Chroma Key: Jagged Edges?! (FCP & Motin 3)

[lilnyc]

I chroma keyed a video using Motion's Primatte RT filter. The green was removed, but there are (white?) jagged edges around the subject. I have attached two screen grabs so that you can help me:

I have these apps if you feel I should try another way:
Final Cut Studio (w/Motion 3)
After Effects CS3
Shake

I was advised to use Shake by one person. Please let me know what you recommend.

Thanks in advance!
Contact me faster at NYImport@gmail.com

 

[killmoms]

Shake also has a Primatte filter (although its more advanced one is keylight's). You should be able to get a good result with Primatte in Motion, perhaps tweaking the falloff/softness of the mask would help some.

 

[lilnyc]

Shake also has a Primatte filter (although its more advanced one is keylight's). You should be able to get a good result with Primatte in Motion, perhaps tweaking the falloff/softness of the mask would help some.

Hi Killmoms,

I used the Matte Magic filter in Motion 3 (thanks to Ripple Training) and adjusted the Shrink and Feather settings. That resolved the white around the jagged edges. It looks better, but I worry that the edges are not perfectly smooth yet. So I'll try your suggestion as well as a tutorial on Lynda.com for Shake.

 

[LethalWolfe]

What is the source footage? If it's DV then you are going to run into the limitations of the codec pretty fast. Also, if you work in an uncompressed environment (even if you are working w/DV footage) you'll get a little more headroom w/regards to tweaking the footage.


Lethal

 

[lilnyc]

What is the source footage? If it's DV then you are going to run into the limitations of the codec pretty fast. Also, if you work in an uncompressed environment (even if you are working w/DV footage) you'll get a little more headroom w/regards to tweaking the footage.


Lethal

I believe it's HDV. The source file ratio is 1440x1080, Animation codec. They are on a hard drive, so I don't know much other than what info I can pull from the metadata.

 

[ppc_michael]

HDV has a relatively low color resolution so you probably will run in to limitations.

Can you output the alpha channel from your key as a grayscale clip? That way you could add a slight blur and choke it a bit and stuff, then re-apply it as a travel matte.

 

[MovieCutter]

What is the source footage? If it's DV then you are going to run into the limitations of the codec pretty fast. Also, if you work in an uncompressed environment (even if you are working w/DV footage) you'll get a little more headroom w/regards to tweaking the footage.


Lethal

What Lethal said

 

[killmoms]

I was under the impression that all operations in Motion were performed outside of the limitations of the codec and simply rendered back down to the codec of choice when done. In other worse, the key operation would be working on a 4:2:0 color space image but the operation itself would be free of said limitations, and only the rendered result would be crunched back down to 4:2:0 on output.

 

[lilnyc]

I'm almost there. Thanks, everyone.

Here's my latest issue -- lumpy edges. I found a way to get rid of the green around th edges, and the key actually looks fantastic compared to what I did earlier. But now I'm concerned about this slightly rough edge (right). The original looks very sharp (left), and I want to emulate that:

 

[bigbossbmb]

In other worse, the key operation would be working on a 4:2:0 color space image but the operation itself would be free of said limitations, and only the rendered result would be crunched back down to 4:2:0 on output.

That is correct, but that original image is highly compressed and doesn't hold very much color information compared to an uncompressed (4:4:4) source.

 

[AviationFan]

I'm almost there. Thanks, everyone.

Here's my latest issue -- lumpy edges. I found a way to get rid of the green around th edges, and the key actually looks fantastic compared to what I did earlier. But now I'm concerned about this slightly rough edge (right). The original looks very sharp (left), and I want to emulate that:

Actually, the edge on the left appears softer to me than the edge on the right, which I think is why the one on the right looks unnatural. Have you tried feathering the edge? Just use a tiny little bit of it, you don't want it to be too soft. Other than that, don't expect perfection with DV/HDV footage.

Oh, and if you have Shake, check out this tutorial with Andrew Shanks:
http://library.creativecow.net/articles/shanks_andrew/preprocessing_for_keying.php
I've used this with good results in the past.

- Martin