Before getting into the details, it would help to have some terms of reference. In brief, dynamic range (DR) is the range of luminance values from the darkest to the brightest. The original, real-world scene has a certain inherent DR which may be quite large – a ratio of 100,000:1 or more as DR is measured. Your eyes can perceive a subset of the scene’s DR (about 10,000:1), while your camera can record a smaller subset than your eyes can see – perhaps 400:1 for a DSLR. The DR of a monitor or a printed photograph is smaller yet. High dynamic range (HDR) in photography means representing the full range of tonality present in the scene with high perceptual faithfulness. Most HDR techniques currently use software to combine several different exposures of a scene into a single file that maps the full range of luminance
at every pixel. This HDR image is then processed in various ways depending
on the ultimate usage. For most of us this means tone mapping the HDR image into a 16-bit or 8-bit digital file such as a JPEG or TIFF image. If this is enough definition for you and you want to get into the part that shows how to get things done, feel free to skip ahead to the next section on shooting technique. The rest of this section provides the details of what HDR is for those who prefer to know “what” before getting into the “how”.
Key points covered in the rest of this section:
- Definition of HDR
- HDR vs. 8-bit or 16-bit file formats
- Capturing HDR images
- What is HDR good for?