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Old February 22nd, 2006, 07:21 AM   #1
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DV Image Problem with Checked Clothing

Hi,

We overlooked the problems of wearing checked clothing when filming with DV, so our footage has a kind of visual feedback that results in a sort of contoured pattern in pink glowing lines. I know this is a common problem and something to be avoided, and that there's an actual name for it so maybe you know what I'm talking about,


Is there a way to suppress this in post?

Thanks
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Old February 22nd, 2006, 07:25 AM   #2
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"Moire" is the term you are looking for. And yes, its a common problem. Not just in DV but for film as well. (You usually don't notice it untill you start looking for it.)
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Old February 22nd, 2006, 08:17 AM   #3
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Quote:
Originally Posted by Alex Butterfield
Hi,

We overlooked the problems of wearing checked clothing when filming with DV, so our footage has a kind of visual feedback that results in a sort of contoured pattern in pink glowing lines. I know this is a common problem and something to be avoided, and that there's an actual name for it so maybe you know what I'm talking about,


Is there a way to suppress this in post?

Thanks
There are some still image applications that can remove moire patterns but I don't know about all the different NLE apps. You might have to take the offending sections and export each individual frame through a still image application but that would be a worst case scenario.

-gb-
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Old February 22nd, 2006, 09:36 AM   #4
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Thanks

Moire, thats it, I'm not surprised I couldn't remember, its quite a specific term.

Does anyone know, if it is an actual intrinsic artifact of the video, i mean actually there and will be visible on the negative (if there were one)

or is it just something that appears on screens?

its a fine line but if it is it might be possible to apply very simple effects that might make a huge difference.

otherwise i might have to try and darken those areas quite a lot, we were originally going for quite a silhouetted image anyway so it will be okay for the shot, just a hassle to do. some basi rotoscoping i guess.
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Old February 22nd, 2006, 10:58 AM   #5
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Also, look for the keyphrase "anti-aliasing" or AA. If your editor offers anti-aliasing in a filter, you might be able to clear it up some.
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Old February 22nd, 2006, 07:36 PM   #6
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If you Google "Moire" as I did the other day in regards to a camera with this problem, It will give you a number of explanations as to what it is and what causes It and also ways of reducing Moire in your NLE. Good Luck.
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Old February 22nd, 2006, 10:17 PM   #7
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for my shoots, (corp anyway) i send out an info sheet to the coordinator and give them a "what to do, what to wear"
THis is when were not shooting in controlled environments.

1a- No stripes or checkered shirts. (inc flannel)
1b- No black on Black
2- No Deep "Fire Engine" Reds. (morone and purple OK, and light pinks)
3- Lots of eye makeup for girls BUT easy on the eyeliner

the list goes on, but it helps with the footage
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Old February 22nd, 2006, 11:01 PM   #8
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There are filters available for VirtualDub, to suppress moire artifacting. I have no idea how effective they would be for you.
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Old February 23rd, 2006, 04:21 AM   #9
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Thanks again

I appreciate everyone's replies.

I've googled it for a bit, and understand the problem much better than before, and I'll try out the possible solutions.

I was hoping there would be some plugin filter or something, but perhaps not. I'll try the Anti-Aliasing.

I'm not familiar with VirtualDub but I'll look it up, and thanks Peter for your list. I think our level of production often overlooks things like this. Make-up especially as we are all so inexperienced that we concentrate very specifically on our role, and so other roles that are not assigned get overlooked. Make-up us definately something we've overlooked.

But in future, the role we have will come more naturally and we'll be able to think in a broader way.

Alex
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Old February 23rd, 2006, 08:21 PM   #10
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Ive seen this many times in my 25years in the television industry. Just remember that anything that has close lines of light and shade will give you this effect. eg venitian blinds, check or stripe shirts especially black and white. Good luck
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Old February 23rd, 2006, 08:30 PM   #11
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Thanks Phil. That is the other name you may see it referred to, the venitian blind effect.
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Old February 24th, 2006, 11:42 AM   #12
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There is also Interline Jitter, which is caused by the afore mentioned fine patterns in clothing, but it also appears in other places. For instance, in a shot I saw of a roof, a fine curved line emerges and moves when the camera moves. It's not a moire pattern, but a series of lines that become more apparent when the camera moves.

Some other things to watch out for are: air conditioning grilles, brick buildings, roof shingles, etc. These fine grid patterns along with the tiny 1/3 inch chip make for MiniDV fun. Changing focal lengths can sometimes help as this changes the pattern's size. Sometimes you just have to re-frame your shot.
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