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Calibration and Colour Management

While grading, one is looking at the picture on a display - a monitor or a projector. It's a digital representation of the original negative. A digital negative. What is needed is a system that ensures that the picture that one sees on the display is exactly what is printed on the negative. This is the Colour Management System or CMS.

And then there's calibration. Different displays behave differently even the same display behaves differently over time. Calibration ensures that the display shows the same picture through the course of its life. And one or more displays in the same facility show the exact same picture.

Colour management

There are two types of colour management systems. Hardware-based and software-based.

In the hardware based systems like Truelight from FilmLight, there is a hardware box that sits between the gradng system and monitor or projector. This stores'profiles' to simulate the behaviour of certain film stocks and certain lab chemistries.

In the beginning on needs to build these profiles. What is done is simply to expose test material, have it processed in a lab, then measure the density at various set portion of the frames, and enter these values into a computer. Then the same image that was recorded to film is played back on the monitor or projector and a probe measuers values off the screen.

So the system compares the image on film to the same on digital screen to arrive at the change it undergoes. It then applies the measured offset to all images. So what you see on a screen through Truelight is exactly what will record to film neg and what the audience will see in a print.

This is a simple explanation. Actually its a bit complicated than that. But this is the principle.

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