RED One-MX Greenscreen Keying Problem on Hair

[Daniel Broadway]

Hey guys. I am having some trouble with a recent greenscreen shoot we did on a RED One-MX. We shot at 4K, and I am not using any OLPF Compensation or sharpening of any kind, nor scaling. However, I'm getting artifacts that are very reminiscent of edge enhancement on other camcorders. Now, as I understand it, RED does not edge enhancement.

I have posted examples below to illustrate our problem, as well as a frame of the R3D in hopes someone can give me a clue as to what is going on. Luckily for this shot, the talent will be composited over a light background, and so the edge problems will be hidden, but if I had wanted to composite this shot against a starfield, I would have been out of luck. The shot used a Zeiss Super Speed Mark III, if that makes any difference.

EDIT: Please Right Click and open Images in a New Tab to view at Full Resolution.

Original Plate

Keyed Against Black. Note the horrible artifacts around the hair, which reminds me of keying edge enhancement artifacts.

1:1 Crop of the key.

The Alpha Channel, which looks pretty good.

Red and Blue channels at 1:1 crop of the original 4K (Saturation boosted to 1.7 to view problem easier)

Red channel with a Miminum De-Noise/De-moire which really shows the problem on the hair. (Saturation boosted to 1.7 to view problem easier)

EDIT: Please Right Click and open Images in a New Tab to view at Full Resolution.


Here is a link to the R3D for download. Please offer any advice you can on the matter. Thank you.

http://www.makevisual.com/download/L_r3d.zip

 

[Alexander Ibrahim]

Before I dig in ... this is actually fine.

I saw The Hunt for Red October today ... they wish they had keys this good on that film.

The thing that jumps out at me is that the image has a green tint.

You should give it a whirl first giving the image a proper white balance. I tried this, and it didn't fix the issue, but it led to more pleasing results - including the preservation of her eye coloration.

As far as your edge enhancement problem, I don't see that. I do see a bit of CA and vignetting ... typical of MK3 lenses.

I also see hair doing what hair does ... basically screwing a key up as usual. Being a scrim and a reflector all at once ... you know true evil.

Well maybe someone else has more interesting ideas on the issues here.

I will say, I'd comp this against a starry sky. I've had to comp worse against starry skies, and its been a good result.

I'd be more worried about the chroma green hand and the spot on her right breast.

 

[Paul Leeming]

What keying software are you using? They are not all created equal....

That said, the R3D looks perfectly ok to me.

HTH

Cheers from Tokyo,

Paul

 

[Jose Lomeña]

I like your matte, how do you extract it?
I think the "artifact" problem come from camera compression. You can try with redcode42, or epic 3:1. You can get better gamma with redgamma2. In the other hand your background will be black?, i think is better to see results with your real background.

 

[Hans von Sonntag]

Daniel,

I've done tons of GS work with the RedOne. It does the job equally as good as 35mm (or even better) as long as you don't lift the noise (expose fat at 320 ASA) and use CA free lenses. Super Speeds are not that bad in this regard, BTW. Develop at 5000K even if you shoot under tungsten (use 82C there), use Recolor2/sRGB and RedlogFilm or RedGamma2. No sharpening, no noise reduction, no OLPF compensation.

The footage that you show looks fine so far. Very even GS.

The problems that you have are probably located at your keying software or the skills of the operator. There are huge (unbelievable huge) differences between AE out of the box and e.g. Autodesk's Modular Keyer in conjunction with a seasoned artist.

The matte that you provided is not fully pulled. There are opaque areas where there should be solid parts. The hair, however, looks fine, probably too thick though, creating slight white boarders. In the 2012 Modular Keyer in Flame and Smoke is a new node called Pixel Spread. This fixes many issues in this regard, especially when it comes to luma keys and sky replacements.


Hans

 

[Daniel Broadway]

I very much appreciate the comments so far. However, many of you are saying you don't see a problem with the original footage, and I don't understand how that can be. Are you right clicking and viewing the examples at full res? The edges on that key are clearly not very good around the hair under her chin. The red and blue channels clearly have a weird ringing-like artifact around the hair strands. Look especially at the ringing artifact on her chin in the Blue Channel. I am the person who pulled the key, and I've been doing greenscreen for 10 years, and never had this problem except where edge enhancement was involved.

I agree it could be some weird CA or vignetting issue, but I wanted another set of eyes to indeed confirm or deny that suspicion. I disagree that this key would be acceptable against a dark background. To anyone looking at the R3D, the artifacts will not manifest themselves until you raise the default saturation to 1.7 or so, but the keying software is indeed seeing it, and having a problem with it. I've tried keying it with Keylight, Primatte, and Ultimatte, to the same result each time. Again, any extra advise would be greatly appreciated.

To fully reveal the problem, I have included a 1:1 crop of the footage, and how the key looks up close.

 

[Jeremy Wiles]

I've keyed a ton of footage and have worked with much worst in the past. You just need to adjust your "Clip Black" to about 35. Here's what I would do:

1. Color correct the footage in REDCine. It looks like you may need to increase your blue channel. Watch your historgram.
2. Use After Effects Keylight and get a key with the color picker as close to the subject as possible.
3. Set the Screen pre-blur to 1 or 2
4. Under View>Screen Matte adjust "Clip Black" and Clip white accordingly (35 black and -75 white). Check results by going to View>Final Results
5. Add "Simple Choker" to remove the line around the edges (might not be needed)
6. This is going to add some grain, so apply the effect "Remove Grain" and adjust it accordingly.

Hope this helps.

 

[Hans von Sonntag]

Brian,

Your picture shows an already pulled key on a black background. Most of the artifacts one sees are introduced by the keying process, some perhaps by the camera.

You provided a link. I will download the file and give it a try.

Hans

 

[J Davis]

one trick is to use a curve pull green gently out of the whole image before keying, this increases the separation between greenscreen and girl.
Then add it back after

 

[Mark Wilkinson]

What format is the footage you are keying?

I did a quick key from you r3d footage and didn't have the same problem. If you are using Prores4444 or DPX or 16bit tif, then this isn't the problem, but if you are keying 422 footage or less it will make matters worse.

BTW, what software did you use to grab those images?

 

[Daniel Broadway]

What format is the footage you are keying?

I did a quick key from you r3d footage and didn't have the same problem. If you are using Prores4444 or DPX or 16bit tif, then this isn't the problem, but if you are keying 422 footage or less it will make matters worse.

BTW, what software did you use to grab those images?

We usually export Linear EXRs out of RedCine and key in After Effects. However, I've brought the R3Ds directly in, and this artifact was still in the red and blue channels. If you did not have the same problem, could you please post a 1:1 screen shot of your key against black. I'd be interested in seeing your results. As for grabbing the images, I just did a Print Screen and cropped in Photoshop.

 

[Hans von Sonntag]

You provided a link. I will download the file and give it a try.

Hans

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Download the .zip (12 MB)

You will fin two DPX files that show a low-key result and an high-key result, both worked very well, IMHO.

The problem most people have when pulling keys and hair is that the de-spilling is much to lightly (luma too high) done and hence will introduce artifacts that are not found in the footage. I used Autodesk's Modular Keyer and comped quickly in Action.

There is nothing wrong with your footage, IMO.

Hans

 

[Hans von Sonntag]

The thing that jumps out at me is that the image has a green tint.

This is logical. You shoot in a green environment. You call that green spill. It's usually all over the place and you have to de-spill it alter AFTER you pulled the key. There is no need to WB GS footage. On the contrary. You want it as "un-processed" as possible.

Hans

 

[Mennovandijk]

I encounter similar problem with your footage/image using keylight


I pulled an image from a shoot last week I did, and used keylight and tweaking it a little and get this:


Keeping tweaking I don't get is as clean as the second image while your image seem to look fine I don't know why this happens

perhaps a small backlight would have helped to pull a better key?

 

[Hans von Sonntag]

...If you did not have the same problem, could you please post a 1:1 screen shot of your key against black...

The best compositor with best GS footage will never able to pull a key against black that will not look artificial and full of artifacts. Keys must be tackled differently according to the BG. There is no such thing as the perfect key, only makeshifts that work well in the particular situation.

Hans

 

[Daniel Broadway]

The best compositor with best GS footage will never able to pull a key against black that will not look artificial and full of artifacts. Keys must be tackled differently according to the BG. There is no such thing as the perfect key, only makeshifts that work well in the particular situation.

Hans

I don't understand how that can be. Could you elaborate as to why you cannot put a black background behind a greenscreen key. I've seen it done many times in sci-fi movies against space backgrounds, so I'm inclined to question this.

 

[Mark Wilkinson]

I think what Hans means is that you need to tweak the key to make it look good on black.

For instance if you reduce the brightness in you edge color correction, it will make your edges go black instead of gray. Then it will look correct over the final frontier. If you then put it over a white bg, it will look like it has a nasty black edge.

 

[Hans von Sonntag]

I think what Hans means is that you need to tweak the key to make it look good on black.

For instance if you reduce the brightness in you edge color correction, it will make your edges go black instead of gray. Then it will look correct over the final frontier. If you then put it over a white bg, it will look like it has a nasty black edge.

Couldn't have said it better!

Thanks, Mark

Hans

 

[Daniel Broadway]

I pulled this key on black in literally 15 seconds. I can put every shade of white to black behind it and it composites perfectly.

 

[Doug Beatty]

Another way to go in AE would be to create a holdout matte that isolates the hair on a separate layer.

Once the hair matte is keyframed to your liking, duplicate that mask back onto your core matte and change it to subtract. Then on the top 'hair' layer, change the mode to Alpha Add and you'll rid yourself of the gap that is left between the two masked out layers.

Now you'll have two separate mattes with Keylight applied to both and you can fine tune the key on the hair and adjust your choke/blur values on only the hair.