In association with HPA's 2008 Technology Retreat
Synopsis:
Video, HDTV, and digital cinema all start with scenes that generate or reflect light, and end with images made from light generated by – or reflected from – a screen. So, it is useful for video, HDTV, and digital cinema engineers to be familiar with light measurement! In this seminar, I will introduce the measurement of light in physics (radiometry), and the measurement of light useful to vision (photometry). I will explain units of light measurement such as lumen, lux, and candela per meter squared ("nit"), and explain how to convert among them.
The units of radiometry and photometry are directly useful to understand image display, particularly projection. However, it is also interesting to relate these units to the amount of light available in a scene, and then to the fraction of that light that is available to a camera that is acquiring an image from the scene. I will explain how radiometry and photometry are related to camera image sensors, to camera sensitivity and dynamic range, to camera signal processing, and to image quality.
Video, HDTV, and digital cinema cameras have always been based upon sensors producing signals proportional to light energy; however, until recently it has been common practice to use circuitry in the camera to map those "linear-light" signals into nonlinear values. The mapping has been necessary to impose perceptual uniformity (to overcome a limited number of bits), to impose picture rendering, or both. Emergent cameras make it possible to acquire scene-linear data directly, and emergent capture workflows often invert the cameras' mappings to make scene-linear data available at the first stage of post-production. We will explore the consequences of these innovations. OpenEXR is an emergent coding system that facilitates scene-linear data handling and colour transforms; we conclude by exploring OpenEXR and its colour handling.
Audience: This seminar is appropriate for technical professionals who are experienced in creating and manipulating color imagery for SDTV, HDTV, or digital cinema. It is also suitable for programmers and engineers. WARNING: Many graphs, equations, and diagrams will be shown.
Materials provided: Course handouts will be provided. Portions of the seminar will be based upon Charles Poynton's book Digital Video and HDTV Algorithms and Interfaces.
Fee: USD 175. Register at the HPA site.
Charles Poynton -
Courses
& seminars
2007-12-17