? I shoot dirt racing at night where the light changes every 50-60 feet and the cars are moving at over 100mph and have been using 1440X1080i shutter at 60. The results have been pretty good except for some artifacts on horizontal lines when down converted then burned to SD DVD. The main issue that I have had is nailing focus. My perch is usually way up on a press box and I am shooting down following the cars around the track. When the light is low the depth of field is shallow. Most of the time focus is set to infinity but infinity is not against the infinity stop on the Fugi lens on the EX. It keeps changing. Is this a camera issue or pilot error on my part? The footage when viewed on my Sony HD monitor is super. It is when the down convert to SD on the timeline the artifacts occur. The Editing platform is Edius 4.61.

Thanks
Ronnie Martin
http://www.dirtracingvideo.com


Ronnie Martin
Kato Video Productions


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