Friday, 9 November 2012

Green Screen Experimentation

So, I plan on using the green screen for the performance element of my I Am... All of Me video. This is because I intend to make use a background which using some creative lighting effects to represent the confusing of the character as they try to choose whether to take the pathway towards being a brave-hearted hero or the pathway towards black-hearted evil.

Before I can start planning which shots I should use for the storyboarding phase of production, I need to know what is technically possible with the green screen in school. Because of this I thought it'd be a good idea to film some test shots from different angles to see what works well post-editing. There possibly are some obstacles I'll face as the green screen in school is very small - however this is a challenge one must face when they don't own a film studio.

Therefore, here is nearly two minutes of me acting like an idiot in front of said green screen (with backgrounds I happen to have saved on my computer - don't ask):

Many thanks to Mr. N. for sticking around after school to act as cameraman!

What worked well here then?

Static shots (where the camera stays in the same place) seem to work fairly well, though there are still some green reflections over my body. I'm guessing this is down to the lighting in the room at the time, but I may have to experiment more to pin down the exact cause.

As for what is in the shot itself, the first three shots show that I can get away with -some- movement myself, with only minor chroma keyer glitches showing through (usually near my hair and fingers). I did have problems with shots where I moved a lot though - there was one shot we attempted which featured me walking from outside of the shot straight past the camera, however this ended up being completely unusable when I tried editing it in iMovie. Because of this it will be necessary to keep the movement limited during the performance scenes.

Shots where the camera moves are a different story though; as we can see in the shot at 0:40 where Sir tried rotating the camera, the chroma keyer software struggles to keep up with it (resulting in some unwanted background and some moments where it clips through my jacket), which seems to be down to the way the visible lighting appears to change as the camera moves. This is also apparent in a later shot where Sir tries to pan the camera past me.

The very close up shot doesn't work on the basis that the software struggles to cope with the extra detail of my hair against the background, which makes the cut look like a bad magic wand job.

Because of this I should avoid using unnecessary very/extreme close ups during the green screen parts of my video - some will be necessary (Goodwin's conventions; plugging star image etc.) but I don't want to overkill it because I'd hate for my artist to be associated with terrible visual effects. I also still need to sort my eyes out, as we can see in the screenshot above.

Getting the chroma key to work in iMovie was a tad fiddly; most of the shots didn't want to work off the bat, so I had to reduce the Green Gain in the Inspector until it looked right. There was no formula for each shot, I just had to tinker until they worked. This could be annoying.


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