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Moire.......i think?

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Martin Stanesby
Moire.......i think?
on Feb 27, 2015 at 8:46:46 pm
Last Edited By Martin Stanesby on Feb 28, 2015 at 8:26:58 pm

Hi,
Can anyone tell me first off how I got jagged lines on a still object straight edge, with no camera movement against a white background? I've managed to upload a still snapshot of it. It's the horizontal edge, not the vertical edge.

And is there a way I can get rid of it in Vegas?

Thanks

Martin



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Ryan McRobb
Re: Moire.......i think?
on Feb 28, 2015 at 10:47:55 am

Did you intend to upload a video for us to see?
If so, I can't see it.

For what it's worth, I used a NewBlue plugin(the name escapes me) once to add a very slight blur using a mask, unto the checked shirt of an interviewee I once shot, which worked really well.

http://www.ryanmcrobb.com

Asus G73jh Notebook
Win7 64Bit
AMD ATI Radeon HD5870
12Gb RAM
Vegas Pro 13


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Martin Stanesby
Re: Moire.......i think?
on Feb 28, 2015 at 11:06:43 am

Hi Ryan,
Thanks for the response. For some reason it won't let me upload my mp4 file. It's only a 4 second clip of a static shot with no movement at all. It's of a clothes rail, so all straight edges.
I used lighting and a white backdrop. It seems this made the image so clear that the dslr just couldn't handle it so the top horizontal bar has gone all jagged....jjust like when you blow a picture up that hasn't got enough pixels. It's horrid.

Unfortunately any kind of blurring doesn't work here as it stands out too much as though the shot is out of focus.
I can't believe this is an issue with no fix or preventative??
I used a Canon 6D. I do believe it is sharper than the 5D sensor which may be the problem, but I knock the sharpness way down to only one notch....mmy be the one notch is too much also.

Does Neat Video plugins for Vegas work for this problem?

Thanks

Martin


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Bob Peterson
Re: Moire.......i think?
on Feb 28, 2015 at 4:33:28 pm

Another possible explanation is chromatic aberration which is caused by the camera lens. However, without an image to see what you are talking about, we can only speculate. If a problem originates within the camera, it becomes much harder to overcome.


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Martin Stanesby
Re: Moire.......i think?
on Mar 1, 2015 at 9:33:27 am

Hi Bob,
Thanks for your response.

I have now managed to upload a still of the problem.

What's baffled me is that I used two Canon 6D's with different lenses, using different F stops from 1.4 up to 11....and they all have some of this problem. Incidentally, the close up images don't have it but this wider shots have it worse.

Is it cause by the white background to bright, or not enough light? Too much light bring out the sharp detail?

How can a void this because this isn't good enough.

Thanks
Martin


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Warren Eig
Re: Moire.......i think?
on Mar 1, 2015 at 5:56:12 pm

If you take a still image in RAW do you get the same stair stepping? If not then it is H.264 compression in the video. I see the highlights at the top and it looks like compression artifact.

That's just my best guess.

Warren Eig
O 310-470-0905


email: warren@babyboompictures.com
website: http://www.BabyBoomPictures.com


REEL: http://www.babyboompictures.com/BabyBoomPictures/Reels.html


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Martin Stanesby
Re: Moire.......i think?
on Mar 1, 2015 at 8:42:03 pm

Hi Warren,
Thanks for your response.
I'm not sure about that. The original .mov files from the Canon 6D have this distortion. I don't know what you mean about h.264 compression?

Please could you explain for me.

Thanks
martin


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Warren Eig
Re: Moire.......i think?
on Mar 2, 2015 at 4:54:10 pm

Mov is the Quicktime wrapper. H.264 is the compression scheme. H.264 is highly compressed. Try Magic Lantern and Shoot RAW cinemaDNG. It is a 14 bits uncompressed.

Warren Eig
O 310-470-0905


email: warren@babyboompictures.com
website: http://www.BabyBoomPictures.com


REEL: http://www.babyboompictures.com/BabyBoomPictures/Reels.html


For Camera Accessories - Monitors and Batteries
website: http://www.EigRig.com



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Bob Peterson
Re: Moire.......i think?
on Mar 1, 2015 at 9:16:46 pm
Last Edited By Bob Peterson on Mar 1, 2015 at 9:17:52 pm

In my opinion, that is chromatic aberration (also known as color fringing). It is not unusual, and is essentially a defect or limitation of the lens. Changing apertures will not help. Getting closer so that everything is enlarged will help. Yes, I have seen it in my photos where there is a strong backlight which creates a high contrast situation, and fairly well defined edges. There are many discussions of this on the internet. Here is one on Wikipedia;

en.wikipedia.org/wiki/Chromatic_aberration

I think you said you used a couple of lenses. Specifically, which ones? High quality lenses, "L" class or better for Canon, should reduce this problem substantially. Photoshop CS6 has the ability to reduce chromatic aberration within its raw format processor. I am not aware of anything like that for video.


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Martin Stanesby
Re: Moire.......i think?
on Mar 1, 2015 at 9:24:07 pm

Hi Bob,
Yes I've read a few articles on chromatic abberation, none seem to have the jaggies. Photo shop and the likes I see can reduce the colour fringing but when you have jagged distorted lines this can't be rectified with that.
Admittedly my lenses are not top L class Canon, but Tamron.

Thanks
martin


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Bob Peterson
Re: Moire.......i think?
on Mar 1, 2015 at 9:58:13 pm
Last Edited By Bob Peterson on Mar 1, 2015 at 10:02:42 pm

OK, Tamron is the problem, and, yes, I think the jaggies you are seeing are part of the chromatic aberration. When a lens is not perfectly focused, it will produce this sort of distortion. As the article noted, reducing the contrast is one way to reduce the problem. A different background color should also help although some colors will work better than others.

One other thing to think about is the importance of the problem. I have noticed that many glitches that you can see in an image will not be noticed in a video. People will simply not see many of the things that you do because the image is changing quickly and we tend to sit much farther away from the screen.


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Martin Stanesby
Re: Moire.......i think?
on Mar 2, 2015 at 10:32:02 am

Hi Bob,
Thanks for the pointers.

so, if a stop down as far as I can go, focus is sort on then I shouldn't have this problem?
Do you think the brighter the lighting on the white the more it would bring out the contrast on the edges? I would consider reducing the lighting and brighten, or mask out in post.

That's an interesting point you mention about glitches in video. I think if this wasn't a still shot then it wouldn't stand out so much. However, sometimes when the image is moving it can highlight it as there's movement around the jaggies.

Thanks
Martin


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Bill Bruner
Re: Moire.......i think?
on Mar 2, 2015 at 2:21:18 pm
Last Edited By Bill Bruner on Mar 4, 2015 at 7:27:23 am

This problem is called "aliasing". It is separate from, but related to "moire".

Aliasing is the jagged distortion of continuous lines, while moire is an interference pattern created when there are thin lines in your shot.

Nice article on this here: http://www.istockphoto.com/article_view.php?ID=1032

Canon's downscaling algorithms are the culprit. Taking a 20.2MP sensor and "throwing away" 18 million pixels to create a 1080p image requires a lot of processing power, and Canon DIGIC processors and algorithms are notoriously bad at this (one of the reasons I sold my Canon DSLR).

One answer might be a $365 Mosaic anti-aliasing filter.

Another answer might be to trade up to a (recently marked down) $2499 5D Mark III or a $3999 Canon C100 camcorder - cameras where Canon paid more attention to solving this issue.

There is really nothing you can do about it in post.

Good luck!

Bill
Hybrid Camera Revolution


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Michael Gissing
Re: Moire.......i think?
on Mar 3, 2015 at 11:34:12 pm

Looks like line skipping causing aliasing. Can't see any chromatic aberration.

The in camera filters that help this are basically blurring the picture. The sharper the lens the more obvious this can be. My 16-35 on a 5Dmk2 is terrible for this. You could try a slight blur which will soften the image.

H264 can also make things worse but this looks like line skipping to me. My solution is to now shoot 4k video on a Blackmagic camera and use the 5d to shoot stills RAW.


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