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What could cause this kind of weird problem?

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Matthew Abourezk
What could cause this kind of weird problem?
on Mar 25, 2012 at 7:39:31 pm

Hi all,

I am editing a clients project and have run into a disturbing problem. Something happened to some of the footage at a certain point in the taping.

Take a look at the enclosed images, one is before the problem occurred, the other after. You will see the problem in the tops of the cabinet doors behind the woman. There are banded colors.

Could this be from the Canon 5D MKII overheating? Except for the few minutes of time that passed, there are absolutely no changes on set or on the camera between the "before" and the "after".

These are the original media clips from the camera. I also notice that despite a tack-sharp focus on the 17" monitor when we shot, all of the footage from this camera is soft.

Any advice is appreciated.





Talkingbox Digital Media Group, Inc.
http://www.talkingboxdmg.com
(203) 249-7718


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Matthew Abourezk
Re: What could cause this kind of weird problem?
on Mar 25, 2012 at 7:56:06 pm

After further investigation, there are two long takes that show this problem. (Unfortunately they are both needed because they are a major section for the edited video.)

The problem is evident from the beginning to the end of each clip. (camera start to stop)
The problem is not evident in the clips before or after the two damaged clips.

The focus is better on the clips that don't show the color problem, but the focus is still not as good as what we saw on the monitor when we shot.

It is just so strange that this shows up only for a couple of takes. We were definitely running the cameras until they hit the 12 minute auto-shut off, but in this case, the camera had been sitting idle for quite a while as we set up for the next scene. I have three cameras running, no weird problems with the other cameras.

Matt

Talkingbox Digital Media Group, Inc.
http://www.talkingboxdmg.com
(203) 249-7718


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Phil Balsdon
Re: What could cause this kind of weird problem?
on Mar 25, 2012 at 8:47:26 pm

Moire, it's very common on HDSLR footage. It happens when fine line detail is at certain "frequencies" so zooming in or out can eliminate it, so can a slight adjustment of focus. It's also more likely to happen when fine lines run at a slight angle like in your example.

It's more predominant in HDSLR cameras due to the line shedding process necessary to get a 1920 x 1080 image from the high mega pixel CMOS sensor.

If you're editing in FCP there's a filter available online called "Moire Buster" but use it sparingly otherwise it'll do strange things to the colour balance of the entire image.

Cinematographer, Steadicam Operator, Final Cut Pro Post Production.
http://philming.com.au
http://www.steadi-onfilms.com.au/


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Matthew Abourezk
Re: What could cause this kind of weird problem?
on Mar 26, 2012 at 11:59:43 am

Hi Phil,

Moire? Ugh. Although I don't doubt you, I have a hard time imagining that moire could be this intrusive on a surface that really doesn't have much in the way of small details. If it is this easy for moire to jump in and destroy a scene, I can't imagine that the 5D (or any DSLR) would have gained the traction it did.

I especially have a hard time imagining that this problem suddenly showed up on two long takes, but is not evident in ANY of the footage shot before or after.

Keeping in mind that this was an 8-hour, three camera shoot (all Canon 5d MKII), and the main camera was locked on a tripod with a 50mm lens all day. Literally locked, no camera moves, no changes in camera settings, no changes in the lighting or set. The only thing the camera operator did on that camera all day was start and stop the recording.

Again, why would the problem appear in only two of the clips from the same camera, not before, and not after, of the exact same shot?

Could this be because of the internal temperature of the camera? Does Moire appear more easily if the sensor is at the top of its temperature range?

Anyway, thanks for the reply.
Matt

Talkingbox Digital Media Group, Inc.
http://www.talkingboxdmg.com
(203) 249-7718


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Phil Balsdon
Re: What could cause this kind of weird problem?
on Mar 26, 2012 at 12:39:42 pm

If they're full frame grabs these shots are a slightly different size. Focus also looks slightly different, is the subject slightly closer to the background?
It can be triggered by just slightly different shot size or focus change.
The colour banding from blue to magenta is typical of moire.

Cinematographer, Steadicam Operator, Final Cut Pro Post Production.
http://philming.com.au
http://www.steadi-onfilms.com.au/


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Matthew Abourezk
Re: What could cause this kind of weird problem?
on Mar 26, 2012 at 1:03:52 pm

Hi Phil. I appreciate you sticking with me on this. I have been researching moire on the Internet and I agree that this is what we are seeing. But this seems more intense and intrusive than most of the examples I just looked at. Also there is no fine pattern.

The screen grabs are from different ounces and are not full screen. I drag-selected the grabs. The good video was a partial grab at 100% from QuickTime player, the bad grab was 100% from fcpx. But the bad footage is evident in those two clips in QuickTime as well.

The focus and relation of the talent to the set was because in one of the clips the talent was not on her mark yet since the grab occurred a few seconds before she started her lines and hit her mark. My bad for not making that part identical. I'll go to my machine and post a full frame grab.

Thanks again,
Matt

Talkingbox Digital Media Group, Inc.
http://www.talkingboxdmg.com
(203) 249-7718


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Phil Balsdon
Re: What could cause this kind of weird problem?
on Mar 26, 2012 at 9:17:02 pm

The fine pattern is the decorative moulding on the cupboard doors. Thats why the moire is occurring in long narrow bands on across the screen on that detail in the screen.

I've had it happen in all kinds of odd situations, often restricted to a patterned area where fine horizontal lines that are predominant on the screen just tilt enough to a slight angle in a small area to cause moire. This type can be the most difficult to detect when recording because you look at the image and don't spot such a minor area in the larger pattern occupying the rest of the screen.

Cinematographer, Steadicam Operator, Final Cut Pro Post Production.
http://philming.com.au
http://www.steadi-onfilms.com.au/


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Peter Burger
Re: What could cause this kind of weird problem?
on Mar 28, 2012 at 8:14:17 am

I'd also say it's a typical moiré issue. Like Phil wrote, slight shifts of focus and/or camera movement can make them occur or disappear.
Especially on those next-to horizontal lines like those on the cupboard.

One way to reduce those problems in post without any third-party-plugins would be to blur the colour-channels (and *just* the colour-channels) a bit. If you have access to After Effects, put an adjustment-layer on top of the footage, add a blur filter (median works best IMHO), set the transfer mode of the adjustment layer to color and tweak the blurring until the artifacts diasppear...

------------------------------------------
"Tragedy is a close-up; comedy, a long shot." - Buster Keaton

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Bob Dix
Re: What could cause this kind of weird problem?
on Mar 26, 2012 at 12:18:11 am

Never had that occur, check with Canon Service, did you manually focus ?

Freelance Imaging & Video
AUSTRALIA


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Brent Dunn
Re: What could cause this kind of weird problem?
on Apr 4, 2012 at 3:29:41 pm

Yeah, that's frustrating. If it was in all of the clips, it would seem a normal issue. The 5D MK III addresses some of these issues and improves on performance.

Brent Dunn
Owner / Director / Editor
DunnRight Films
DunnRight Video.com
Video Marketing Toolbox.net

Sony EX-1,
Canon 5D Mark II
Canon 7D
Mac Pro Tower, Quad Core,
with Final Cut Studio

HP i7 Quad laptop
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