HDRI and Photography

With today’s typical hardware, it is not possible to capture a lighting design project in a single shot and get it represented accurately on screen “as-is”.  Accurately meaning “how the eye perceived the project at the time the photo was taken”.  Typical digital display devices cannot display the entire range of luminance that a human eye can perceive. Cameras can’t capture that range of luminance at a same time either.  In technical terms, that is the complex (and how interesting) world of Tone Reproduction or Exposure.

For example, your eye adapts rapidly to a variety of contrasts and your brain condenses all this into a unique image, as if you would apply different brightness and contrasts ratios to individual parts of the image.  By opposition, exposure functions of cameras are applied to entire image at once – so the two worlds don’t match very well.

 The future is in what is called “High Dynamic Range” in computer language, where all luminance levels can be captured, stored and displayed into (expensive) devices.

The lecture describes methods to photograph lighting design projects in such a way that results are as close as possible to the human eye perception. Workflows involving image manipulation programs are discussed and demonstrated. 

The attendee learned how to digitally capture the full range of luminance of any given scene (in our case, lighting design projects) with affordable hardware.  He also learned how to manipulate this data with affordable software to create a digital picture that is closer to his perception of the scene.

HDRI and Qualitative Lighting Simulation

HDR Imaging does not only improve our ability to photograph design projects.  It also allows us to improve our efficiency in lighting simulation workflows.  One can use a 3D rendering software to create one image per light source and combine them together in a compositing application.  The advantage of doing this is that the designer can interactively change the intensity of each layer in real time without re-rendering the model each time.

Typical techniques for achieving this workflow are demonstrated as well.

HDRI and Quantitative Lighting Analysis

HDR Imaging also gives us the possibility to perform advanced Daylighting studies of architectural and urban spaces.  We can use this technology to understand glare issues, yearly or monthly cumulative irradiances and more.

Application examples are shown in this lecture.