Truelight - FilmLight · Truelight is a complete colour management system for pre-visualising film and HD images on electronic display devices, working equally well with digital projectors

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Truelight

Truelight Primer

Truelight

Document Reference: FL-TL-TN-0369-Primer

Document Version: 1.1

Modified: 27/01/2010 15:02

© FilmLight 2010

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Contents Truelight Primer

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ContentsChapter 1 - Introduction 1

Chapter 2 - Cube generation 3Why use a Truelight profile instead of a LUT? · · · · · · · · 4

Chapter 3 - Cube application 5Truelight SDI (hardware) · · · · · · · · · · · · · · · · · · · 5Truelight application (software) · · · · · · · · · · · · · · · · 6Truelight plugins · · · · · · · · · · · · · · · · · · · · · · · 7Embedded Truelight · · · · · · · · · · · · · · · · · · · · · 7

Chapter 4 - Calibration 9Display · · · · · · · · · · · · · · · · · · · · · · · · · · · · 9Environment · · · · · · · · · · · · · · · · · · · · · · · · 10

Chapter 5 - Other Truelight products 11Truelight On-Set · · · · · · · · · · · · · · · · · · · · · · 11Truelight Library · · · · · · · · · · · · · · · · · · · · · · 11

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Contents Truelight Primer

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Truelight

Introduction Truelight Primer 1

1 - Introduction

Truelight is a complete colour management system for pre-visualising film and HD images on electronic display devices, working equally well with digital projectors and computer monitors. Truelight enables artists, colourists, cinematographers and directors to review, accurately, the final look at any point in the digital post-production process—reducing film-outs, matching and rework, and saving valuable time.

Truelight has been developed with a clear understanding of colour science and is supported by some of the world's foremost colour scientists at FilmLight. It provides a full simulation of the entire workflow from digital data to the final projected image. By carefully measuring and characterising each stage in the workflow, the closest possible match between preview and final image can be achieved.

Truelight does not require an explicit model of the processes in the workflow. It characterises the steps by carefully measuring the inputs and the outputs for each stage in the process for selected colours throughout the colour space. These calibrations are then combined to form a three-dimensional colour cube through which the images are viewed.

Because Truelight is not restricted to a particular physical model of the film process, it can be extended to simulate unusual film stocks, printing via an intermediate stock, or bleach bypass. It can simulate over-exposures and under-exposures in each colour, and can also highlight colours that are not achievable on different media.

The Truelight system is modular and extensible, allowing it to scale from a single system to a complete studio. It allows management and adjustment at any level of complexity: from the simplest of technical requirements to the most exacting.

To understand the Truelight system, you need to look at the three major stages of the process: cube generation, cube application and calibration.

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Figure 1-1: Truelight overview

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Cube generation Truelight Primer 3

2 - Cube generation

The three-dimensional colour cube is generated by the Truelight software library, which uses a set of calibrations (for film processes, displays, and so on) and other settings; calibrations are discussed in Section 4 - Calibration starting on page 9.

Settings for specific projects and environments are saved in a named profile, and are then implemented in software or hardware as described in Section 3 - Cube application starting on page 5.

A profile combines the calibration data for recorders, printers, cameras, lamps and displays on each machine on which it is being applied. The profile makes it easy to implement consistent, facility-wide management—each workstation simply needs to supply its own display calibration, and has some latitude for ‘tweaking’ the display settings if required.

You may require only a single cube, with periodic display recalibration, or you may need to use different cubes dependent on project, film recorder and film stock. Changing the profile generates a different colour cube.

Figure 2-1: Truelight profile

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Why use a Truelight profile instead of a LUT? Truelight Primer4

Why use a Truelight profile instead of a LUT?

You may have access to software that is capable of building lookup tables (LUTs). So why use Truelight profiles instead of LUTs?

Truelight profiles are more portable and flexible than LUTs and can drastically simplify large post-production projects that involve multiple facilities or many systems within one facility.

A LUT can only pair one input space with one output space. If the output space is an uncalibrated display then a LUT built for it (using some suitable calibration data) cannot be used for anything else. To use LUTs effectively, you therefore need to create a LUT for each specific display device. A LUT also cannot tell you anything about any input colours that may have fallen outside the output display's gamut.

A Truelight profile, on the other hand, is fully portable in that you can copy it to any system and it will use the local display characterisation to generate the correct LUT; you can then adjust the way the white point is dealt with depending on your display and viewing environment, and you can check for out-of-gamut colours at the click of a button.

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Cube application Truelight Primer 5

3 - Cube application

Once a three-dimensional colour cube has been generated, the image data is transformed through the colour cube before it is viewed on a display system. The cube does not alter the source data, but provides a viewing transformation.

There are four methods of delivering the cube transformation:

Truelight SDI (hardware).

Truelight application (software).

Truelight plugin—for example, for Apple Shake™ or Adobe After Effects™.

Embedded—for example, in the Baselight colour grading system or Truelight Player.

Cube transformations can also be used as part of the Truelight On-Set system, or incorporated into your own applications using the Truelight Library. See Section 5 - Other Truelight products on page 11 for details.

Truelight SDI (hardware)

The Truelight SDI unit provides stand-alone, real-time, accurate monitor calibration and print emulation on any HD display or digital projection system. It is a system-independent, reusable solution that can be permanently wired in to a facility, and requires minimal operator training.

The unit provides push-button selection for up to 15 colour cubes and a cube bypass.

For more details, see the Truelight SDI datasheet on the FilmLight web site.

Figure 3-1: Truelight SDI

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Truelight application (software) Truelight Primer6

Truelight application (software)

The Truelight software application applies the colour cube transformation to a single image. It is useful where occasional verification of colour is necessary, for example, against a reference image.

Truelight software is available for Linux and Mac OS X.

Figure 3-2: Truelight UI

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Cube application Truelight Primer 7

Truelight plugins

Truelight plugins are available for well-known compositing and VFX applications. These plugins operate in a similar way to the Truelight software application and can be used to visualise film images correctly within the specific application.

Currently Truelight plugins are available for Apple Shake™, Adobe After Effects™ (the After Effects plugin can also be used in Eyeon Digital Fusion®) and The Foundry's Nuke™.

For more details, see the Truelight Plugins datasheet on the FilmLight web site.

Embedded Truelight

Truelight technology can be embedded in applications, utilising graphics card hardware to achieve real-time playback through a Truelight colour cube. The Baselight colour grading system employs this technique, as does the Truelight Player.

For more details, see the Baselight datasheet and the Truelight Player datasheet on the FilmLight web site.

Figure 3-3: Truelight plugin for Apple Shake

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Embedded Truelight Truelight Primer8

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Calibration Truelight Primer 9

4 - Calibration

Measurement and calibration are required at several stages throughout the workflow. All of these calibration processes are recommended to ensure faithful calibration. FilmLight offers a full calibration service to create an accurate profile for any specific workflow.

The stages are: recording, printing, cameras, lamps, display and environment.

By combining the recorder, print, camera and lamp calibrations, an accurate and complete colour transformation can be determined. Given that this transformation is known, it is then possible to generate transformations for display devices to closely match the images in their final viewing environment.

Display

The electronic display, whether a monitor or a digital projector, needs to be calibrated. A CRT monitor is probably the most volatile element in the calibration chain, and requires periodic checking and adjustment to cater for drift with age or relocation. Not all monitors are suitable display devices for film imagery, but a level of fit can be achieved with most reasonable quality devices.

Truelight calibration techniques are non-intrusive, but require that the colour temperature, brightness and contrast of the display device are fixed. There are two methods of calibration: using a probe, or by eye.

ProbeThe Truelight Monitor Probe and Truelight Projector Probe work in conjunction with the Truelight software application to measure a range of grey and colour patches. The Truelight probes are high-precision instruments that are able to measure contrast ratios at up to 1:10,000, far in excess of other commercial devices. The calibration process is automatic and completely objective. For more details, see the Truelight Probe datasheet on the FilmLight web site.

Figure 4-1: Truelight Projector Probe

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Environment Truelight Primer10

By eyeThis method gives an approximation for tone curves and colour balance. If a probe is not available, this process can be used to set the tone curves by manually adjusting the level of different grey patches over a 10-stop range. It requires the Truelight software application and operator control to achieve a display calibration.

Both methods produce a display calibration that maps desired response to input RGB values. Note that this method is far more accurate than using graphics hardware LUTs to compensate for the display.

Environment

Ideally, images should be viewed in a blacked-out room. Whilst this is the recommendation, in practice this is often not feasible, and a range of viewing environments from office lighting to black-out will exist. Truelight provides user options that cater for environmental variations, including boosting the brightness of the display, or enhancing the shadow detail to simulate the appearance in a darkened room.

There are other diagnostic tools such as the gamut alarm that allows colours that are out-of-gamut for a particular display device to be highlighted.

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Other Truelight products Truelight Primer 11

5 - Other Truelight products

The Truelight product range includes a specific solution for on-set monitoring and dailies review—Truelight On-Set—as well as a specialist SDK toolkit—the Truelight Library.

Truelight On-Set

Truelight On-Set provides calibrated Truelight assurance to directors and cinematographers, as well as ensuring a clear and accurate communication channel for calibrated looks back into post-production.

Truelight On-Set is primarily used in two scenarios:

On-set monitoringFor monitoring while shooting, the Truelight On-Set system applies a cube transformation between the camera and monitors. Colour grades, set in pre-production or on previous shoots, can be applied and then further adjusted at the time of shooting.

Dailies reviewThe Truelight On-Set unit allows you to apply colour correction, performed by a colourist at a post-production facility, to footage as it is reviewed on-location. The production team can make further adjustments and send the new settings back to the facility.

Truelight On-Set is able to apply an input transform—useful when shooting with digital cameras in raw or wide-latitude recording mode, where it is often necessary to convert images into the colour space to be used for colour correction—and/or an output transform—to make the on-set display look as close as possible to the reference display that will be used for final colour grading and delivery.

Truelight Library

The Truelight Library is available for developers who want to incorporate Truelight functionality into their own applications, and for clients who want to create accurate Truelight 3D LUTs for use in other run-time platforms (such as projectors).

The Truelight Library includes training and directed development; additional programming and support services are available from our specialist team.

Contact [email protected] for more information.

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Truelight Library Truelight Primer12

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