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Keying out Black Artifacts in White areas

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Brian SimonsKeying out Black Artifacts in White areas
by on Jan 27, 2011 at 4:22:10 pm

I recently exported a finished wedding movie as an uncompressed AVI from Premiere Pro CS5. After that export, which was luckily to a different drive, the drive with the original project died and all I have is the finished master file.

In the rendering it created these little black artifacts dancing around overexposed areas of the image. Since I can't reopen the project and try rendering out a new clip, I am left with this file with this problem. The artifacts are pure black and they are always located in areas that are pure white. I've been trying to figure out a way to key out just the black, but any general luma key takes out blacks I want to keep as well.

I'm sure this can be dealt with and I just thought rather that farting around all day I'd see if someone who is much more experienced with keying had a good method I could employ to filter out these artifacts.

I just uploaded a still image that shows what's going on. The link is: 1552_weddingartifacts.jpg.zip

Thanks in advance to anyone who can help.


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Dave LaRondeRe: Keying out Black Artifacts in White areas
by on Jan 27, 2011 at 5:58:18 pm

Was the video always this overexposed?

You'll need three layers to fix this, in this order from top to bottom:
  • The video, with animated masks around the areas with noise
  • A pure white layer, with the same animated masks from the video: you can copy and paste them
  • The video, with NO masks

Key out the black on the top layer.

Depending on the severity of the noise, you could face a long, long repair job.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Joey ForemanRe: Keying out Black Artifacts in White areas
by on Jan 27, 2011 at 6:25:33 pm

And with high number of Roto Masks you'll need, and the complexity of their animated shapes, you might find it faster to just paint out the specks, frame by frame.

Joey Foreman
Editor/Compositor/VFX Artist


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Brian SimonsRe: Keying out Black Artifacts in White areas
by on Jan 27, 2011 at 7:29:56 pm

Eesh. I do know how to do either mentioned method..I guess I was hoping that there were a way to isolate the problem more generally. It was probably just optimistic thinking because I didn't want to come to the conclusion that I'd be making tons of moving masks or painting frames.

Thanks for the advice. I'll re-assess just how much material there is deal with and go from there. I have all of the raw material that was shot but have lost the project file. It pains me to think of re-editing the whole thing but that might be just as fast or faster than dealing with the black artifacts. I've never had anything like this happen before. I've had random things occur during rendering, but not this. None of this showed on the NLE timeline, it all was a result of final export.


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Greg RobbinsRe: Keying out Black Artifacts in White areas
by on Jan 28, 2011 at 2:02:29 am

You could try to do a similar thing Dave said, but this way will save you from all that work.

Duplicate the layer, and make the new layer black and white. Then using either levels or threshold, adjust it so that only your brightest whites stay white and everything else is black. Then use the minimax effect or a matte choker to expand the white area just enough to cover those small black artifacts.

Then make the new black and white layer a matte of the original footage.

Then create a new white solid and place it on the below the other 2 layers.

If my thinking is correct, the top layer should be a mask eliminating all white, and with the minimax it should eliminate your problematic black spots. And since you have the white solid below it, that should replace the white and the problematic black areas you keyed out.

Hope this works, let me know.


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Greg RobbinsRe: Keying out Black Artifacts in White areas
by on Jan 28, 2011 at 2:10:16 am

Ok I just tried it with your jpeg you posted and it worked for me.

Just one thing, when you put the minimax effect on, switch the operation from "maximum" to "maximum to minimum"


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Walter SoykaRe: Keying out Black Artifacts in White areas
by on Jan 28, 2011 at 2:43:45 am

Hi Greg,

I think this will work, too, but won't using Minimax to create a mask which reveals a white layer blow out some good highlight detail along with the black spots, especially on the dress? That's why I was suggesting a similar technique as a mask limiting a Change Color effect on blacks.

Certainly, though, both of these techniques beat painting out all those frames...

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Brian SimonsRe: Keying out Black Artifacts in White areas
by on Jan 28, 2011 at 3:17:04 am

Thanks for all the ideas. I'm going to try the last few and see if I can get something desirable.

I'll let you know how it works out and which method I used. Thanks again.


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Joey ForemanRe: Keying out Black Artifacts in White areas
by on Jan 28, 2011 at 3:54:32 am

I never cease to be amazed by range and depth of the toolset in AE, nor by the ingenuity of its users.
I had been thinking along the lines of Procedural Matte Creation, and had fooled around with a combination of techniques on the shot, but came up short.

Thanks, Walter and Greg, for the insightful tips.

Brian, hope my initial assessment didn't dampen your spirit for any significant amount of time.
Good luck fixing it up.

Joey Foreman
Editor/Compositor/VFX Artist


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Walter SoykaRe: Keying out Black Artifacts in White areas
by on Jan 27, 2011 at 9:59:11 pm

It's not a perfect solution, but I got pretty good results on your test still by precomping the footage, then using Threshold and Median to create a luma matte for an adjustment layer over the original footage. The adjustment layer uses Change Color, with black in the picker and a Lightness Transform of 100.

Threshold, Median, and Change Color's tolerance are all seasoned to taste. I used 128, 2, and 11 (respectively) on this still.



Essentially, this smears out the interior of the highlight areas (while keeping the edges relatively sharp), then only looks in the highlight areas for black pixels to change to white.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Angie TaylorRe: Keying out Black Artifacts in White areas
by on Jan 28, 2011 at 8:28:06 am

Hi there,

Great ideas from everyone, it just goes to remind us that there's definitely more than one way to skin a cat in AE! ;-)

You could use Keylight for this, it has lots of tools built in to help with this kind of issue and is very powerful. The Scree De-spot Black settings can be used to remove the black 'flecks' and you can determine the area you want to restrict this by creating Masks and using the Inside Mask and Outside Mask settings. I have a free tutorial here, it's quite old but the steps still work;

http://www.angietaylor.co.uk/free-tutorials/

I hope this helps.

cheers,

Angie

Angie Taylor animation & illustration for television, film, web and devices

http://www.angietaylor.co.uk
Twitter: theangietaylor
Linkedin: theangietaylor
http://www.facebook.com/pages/Angie-Taylor/118378194869002



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Walter SoykaRe: Keying out Black Artifacts in White areas
by on Jan 28, 2011 at 9:34:47 am

[Angie Taylor] "Great ideas from everyone, it just goes to remind us that there's definitely more than one way to skin a cat in AE! ;-)"

Challenge accepted!

Another approach is isolate the shadows and smooth them selectively.

Duplicate the footage, Invert it, and set a high-ish Threshold value (I used 230 on this still). Use that as a luma matte on an adjustment layer (or another duplicate of the footage) with either Median (at around 2) or Minimax (with Greg's suggested settings), all over the original footage.

Any other takers?

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Angie TaylorRe: Keying out Black Artifacts in White areas
by on Jan 28, 2011 at 11:23:49 am

LOL! It wasn't really intended as a challenge but thanks for sharing! ;-)

cheers,

Angie

Angie Taylor animation & illustration for television, film, web and devices

http://www.angietaylor.co.uk
Twitter: theangietaylor
Linkedin: theangietaylor
http://www.facebook.com/pages/Angie-Taylor/118378194869002



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