ABSTRACT
High dynamic range imaging High dynamic range imaging (HDR) is mostly about extending the dynamic range of the camera sensor to capture as wide a range of scenic tones as possible. Over the last few years digital camera sensors have improved significantly and some digital cameras are already capable of capturing a decent wide dynamic range. But in those situations where it is not possible to capture a sufficient range of tones with a single exposure the alternative is to blend an exposure-bracketed series of images together to create a single, high dynamic range image. Right now there are a lot of photographers interested in exploring what can be done using high dynamic range image editing. For example, using the Merge to HDR Pro feature in Photoshop you can combine two or more images that have been captured with a normal digital camera but shot at different exposures, and blend these together to produce a 32-bit floating point, high dynamic range image. You can then convert this 32-bit HDR file into a 16-bit per channel or 8-bit per channel low dynamic range version, which can then be further edited in Photoshop. In Figure 6.1, I show some examples of what high dynamic range processed images can look like. You are probably familiar with the typical ‘HDR look’ where there are obvious halos in the picture. While some photographers seem to like this kind of effect there has been a backlash against the illustrated feel of such images. However, good HDR editing does not always have to be about creating an artificial look. Basically, high dynamic range image editing requires a whole new approach to the way image editing programs like Photoshop process the high dynamic range image data. In fact, the Photoshop team had to rewrite a lot of the Photoshop code so that some of the regular Photoshop tools could be made to work in a 32-bit floating point image editing environment. Photoshop therefore does now offer a limited range of editing controls such as layers and painting in 32-bit mode. While the Merge to HDR Pro feature in Photoshop can be used do a good job, Camera Raw is also a very effective tool for creating and processing high dynamic range images.
