Highy Dynamic Range Imaging (HDRI or HDR) is a set of techniques that allow a greater dynamic range of between the lightest and darkest areas of an image than current standard digital imaging techniques or photographic methods. In photography, this is usually achieved by shooting multiple photos with different exposure settings of the same scene and later combining them into a single HDR image using specialized software.
For a long time I wan’t interested in HDR at all, mainly because most of the HDR images I saw were absolutely awful. But if you take a closer look you’ll also find that some people made amazing HDR stuff. So why not give it a try?
(I later found out that most of the extremely ugly HDR images result from the Enhancer – Grunge preset in the Photomatrix Pro software. Many people seem to think that bad photos become interesting or good ones if you turn them into HDR. Or that you get the best results if you push all sliders in the software [Strength, Color Saturation, Luminosity and Detail Contrast] to the very right) I do not blame this on the software of course, you can do some good stuff with little effort in Photomatrix.
What is HDR?
The dynamic range of the human eye is much larger than the one of the sensors of current DSLRs or other technical devices (see here). Our eyes “expose” for the part of the “image” we are currently interested in: they adapt to varying brightness levels when you look at different areas of a scene, e.g. by the pupillary light reflex.
A camera on the other hand captures the whole scene with the same exposure. This means that if you are trying to capture a scene which involves a hight tonal range with a single shot, you can only preserve details in the highlights or the shadows. Taking several photos and combining them later allows you to overcome this problem (or at least make it less severe). But producing the image is only half of the problem. The other part is how to display a HDR image on a device that also has a very limited dynamic range (e.g., an LCD or CRT monitor). This problem is addressed by a process known as tone mapping, which is also done in a HDR software package. Essentially, tone mapping addresses the problem of strong contrast reduction from the scene values (radiance) to the displayable range while preserving the image details and color appearance important to appreciate the original scene content.
You can select a tone mapping method and control the tone mapping process in the software and depending on the settings you choose, the results can vary dramatically. Even if you are going for a very realistic look, people can usually tell that an image is a HDR.
An example for a HDR software is the great and free Luminance HDR (formerly known under the intuitive name qtpfsgui – no, that’s not a typo). A commercial alternative is Photomatrix Pro by HDRSoft. There sure as hell are a lot more but I didn’t try them and thus won’t talk about them, just use your favorite search engine if you care. 😉
Apart from the software, all you need is a camera and a tripod.
Shooting HDR with the Nikon D7000
If you want to create HDR images, you’ll have to shoot several shots with different exposure settings of the same scene (bracketing) and later combine them into a single image. The next post in this series is gonna explain how to do this with a Nikon D7000 (and similar cameras).