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CAn I add a background to live footage outside of the studio?

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Dionne Knapp
CAn I add a background to live footage outside of the studio?
on Jan 28, 2008 at 9:23:28 pm


I am an intern Broadcast producer and I know how to do this IN the studio but I want to do it outside of the studio.
I have been doing an interactive "movie set" at local elementary schools for almost a year. The presentation has gotten pretty popular and i have schools calling me all the time now.
Last week a Junior High School called and begged me to do it for thier 7th & 8th grade classes.
I usually only do elementary and the kids get to "act" in a scene fron a pirate movie I wrote just for the presentation.

My 11 year old daughter and I agreed that Junior High Schoolers may find "Pirates" too "babyish". I decided I would have them "Film" a "Mucic Video " instead.

To make it look more authentic, I want to have a scenic background on the set. This is because the Cameras are connected to a big screen TV so the students and "Director" can see what the "Cameraman" sees.

The problem is, those large Muslim Scenic Backgrounds for film and theatre are EXPENSIVE!!! Like THOUSANDS of dollars!

I remember taking my kids to Chuck-E-Cheese pizza and they had a video camera with a "Green Screen". When the kids got in front of the camera and danced around, you could see the on the TV above- only with a different background!

I keep asking my friends how they do that but of course, they don't know.

Does anyone here know how I can ackomplish that same effect? I have the chroma screen and camera of course but what else do I need? A laptop? If so, what kid of software and cables and how do I connect everything?

Im sure its MUCH cheaper that buying or renting a cloth backdrop!

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Mark Suszko
Re: CAn I add a background to live footage outside of the studio?
on Jan 29, 2008 at 4:57:42 pm

Well you're asking a lot for nothing, but here are some suggestions, there are other ways to go as well.

You can use this piece of software:

with a windows laptop that has firewire and USB and a camcorder that has firewire and USB and a microphone input for better sound options (Canon ZR 800 I believe has this, about $150 at Walmart)

to do some simple chromakey work. The neat part of this software for educators is that it also includes slides and graphics as well as even a teleprompter function for reading long scripts into the camera. There will be a bit of a learning curve in using it, and it may not be able to do every feature "live" but only nearly so. Meaning you'll shoot onthe green screen but won't immediately see the substituted background until the computer renders a finished movie a few minutes to an hour later. Depends on the length of the shots and the power of the computer. Earlier versions of this product were made by Serious Magic inc. before Adobe bought them, and you might be able to find used older versions at a deep discount on ebay or the like.

In the pro world we obviously use much more expensive and sophisticated hardware and software, what I'm describing to you is certainly on the "low end" of what's out there, and when you play with the low end stuff stuff you have to make certain compromises and work-arounds.

To really be able to do it live, efficiently, usually the expedient way is to use an actual camera switcher that has the keying built in. The very cheapest one I know of that might be able to do this is an Edirol from B&H photo-video in NYC for 999 bucks brand new:

You might be able to find comparable or better switchers cheaper than this on ebay, perhaps a Panasonic or Videonics, but unless you are knowledgeble in such gear, or have a video friend who knows what to look for and look OUT for, likely you'll end up with a bad deal.

Assuming you have a switcher like the one above, you will need at least one camera to shoot the green screen, and an external source for the background image to be fed into the second channel. That could be a laptop, a VCR with pre-recorded images, a 30-dollar DVD player with a premade DVD or cd of source images, or even a cheap digital camera pre-loaded with the images and using it's video output cable to feed the switcher. Though those tend to time-out and go into sleep mode after five minutes just sitting.

You can chromakey with most any material and any color, but you make things easier if you use a very saturated and flat, matte colored green cloth. Lighting the cloth EVENLY is the single most important thing about chromakeying. One cheap way to do this is to shoot outdoors and use the full sun, but wind can be a problem. You have to keep the backdrop far enough behind the actors so that no shadows fall across it and no gree is reflected onto the actors. My rule of thumb is at least double the height of the tallest person to be shot.

Indoors, you will need to use soft lighting on the green screen. The cheapest thing there would be flourescent tube shop lights from a home center, or halogen work lights shining thru sheets of proper photographer's diffusion material or as a cheap alternative, baker's parchment(high temp resistance). The cloth must be lit evenly from edge to edge with no hot spots and no dark spots, or the effect becomes hard to make cleanly.

A good source for inexpensive but wide chromakey cloth is rosebrand in NYC:

You can find a bright lime green cloth at walmart or a sewing store that will work, but you'll have to sew it into wider pieces, plus come up with stands or ladders and pipe to hang it from. Gets to be kind of a big clumsy deal. An ideal cloth would be like the material in your car's headliner. Fuzzy enough to not reflect, stretchy enough to un wrinkle. I have successfully keyed on everything from the expensive $60 a bucket Rosco paint to $50 photographer's paper rolls to green and blue plastic picnic table runners with a matte finish from the Dollar Store. Pro materials are faster and easier to work with and control, plus give optimal results, so they cost more.

You might want to do some more research into techniques before plunging ahead. Google these sources:

videouniverity forums

for more on chromakeying in the field. I have done stuff like this for school tour groups many times and it is always great fun for all. The kids use the camera and switcher to put their heads on each other's or the teacher's bodies or onto tape of dancing puppets, we shoot from above looking down with cloth on the floor as they stand on one foot and pretend to be flying or in zero gee. Make them giants or teeny tiny figures perched on a shoulder or in a hand, make clones that talk to each other... Stuff like that. Good times.

"Oh, you wanted to RECORD that?"

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