1.4 Green Screen OHP

OHP? Yes, Over-Head Projector

The idea behind green-screen videos is similar to that of an OHP.
The green layers become transparent and we can build up an image with multiple layers.

Choosing a Colour to be Transparent

Hosts cannot wear green clothes in front of a green screen.

The clothes will be made transparent.

In green screen movie production, a special shade of green (or sometimes blue) is used as a background, which is later made transparent during video editing.

Edited Videos are Layers of Videos

Think of "video tracks" in a video editor like the clear sheets of transparencies.

The final image we see is when the transparencies overlay on each other.

The difference is that the videos can move and change over time, whereas the OHP transparencies are static.

Example: 3-Layer Video

In the first 5 sec, spot at least 3 video tracks:

1. Top Layer: the title and logo of the video "Why PCBS are green" at the bottom corner

2. Middle Layer: an A-roll of the presenter recorded in front of a green screen

3. Bottom Layer: a static purple background image. The background is swapped out for an image of a circuit board at 4 sec.

7 sec: a single-track B roll

9 sec: another single-track B roll

[19 sec]
[original video]