What are the differences between Exposure Fusion and HDR/Tone mapping?

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What are the differences between Exposure Fusion and HDR/Tonemapping?
Both processes start from the same source files: differently exposed Low Dynamic Range (LDR) images. And both attempt to produce as final result an LDR image that shows tonal details of the entire dynamic range captured by the different exposures.
The differences are in the process itself. Exposure Fusion consists in combining the differently exposed images in such a way that highlight details are taken from the underexposed photos and shadows details from the overexposed ones. Since the bit-depth does not change throughout this process, the basis of Exposure Fusion algorithms is a type of weighted average of the source images.
One of the advantage or Exposure Fusion is that it is easy to understand and you can see what you are doing. Also, it is rather familiar to photographers who are used to doing this process manually in image editing applications. Another advantage of Exposure Fusion is that it reduces noise.
HDR Photography How To:HDR Tone Mapping is composed of two steps. The first step creates an HDR image from differently exposed photos. This HDR image can not be displayed correctly on a Low Dynamic Range monitor, which is why a second step called Tone Mapping is necessary. Tone Mapping consists in scaling each pixel of the HDR image, so that details in highlights and shadows show correctly on monitors and prints (those details are available in the HDR image but not directly visible in both highlights and shadows because of the low dynamic range of the display).
Tone Mapping algorithms vary from a simple gamma curve (which is often what cameras are doing when converting 12-bit RAW data to 8-bit JPEGs) to more complex operators commonly divided into two categories:
· Global operators: mapping depends on the pixels’ intensity and global image characteristics, but not on spatial location
· Local operators: mapping takes into account the pixels’ surroundings (in addition to intensity and image characteristics).
The main advantage of global operators is fast processing. Local operators require longer processing times but they are better at producing a “good-looking” photograph (the human eye adapts to contrast locally). In Photomatix Pro, the Tone Mapping method “Details Enhancer” belongs to the category of local operators and the method “Tone Compressor” to the category of global operators.
The pros and cons of Exposure Fusion vs Tone Mapping in Photomatix Pro are detailed under the section below.

2 comments

  1. Same question. Where is the section bellow at which are you referring to?

    “The pros and cons of Exposure Fusion vs Tone Mapping in Photomatix Pro are detailed under the section below.”

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