High Dynamic Range (HDR) Photography. I myself do not completely understand the full process of HDR. It is a post-processing method of taking either one image or a series of images, combining them, and adjusting the contrast ratios to do things that are virtually impossible with a single aperture and shutter speed. Basically it allows you to display the full range of light that you see with the human eye. This tends to make the photograph appear on paper as you remembered it in you’re mind. For me though, this is part of what makes it such a fun and rewarding thing to do. Besides the fact that I love photography to begin with, it seems there is always something new to learn.
In image processing, computer graphics, and photography, high dynamic range imaging (HDR) is a set of techniques that allows a greater dynamic range between the lightest and darkest areas of an image than current standard digital imaging techniques or photographic methods. This wide dynamic range allows HDR images to represent more accurately the range of intensity levels found in real scenes, ranging from direct sunlight to faint starlight, and is often captured by way of a plurality of differently exposed pictures of the same subject matter.
HDR is a range of techniques to achieve more contrast in pictures. Non-HDR cameras take pictures at a single exposure level. This results in the loss of detail in bright or dark areas of a picture, depending on whether the camera had a low or high exposure setting. HDR compensates for this loss of detail by taking multiple pictures at different exposure levels and intelligently stitching them together so that we get a picture that is representative in both dark and bright areas.
High-dynamic-range photographs are achieved by capturing multiple photographs, using exposure bracketing, and then merging them into an HDR image. Digital photographs are often encoded in a camera’s raw image format, because 8 bit JPEG encoding doesn’t offer enough values to allow fine transitions (and also introduces undesirable effects due to the lossy compression).
Any camera that allows manual over- or under-exposure of a photo can be used to create HDR images.
Some cameras have an auto exposure bracketing (AEB) feature with a far greater dynamic range than others, from the 3 EV of the Canon EOS 40D, to the 18 EV of the Canon EOS-1D Mark II. As the popularity of this imaging technique grows, several camera manufactures are now offering built in HDR features.
Photoshop CS2 introduced the Merge to HDR function.
Tone mapping in digital photography
Tone mapping is a post-processing technique, using Photomatix Pro photographic software
Brightening shadows and altering contrast applied globally to digital images as part of a professional or serious amateur workflow is also a form of tone mapping.
Not all tone mapped images are visually distinctive. Reducing dynamic range with tone mapping is often useful in bright sunlit scenes, where the difference in intensity between direct illumination and shadow is great. In these cases the global contrast of the scene is reduced, but the local contrast maintained, while the image as a whole continues to look natural. Use of tone mapping in this context may not be apparent from the final image: