Introduction

What you can expect from this book

This book will reveal the many secrets behind high dynamic range imaging (HDRI).

You have heard this term before, and maybe you have even worked with a high dynamic range image before. The simple fact that you are holding this book in your hand shows that HDRI is not all that new to you. But still, you want to know more. You want to know the full story, and I know exactly why.

Currently, there is a lot of talk about high dynamic range imaging in the online photography communities. The topic emerged from discussions about taking better pictures in difficult lighting conditions, and it turned out that HDRI is just the right tool to address this challenge. But HDRI is much more.

To cut a long story short: High dynamic range imaging is a method to digitally capture, store, and edit the full luminosity range of a scene. We are talking about all the visible light here, from direct sunlight down to the finest shadow details. Having all that available in one image opens the door for immense opportunities in post processing. HDRI is a quantum leap; it is just as revolutionary as the leap from black-and-white to color imaging. Or, for a more suitable analogy, HDRI is to a regular image what Dolby surround sound is to mono tape. If you are serious about photography, you will find that high dynamic range imaging is the final step that puts digital ahead of analog. The old problem of over- and underexposure-in analog photography never fully solved-is elegantly bypassed. HDRI extends the digital development process beyond anything that was ever possible in an analog darkroom. Correct exposure is not an on-site decision anymore; it becomes a flexible parameter that can be dealt with in entirely new ways. An HDR image is like a digital negative on steroids, more like a true representation of the scene than a mere photographic image. You can even take measurements of true world luminance values in an HDR image. For example, you can point at a wall and determine that it reflects sunlight equal to 40,000 cd/m2. Even better, if the HDR image is panoramic, you can apply all the captured light to 3D objects.

High dynamic range imaging is an emerging field, but it is not all that new anymore. It has become a mature technology. It has just been poorly documented. Until now.

Five years ago, HDRI was a huge buzzword in the world of computer graphics (CG). It was considered the holy grail of true photorealism, the magic "make it cool" button that everyone was looking for. Fully digitally generated images were popping up, and even professionals could not tell if they were photographs or not. Hollywood studios were the first to adapt and implement that technology because their daily business is to fool the audience and sell them artificial dream worlds as the real thing. By now, HDRI has become a standard tool, even for the 3D hobbyist at home. Everyone and his dogs know how to use HDR images to make a rendering look photo-realistic. When they watch the Making Of feature for the latest blockbuster movie and the art director talks about lighting all the computer graphics with HDRI, everyone is nodding his head, mumbling, "Ah, sure... so that's why it looks so good." But what is really behind this technology? How can an HDR image be used as a light source? It's just an image, isn't it? How does it work? And can you make an HDR image yourself? Exactly how would that be done?

Many questions are still open, even for the 3D folks who have been using HDRI for years. Because using something is different from understanding something. Only if you really understand the nature of HDRI will you be able to develop your own way of working with it. That's why this book digs deeper than a footnote or a single chapter in a software specific tutorial book. Reading it from cover to cover will build a comprehensive knowledge base that will enable you to become really creative with HDRI. Regardless of whether you are a photographer, a 3D artist, a compositor, or a cinematographer, this book is certain to enlighten you.