Halo problems / Green screen / HVX 200

E

ewalden

New member
I just did a test shoot a few days ago with an HVX 200 in a green screen studio.

I have been running the results through some keying programs, and have been getting funny halo problems.

I'd like to figure out what the problem is so that I can correct it for the real shoot in a few weeks.

I shot to P2 cards. I then used Raylight Raymaker to convert the .mxf files to .avi files so that I could work with the footage in After Effects.

Finally, I used the Primatte Keyer to generate my matte. The results were really good, except I would get an outline around the foreground images.

I took a closer look at the original footage, and there is a bright outline around the edges of the foreground image.

If you take a look at the attached image, and blow it up to 200% or 400%, you'll see it.

So, rather than having an edge transition that goes from black (the color of the actors' clothing) to green, it goes from black to almost white-green, to green. So, the keyer gets rid of the green, but not the faint white line around it.

The result of all of this is that the composite looks very good against a light background, but terrible against a black / dark background.

I am wondering if this could be due to some camera setting like edge enhancement, or is this a typical lighting problem?

I have a frame grab PNG file at:

http://ewc.securesites.net/rawframe2.png

Thanks!

- Eugene
 
Yeah, there is some edge enhancement going on that's seems to be the problem. Otherwise that's a perfect green screen shot, no fault of yours, I think its a camera issue. Try dialing down the sharpness, then sharpen the composited image as a whole later.

Everyone doing key work deals with edge in some way, at any level, its easy to pull a good key on the rough solids, but there is always a battle when it comes to edge. Everyone has their own tricks, slider recipes, etc. It basically comes down to hours and hours of massaging the key, double matting, whatever trick you can do to make the final composite happen.
 
I have no experience with the program you mentioned so I cannot give direct advice. I use Adobe After Affects and you get that all the time when importing footage. If you are compositing something over a green screen and get a halo effect, you ned to single-out the layer being moved in (the one with the halo effect) and then apply the Remove Color Matting Effect to the layer (not the composition) and change the background color to the color that the layer was originally saved to (usually black or white).

When you import footage into After Effects, you need to make sure that the Alpha Channels are properly interpreted by the program which is something that you can set.

I don't know if this helps at all, but I hope it does.
 
I think you could try to light the green backround just a bit less. To bright background can mess up the edges.
 
The HVX is a 4.2.2 camera which means that colour detail is getting a little bit smushed so some fringing is bound to be part of the comp headache. That plus inherent chip rez means some software post assistance might be necessary

You could, for future, try lighting down the greenscreen a bit (but watch for the other HVX prong - Noise)

Another thing you might try is Composite wizard (its fantastic for green screen cleanup and edge work) http://www.redgiantsoftware.com/cowi.html
 
I don't know if this would help with your problem or not, but I know it's recommended to backlight your subjects with magenta to balance out the green reflecting onto your subjects.
 
Keyed fine for me, I just stuck them in here with some crappy CC and stuff:

keyed.jpg


- Kyle
 
Thanks for the replies

Thanks for the replies

Thanks to everyone for taking the time to reply.

Kyle-- you are getting the same key results as me. It's almost perfect, but if you look at where the foreground subjects are composited atop very dark backgrounds, for instance, where her right shoulder overlaps Leo's dark coat, or where his back overlaps the dark building, you'll see a fine white line that goes around the subject.

So, for now, I've just been setting them on light backgrounds, and it looks great.

However, I'd love to figure out how to shoot in the future so that I don't get that white outline, in case I want to set the subjects on a really dark background.

So far, my best guess is that I need to lower the detail settings on the HVX-200, as someone else has suggested.

I asked my DP what settings he had used for the shoot, and he said that it was the fourth factory preset scene file.

From what I can tell, this scene file has a detail setting of 0. Next time I rent the camera, I am going to try successive tests, cranking down the detail as I go, to see if the apparent edge enhancement goes away.

Also, thanks to James Mather for the suggestion of using Composite Wizard. Those tools really complement Primatte very well. I think I can get rid of the white line by using the Alpha Cleaner tool (not sure why, but it works). The Background Smoother is also an amazing utility.

- Eugene
 
Hey I found that using an adjustment layer with levels switched to the alpha channel and taking the input black to about 15% really helped your footage. I use keylight. Just a thought... Cheers Glenn
 
You're welcome Eugene.

yep - composite wizard is indispensible. The edge blur (where it just blurs the matte a set amount of pixels is also often very useful - making for a very organic key (only a couple of pixels mind you) - gets rid of that cookie cutter effect.
 
Shibuya Oboya said:
I don't know if this would help with your problem or not, but I know it's recommended to backlight your subjects with magenta to balance out the green reflecting onto your subjects.
Click to expand...

I agree. You have no back or rim lighting on the actors in this shot and the green is bleeding on to the edges. Not neccesary to use magenta backlight but it does work.

Screen could be a little close and a liitle hot also. Both will cause problems of bouncing the green.

Btw: why did you use green and not blue?
 
The Videocopilot tutorial looks nice, but isn't it using Keylight's $5000 plug in and not just After Effects?
 
Bherr,
I'm not very familiar with after effects but hope to be soon enough. yes they are using that plugin. I wasn't sure if it came with after effects though. but I found this.
http://www.thefoundry.co.uk/pkg_purchase.aspx?ui=A5FB8E97-D752-4E01-AC7D-17B39B7E1192
it looks like its only $395 for a permanent license locked to a computer or
$592 for a floating license for a network setup.

But please correct me if I'm wrong.

edit: looks like the software plugin for Discreet is $2500 for a locked and $3750 for a floating. I'm assuming discreet is a hardware based NLE that cost tens of thousands.
 
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