Shadow and highlight enhancement
Encyclopedia
Shadow and highlight enhancement refers to an image processing
technique to correct exposure
.
The use of this technique is becoming more and more popular, making its way onto magazine covers, digital media, and photos. It is, however, considered by some to be akin to other destructive Photoshop filters, such as the Watercolor filter, or the Mosaic filter.
technique, although this usually requires a tripod
.
of that top layer to "Soft Light". You can also use an inverted black and white copy of the image as a mask on a brightening layer, such as Curves or Levels.
Shadow enhancement can also be accomplished using adaptive image processing algorithms such as adaptive histogram equalization
or contrast limiting adaptive histogram equalization (CLAHE).
Image processing
In electrical engineering and computer science, image processing is any form of signal processing for which the input is an image, such as a photograph or video frame; the output of image processing may be either an image or, a set of characteristics or parameters related to the image...
technique to correct exposure
Exposure (photography)
In photography, exposure is the total amount of light allowed to fall on the photographic medium during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value and scene luminance over a specified area.In photographic jargon, an exposure...
.
The use of this technique is becoming more and more popular, making its way onto magazine covers, digital media, and photos. It is, however, considered by some to be akin to other destructive Photoshop filters, such as the Watercolor filter, or the Mosaic filter.
Recovering Shadows
A conservative application of the shadow/highlight tool can be very useful in recovering shadows, though it tends to leave a telltale halo around the boundary between highlight and shadow if used incorrectly. A way to avoid this is to use the bracketingBracketing
In photography, bracketing is the general technique of taking several shots of the same subject using different or the same camera settings. Bracketing is useful and often recommended in situations that make it difficult to obtain a satisfactory image with a single shot, especially when a small...
technique, although this usually requires a tripod
Tripod (photography)
In photography, a tripod is used to stabilize and elevate a camera, or to support flashes or other photographic equipment. All photographic tripods have three legs and a mounting head to couple with a camera...
.
Recovering Highlights
Recovering highlights with this tool, however, has mixed results, especially when using it on images with skin in them, and often makes people look like they have been "sprayed with fake tan".Manual Ways to Brighten Shadows
One way to brighten shadows in image editing software such as Gimp or Adobe Photoshop is to duplicate the background layer, invert the copy and set the blend modesBlend modes
Blend modes in digital image editing are used to determine how two Layers are blended into each other. The default blend mode in most applications is simply to hide the lower layer with whatever is present in the top layer...
of that top layer to "Soft Light". You can also use an inverted black and white copy of the image as a mask on a brightening layer, such as Curves or Levels.
Automatic Shadow Recovery Methods
There exist a number of automatic computer image processing-based shadow recovery and dynamic range compression methods that yield a similar effect. Some of these methods include the retinex method and homomorphic range compression. The retinex method is based on work from 1963 by Edwin Land, the founder of Polaroid.Shadow enhancement can also be accomplished using adaptive image processing algorithms such as adaptive histogram equalization
Adaptive histogram equalization
Adaptive histogram equalization is a computer image processing technique used to improve contrast in images. It differs from ordinary histogram equalization in the respect that the adaptive method computes several histograms, each corresponding to a distinct section of the image, and uses them to...
or contrast limiting adaptive histogram equalization (CLAHE).
See also
- Tone mappingTone mappingTone mapping is a technique used in image processing and computer graphics to map one set of colors to another in order to approximate the appearance of high dynamic range images in a medium that has a more limited dynamic range...
- HDR PhotoStudioHDR PhotoStudioHDR PhotoStudio is an advanced HDR digital imaging software application developed by Unified Color for Microsoft Windows XP/Vista/7 and Apple's Mac OS X...
— an HDR image editing tool that implements an advanced Shadow/highlight algorithm with halo reduction technique.