Session 6: Chroma Keying 22/03/13

 

Chroma Keying

Today we were introduced to Chroma-keying which is the layering of green screens. This is done to remove the white fuzz that often appears around actors in front of a screen, such as on Flash Gordon.

300 was the first film that was filmed completely on green screen, with no location filming.

To ensure filming on green looks good you should use Chroma paint, or the correct blue or green colours. If using material then it should be totally flat with no creases which can cause shadow, which can also be caused by uneven lighting.

In a group we attempted to film on Zu3D using basic green. Using a piece of green felt draped over a flat brown piece of cardboard, we attempted to make the surface as flat as possible so that we would not have any shadow. However, even without a character on screen this proved difficult because of the light. Firstly we was in a room with inconsistent lighting, with 8 room lights, some on some off which threw the balance off. Secondly there was many people in the room constantly moving which meant the light was constantly changing. This gave the light on camera a sort of "jumpy snowing" effect. To counter this we put a lid on top, thus blanking out the lights from above. As we could not stop people moving behind we had to ensure that the camera did not move to create a still as image as possible, whilst positioning ourselves in the same position for every screen shot. When we thought we had a flat as possible back we introduced a white horse which didn't blur too much. We then took away the green background using the Zu3D function which left an almost plane black background with minimal snowy effect.

Session 4 : Introduction to Stop-Motion Animation

In our last session we used Zu3D to film a short animation using stop-motion. Our group, myself, Arfyn, Ceri and Andrew used toy cars and figures to create a street traffic scene that had an out of control skateboarder causing havoc on a street.

The intention was to have traffic moving up and down a busy street, by using many cars moving on the road and disappearing in and out of the shot. A skater was to be introduced into the road to make the cars swerve and take the onscreen action from linear and smooth running into a very visual experience with lots of movement.

However, the animation took longer than expected, it was very time consuming and required many intricate small movements of the pieces to create the effect of movement.

We found that a slight error or unexpected movement can cause a very visual problem on screen. For example: If you are to pick up a piece of the animation and put it down in the wrong place, it can be seen as “jumping” on screen. We had to work out how many frames should be used per shot, the speed to the action coinciding with the intricacies of each movement. Due to time constraints we did not finalise the sound, and this has shown in the final video.

Original Video - More videos at TinyPic

Despite this, our initial difficulties were no more than expected for using a new piece of kit. Zu3D was fairly easy to use on screen, with its simple frame boxes and layers for sounds and effects.

After this first use I will be considering this for our final animation.