chroma key

Damian Vicente · May 17, 2008

In three weeks i'll be shooting a short film, in MiniDv (with a Panasonic dvx100). The story takes place inside a moving car (at least 75% of the shots), and it is necesary to have good exposures both inside the car and the background.

In order to make the production easier, we decided to use a chroma key and have the car still. This method would allow us to use different exposures (assuming the different ammount of light) for the inside and the backrounds, (which, given the extremely short budget we're using, is very useful because it allows us to work with little light on the people inside the car). We are planning to light up the interior of the car with mirrors and white surfaces reflecting the sun's light.

The exterior shots will be done in a "traditional" way, with the car on the road and we'll be using natural light.

This will be my first time using a chroma key. Which considerations you recommend me to take in order to minimize any trouble I might have?

thanks a lot for any comments and suggestions.

d.

Edited May 17, 2008 by Damian Vicente

Walter Graff · May 17, 2008

Use green if your talent will always be lit spotty and darker than if they are lit by bright sunlight scenario.

Have at least 20 feet between your screen and the car from behind (can be closer if from teh side), and then make sure the screen does not cast unwanted incident reflections in the car.

Light your screen so that it registers about 50-55 units of luminance on a waveform if green. If you don't have a waveform, shoot then dump to tape and use your editors waveform to see the luminance level of the screen to see that is is in that range.

Remember that the inside of your car and your talent has absolutely nothing to do with the screen. It is a separate element from anything and simply needs to be light evenly. Light your talent for the backplates.

Some folks forget that glasses from the side often show up color behind them as in a screen shot from the side view. Green in the glass can cause problems. Make sure you do not have this problem.