Clipping (photography)
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In digital photography and digital video, clipping is a result of capturing or
processing Processing is a free graphical library and integrated development environment (IDE) built for the electronic arts, new media art, and visual design communities with the purpose of teaching non-programmers the fundamentals of computer programming ...
an image where the intensity in a certain area falls outside the minimum and maximum intensity which can be represented. It is an instance of signal clipping in the image domain. The clipped area of the image will typically appear as a uniform area of the minimum or maximum brightness, losing any image detail. The amount by which values were clipped, and the extent of the clipped area, affect the degree to which the clipping is visually noticeable or undesirable in the resulting image. In a color image, clipping may occur in any of the image's color channels separately, which negatively affects colour reproduction. Clipping can occur at many different stages. It may occur in the
image sensor An image sensor or imager is a sensor that detects and conveys information used to make an image. It does so by converting the variable attenuation of light waves (as they pass through or reflect off objects) into signals, small bursts of curr ...
when initially capturing the image using a
digital camera A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile device ...
or scanner. It may occur due to internal
image processing An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimensiona ...
or
color space A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations of colorwhether such representation entails an analog or a digital represent ...
conversion in the camera or scanner. It may also result from later image processing using
image editing Image editing encompasses the processes of altering images, whether they are digital photographs, traditional photo-chemical photographs, or illustrations. Traditional analog image editing is known as photo retouching, using tools such a ...
software. Clipping that is due to internal image processing in a digital camera may often be partially or fully recovered if the raw sensor data is available, such as when saving to a
raw image format A camera raw image file contains unprocessed or minimally processed data from the image sensor of either a digital camera, a motion picture film scanner, or other image scanner. Raw files are named so because they are not yet processed and the ...
.


Clipping due to overexposure

Clipping can often occur in image highlights as a result of an incorrect exposure when initially photographing or scanning to a digital image. ''Increasing'' an exposure increases the amount of light collected or the sensitivity of the sensor, and increasing it too far will cause the lightest areas, such as the sky, or light sources, to clip. Bright areas due to overexposure are sometimes called blown-out highlights. In extreme cases, the clipped area may appear to have a noticeable border between the clipped and non-clipped area. The clipped area will typically be completely white, though in the case that only one color channel has clipped, it may represent itself as an area of distorted color, such as an area of sky that is greener or yellower than it should be. A similar effect also exists in
analog photography Analog photography, also known as film photography, is a catch-all term for photography that uses chemical processes to capture an image, typically on paper, film or a hard plate. These analog processes were the only methods available to phot ...
, though in that case it is not referred to as ''clipping'', and the blown-out area often curves off gently to its maximum brightness rather than being cut off abruptly as in clipping. This causes blown-out highlights to appear differently in analog and digital photography, with the smooth edges in analog photography regarded as more pleasant to some. In some cases, a small amount of clipping may be tolerable, especially when the clipped area is in the background of the image rather than part of the main subject, or is only a very small area such as a
specular highlight A specular highlight is the bright spot of light that appears on shiny objects when illuminated (for example, see image on right). Specular highlights are important in 3D computer graphics, as they provide a strong visual cue for the shape of a ...
(where a light, or the sun, is reflected in a shiny object).Understanding Digital Camera Histograms: Tones and Contrast
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Out-of-gamut clipping

Clipping in some color channels may occur when an image is rendered to a different
color space A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations of colorwhether such representation entails an analog or a digital represent ...
. When the image contains colors that fall outside the target color space, such colors are referred to as ''out-of-gamut''. This form of clipping may be avoided by performing the color space conversion using a different rendering intent. However, this can sometimes result in lower overall color saturation, leading to duller colors. The desire for bright, saturated colors may, in some cases, be more important than avoiding clipping in single channels due to out-of-gamut colors.


Digital video

Clipping may occur in
digital video Digital video is an electronic representation of moving visual images (video) in the form of encoded digital data. This is in contrast to analog video, which represents moving visual images in the form of analog signals. Digital video comprises ...
, just as in digital still photography. Just as with digital still photography, an intensity value that is outside the allowed range of values in any one channel causes clipping.


See also

*
Graduated neutral-density filter A graduated neutral-density filter, also known as a graduated ND filter, split neutral-density filter, or just a graduated filter, is an optical filter that has a variable light transmission. Typically half of the filter is of neutral density whic ...
*
High-dynamic-range imaging In photography and videography, multi-exposure HDR capture is a technique that creates extended or high dynamic range (HDR) images by taking and combining multiple exposures of the same subject matter at different exposure levels. Combining mu ...


References


What is white or black "clipping", and how does one avoid it?
(2011, September 23) {{DEFAULTSORT:Clipping (Photography) Science of photography