Chroma keying on miniDV

TL07 wrote on 3/4/2008, 8:43 PM

Hi, I'm trying to use a video I shot on my jvc gr-d375u camcorder (miniDV) with a light blue background (all relatively the same colour) as my "bluescreen", but I can't key out the entire background without losing most of my image. The rest of the set is mainly green, but on the video, everything is very close in colour. Is there a way to use vegas to make bigger gaps in colour differences and then chroma key? Or should I try to reshoot the video with better lighting?

Comments

johnmeyer wrote on 3/4/2008, 9:23 PM

I wish the forum search engine was working. There have been many references in the past to an excellent tutorial on how to key DV. I think it is over at VASST. Ed Troxel's site (jetdv) may also have something.

John_Cline wrote on 3/4/2008, 9:42 PM

It would probably help if your blue background was more saturated.

rs170a wrote on 3/4/2008, 9:47 PM

Take a look at Keith Kolbo's excellent tutorial Using Chroma Key and Chroma Blur in Sony Vegas.
Substitute blue for green and (hopefully) you'll be OK.

Mike

farss wrote on 3/4/2008, 9:53 PM

One think to keep in mind is only the part immediately around the talent matters. The rest of the frame you can easily get rid of using a garbage matte i.e. a mask e.g. Vegas's beziers.

Bob.

Cheno wrote on 3/4/2008, 10:05 PM

This is a great plug-in for isolating and saturating colors -

http://www.moosehill.se/

The trick is to get your blue as saturated as possible. It's probably too dark as you're keying into other tones in your image. - if you turned on your vectorscope in Vegas, you'd want to be between 65 and 75 ire on your background. It will look VERY bright. So you want to turn up the saturation on the blue to get as close to this as possible. Ideally you want to do this in cam when shooting but this is a workaround after the fact. Watch for any blue other than the screen in your shot though too as this will effect it.

Then follow Keith's tute on applying chroma blur prior to the chroma key fx. Hopefully this will give you a pretty good key.

On trick for reducing green / blue spill (if you get it) is to create an alpha mask and used this to cut out your subject, then you can apply the aav6cc effect and desaturate the blue around your subject. This tends to help spill around hair or on the face. Not true despill but if you're using only Vegas, it works fairly well.

If you're really in a quandry, I'd be happy to take a look at a frame of your footage and send you back a .veg file.

cheno

TL07 wrote on 3/8/2008, 10:26 AM

Thanks for all the help, everyone! I'm sorry I took so long to reply; I thought I had email notification set up here, but apparently not... Anyway, I'll try to use that plugin first and if that doesn't work I'll post a frame capture or something.

TheHappyFriar wrote on 3/8/2008, 10:37 AM

also try cinecob's keyer ([url=http://www.cinegobs.com/]). Very handy & i've found if I'm having trouble in vegas that might handle it better.

jazzmaster wrote on 3/8/2008, 9:40 PM

Why Blue? Is Green out now?

VMP wrote on 3/9/2008, 10:31 AM

Reply by: jazzmaster
Date: 3/9/2008 6:40:38 AM

Why Blue? Is Green out now?

-------------------------------------------

That depence on what color you prefer to be made 'see through'/ transparent.

For example If you have an object that is green in color in front of the green screen, then both would become invisible.

So unless you want this to happen it is best to choose a BG color that has nothing in common with the object in front of it.

Theoretically you could use any color.

You are just programming the ‘chroma keyer’ to make a specified color’ ‘see through’.

But some colors are very sensitive for the common video camera, causing the different colors in the footage to bleed.

Red being one of them.

This will cause terrible outlines around the object that is cut out.
Because there are no tight borders between the colors.

VMP