What is HDR?
HDR stands for High Dynamic Range. Sometimes they are referred to as HDRI or High Dynamic Range Images. It is a method of photography developed by the research of Paul Debevec at USC that exposes both dark and light values of an image.
For example, if you take an ordinary photograph of an interior room facing a window, the room will be properly exposed but everything outside the window will be “blown out” or overexposed with white. However, if you take the same picture with the focus being what exists outside of the window, then the interior will be dark, or underexposed.
In contrast to ordinary photographs, the human eye naturally exposes both the light and dark values of a room with a window view. Presently, cameras cannot intelligently distinguish these differences. HDR was developed to help circumvent these issues.
How Does HDR Work?
HDR images are processed by taking multiple exposures of the same camera shot at varying levels – from extremely dark to middle, and to very bright. They are then combined together using processing software. You are then able to more accurately control both the highlights and dark values (exposure) to create a more realistic photograph that circumvents the pitfalls of traditional photography. The software also guesses or “extrapolates” information beyond those initial photographs (also known as Floating Point data) – allowing you to accurately guess even darker and brighter image values that go beyond the images which you had taken.
Why Are You Involved with HDR?
I started off in HDR because it has its basis in computer graphics. Greg Ward is considered the father of a 3d lighting technique known as Image Based Lighting or IBL. IBL essentially uses an image or a photograph to light a 3d model. HDR can be used as a more “accurate” or “real world” IBL method of lighting a 3d scene and that is where it got its start.
I was an early adopter to this method when I first taught myself 3d graphics. Most of it was coincidental – I had set out to try to achieve a more realistic look with my models when I came across Debevec’s research that I started to read.
Over time, HDR was slowly becoming a more popular field as more people realized its potential. With the eventual release of basic HDR support in the Adobe Photoshop Creative Suite, the technique has become more popular with ordinary photographers.
For me, it has become a fun hobby of sorts with a variety of technical challenges, but also a hobby that has practical uses for 3d applications. It is also something that most people are unfamiliar with, and it produces some fairly unique results which makes you “stand out” from the crowd.
Why Do Your HDRs Not Resemble Other HDRs I’ve Seen on the Web?
You mean, “why doesn’t your images have a radioactive look to them?” It’s because I try to mimic real-world conditions as seen through the human eye for 3D applications. That’s where HDR has its foundation. Many photographers on the other hand, have discovered that they can take these HDRs and create some highly unusual (and often unrealistic) results with adjusting the sliders of applications, or what is often termed as “tonemapping.”
What’s Better – Realistic or Unrealistic HDRs?
It’s a matter of preference and a source of debate amongst proponents. I’ve seen some “overdone” HDRs, but also some HDRs that are absolutely astounding. For the sake of 3D applications, most of the time you want to achieve more natural results to light your scenes properly. I suppose that if there was a “true” answer, it would be to mimic reality. Ultimately from an artistic standpoint, it comes down to a matter of taste.
Why do You Take “Warped” or “Elongated” HDRs?
These photos involve stitching multiple photographs and exposures together to create a 360-degree panoramic format which are used to envelop a 3-d scene in the environment and lighting of a HDR. It is the most commonly used format for 3D currently. The technique, sans the HDR aspect also happens to be used to create “3D Virtual Tours” on the Internet for purposes such as marketing properties and Real Estate. However, I can (and do) take ordinary images as well.
Additional General HDR Information and Resources:
Additional information can be found throughout the Internet. A simple Google search for “HDR” or” HDRI” will turn up a lot of results – some of which are accurate and many which are not.
For starters, I would recommend checking out the following links:
http://en.wikipedia.org/wiki/High_dynamic_range_imaging – General HDR information.
http://www.hdrlabs.com – A more comprehensive resource and forum started by Christian Bloch.
The HDRI Handbook – One of the first HDR books written by Christian Bloch.
