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HDR-Photography
Ever heard the word HDR or HDRI, but you have no clue what it actually stands for? Here’s a non-techy article about HDR-Photography. If you want to, you can listen to Chris's Show on HDR-Photography concurrent.
What is HDR?
HDR(I) stands for High Dynamic Range (+ Increase) and is a way to store images using a much higher amount of information than traditional formats like JPEG allows.
Dynamic Range is the range of a camera (or any other optical device - Just like our eyes) between the darkest and the brightest area the camera is able to capture. Unfortunately, there are tight limits for the range the camera can handle - Our human eye is much better when it comes to dynamic range. I’m sure you all have experienced this effect already on your pictures.
Imagine a bright sunny scene at midday. The bright spots casted by the sun and the darker shadows are often too much for the digital camera. You now can only get detail on the bright spots while losing detail in the darker areas of the picture, or more details on the darker spot while over-exposing the brighter ones.
In order to fix that problem, that’s the situation where HDR comes in. While there’s no camera available on the market to reproduce the possibilities of what our eyes can see, you can fake that using several pictures of the same scene and combining them to one image. But why multiple images? Easy, some of the pictures will then have details in the brighter areas, others in the darker ones. Combining them to a single HDR-Photo. This process is called bracketing.
Of Course you need a tripod or a beanbag in order to seamlessly combine all the images. The last problem is the output medium. As monitors and paper are limited in terms of dynamic range. So even if you have created a high-quality HDR-picture on the computer, you will have to re-map the picture into a lower dynamic range that the monitor can handle. This process is called Tone-Mapping.
You might ask how you can achieve all those steps. And as many other things, these steps are done with the help of software. There are several images that will take over the bracketing and Tone-Mapping for you. Photoshop CS2© has HDR-Image support built in already. A few others are Photomatix and EasyHDR.
Besides for Photography, HDR is also used for 3d-Applications and games in order to display a more natural and realistic lighting of the scene.
Resume
For the average photographer, HDR is only of limited use. The current digital cameras can not display a bigger dynamic range and so images needs to be put together manually. We won’t see HDR’s potential until new devices come out that can actually display greater dynamic range in one single exposure.
