I've got a video of me juggling a soccer ball. The camera stays completely still the entire time, and I've even got shots of the background without me on it.

I've never done any real video editing, but it seems a simple subtraction of the background from the frame would be pretty simple. Basically, I'm asking if I can use the background as a greenscreen.

I suppose the most obvious question is, is the background green or any other solid colour?

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Better than a poke in the eye with a pointy stick any day...

You might get somewhere with this if you are lucky. Not tried it so just thinking on my feet but...

You will need a decent piece of compositing software. Somethign like Adobe After Effects (not cheap).

In order to achieve a decent enough matt you could aply a difference mode to the two layers. What's left should be either the bits that are different or the bits that are the same. Like I said, never tried it so it might work either way. The resulting image will have either a large blasck or large white area of the bits that are the same.

Take that result then apply levels adjustments to it to puch the remainder all the way up to black/white (the opposite colour). This result shou odbe a decetn matt for your footage so just add your orighinal footage again and apply what you had a track matt.

Easy lol

Of course this will ONLY work if the background is exactly the same in both pieces of footage. If there are trees then they will lkely have moved in the breeze and so (to the PC) will not look the same.

Alternatively, still in a good compisitor import your footage and rotoscope a mask around yourself in it. That's what I had to do last time I needed to do this kind of thing. Takes ages, keyframingit for every frame but you do get decent enough results. But then again, I only had a few seconds of footage to key.

Good luck.

Alan

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