The American Society of Cinematographers Color Decision List (ASC CDL) is a format for the exchange of basic primary color grading information between equipment and software from different manufacturers. The format defines the math for three functions: Slope, Offset and Power. Each function uses a number for the red, green, and blue color channels for a total of nine numbers comprising a single color decision. A tenth number, Saturation, specified in the Version 1.2 release, applies to the R, G, and B color channels in combination.
The ASC CDL was developed by the ASC Technology Committee, a combined group of cinematographers, post-production engineers, and other motion picture industry professionals.
Although the basic controls of most color correction systems are similar, they differ somewhat in specific implementation and detail. The ASC CDL is a common standard that color correctors can translate their proprietary settings to and from. The ASC CDL functions are mathematically orthogonal primitives that can be used to represent vendor-specific corrections. ASC CDL correction functions also in some cases can appear in the user interface and be used directly.
The ASC CDL allows color corrections made with one device at one location to be applied or modified by other devices elsewhere. For example, a cinematographer filming on location can create a color correction with a small portable device, sending the ASC CDL color correction to a colorist in post-production to use as a starting point for final color correction. To communicate "looks" usefully in this fashion, calibrations, viewing environments, devices, and any output transforms (e.g. film look) must be managed very carefully; in general, they should be identical at origination and subsequent viewing.
The ASC has defined an XML schema for exchanging ASC CDL data, along with other metadata about what image(s) the color corrections were applied to, the type of input signal used, and the viewing device and environment. They have also standardized methods for using ASC CDL data within the following file formats:
The formula for ASC CDL color correction is:
where
The formula is applied to the three color values for each pixel using the corresponding slope, offset, and power numbers for each color channel.
Instructions for getting the current release of ASC CDL implementor-oriented documentation can be retrieved by sending an e-mail to asc-cdl at theasc dot com.
In computer graphics, alpha compositing or alpha blending is the process of combining one image with a background to create the appearance of partial or full transparency. It is often useful to render picture elements (pixels) in separate passes or layers and then combine the resulting 2D images into a single, final image called the composite. Compositing is used extensively in film when combining computer-rendered image elements with live footage. Alpha blending is also used in 2D computer graphics to put rasterized foreground elements over a background.
JPEG or JPG is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable trade-off between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality. Since its introduction in 1992, JPEG has been the most widely used image compression standard in the world, and the most widely used digital image format, with several billion JPEG images produced every day as of 2015.
The RGB color model is an additive color model in which the red, green, and blue primary colors of light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three additive primary colors, red, green, and blue.
Gamma correction or gamma is a nonlinear operation used to encode and decode luminance or tristimulus values in video or still image systems. Gamma correction is, in the simplest cases, defined by the following power-law expression:
YUV is a color encoding system typically used as part of a color image pipeline. It encodes a color image or video taking human perception into account, allowing reduced bandwidth for chrominance components, thereby typically enabling transmission errors or compression artifacts to be more efficiently masked by the human perception than using a "direct" RGB-representation. Other color encodings have similar properties, and the main reason to implement or investigate properties of Y′UV would be for interfacing with analog or digital television or photographic equipment that conforms to certain Y′UV standards.
Digital image processing is the use of a digital computer to process digital images through an algorithm. As a subcategory or field of digital signal processing, digital image processing has many advantages over analog image processing. It allows a much wider range of algorithms to be applied to the input data and can avoid problems such as the build-up of noise and distortion during processing. Since images are defined over two dimensions digital image processing may be modeled in the form of multidimensional systems. The generation and development of digital image processing are mainly affected by three factors: first, the development of computers; second, the development of mathematics ; third, the demand for a wide range of applications in environment, agriculture, military, industry and medical science has increased.
ITU-R Recommendation BT.601, more commonly known by the abbreviations Rec. 601 or BT.601 is a standard originally issued in 1982 by the CCIR for encoding interlaced analog video signals in digital video form. It includes methods of encoding 525-line 60 Hz and 625-line 50 Hz signals, both with an active region covering 720 luminance samples and 360 chrominance samples per line. The color encoding system is known as YCbCr 4:2:2.
The BMP file format, also known as bitmap image file, device independent bitmap (DIB) file format and bitmap, is a raster graphics image file format used to store bitmap digital images, independently of the display device, especially on Microsoft Windows and OS/2 operating systems.
In digital photography, computer-generated imagery, and colorimetry, a grayscale image is one in which the value of each pixel is a single sample representing only an amount of light; that is, it carries only intensity information. Grayscale images, a kind of black-and-white or gray monochrome, are composed exclusively of shades of gray. The contrast ranges from black at the weakest intensity to white at the strongest.
Pixels per inch (ppi) and pixels per centimetre are measurements of the pixel density of an electronic image device, such as a computer monitor or television display, or image digitizing device such as a camera or image scanner. Horizontal and vertical density are usually the same, as most devices have square pixels, but differ on devices that have non-square pixels. Note that pixel density is not the same as resolution, where the former describes the amount of detail on a physical surface or device, while the latter resolution describes the amount of pixel information regardless of its scale. Considered in another way, a pixel has no inherent size or unit, but when it is printed, displayed, or scanned, then the pixel has both a physical size (dimension) and a pixel density (ppi).
sRGB is a standard RGB color space that HP and Microsoft created cooperatively in 1996 to use on monitors, printers, and the Web. It was subsequently standardized by the IEC as IEC 61966-2-1:1999. Its predecessor NIF RGB was used in FlashPix and was almost the same. It is often the "default" color space for images that contain no color space information, especially if the images' pixels are stored in 8-bit integers per color channel.
In photography and image processing, color balance is the global adjustment of the intensities of the colors. An important goal of this adjustment is to render specific colors – particularly neutral colors – correctly. Hence, the general method is sometimes called gray balance, neutral balance, or white balance. Color balance changes the overall mixture of colors in an image and is used for color correction. Generalized versions of color balance are used to correct colors other than neutrals or to deliberately change them for effect.
Histogram equalization is a method in image processing of contrast adjustment using the image's histogram.
Silicon Graphics Image (SGI) or the RGB file format is the native raster graphics file format for Silicon Graphics workstations. The format was invented by Paul Haeberli. It can be run-length encoded (RLE). FFmpeg and ImageMagick, among others, support this format.
A co-occurrence matrix or co-occurrence distribution is a matrix that is defined over an image to be the distribution of co-occurring pixel values at a given offset. It is used as an approach to texture analysis with various applications especially in medical image analysis.
In digital photography, the image sensor format is the shape and size of the image sensor.
In computing, a bitmap is a mapping from some domain to bits. It is also called a bit array or bitmap index.
Rec. 709, also known as Rec.709, BT.709, and ITU 709, is a standard developed by ITU-R for image encoding and signal characteristics of high-definition television.
The American Society of Cinematographers Technology Committee is a group of cinematographers and a broad collection of A-list motion picture industry participants working on how to make high quality motion pictures using the new technologies and techniques presented by the massive changes taking place in pre-production, cameras, production, post-production, theatrical delivery and exhibition, and non-theatrical (home) delivery and exhibition. The ASC Technology Committee has been one of the industry leaders in these areas. Significant work produced includes the ASC-DCI Standard Evaluation Material (StEM), the ASC-PGA Camera Assessment Series (CAS), and the ASC Color Decision List.
ITU-R Recommendation BT.2020, more commonly known by the abbreviations Rec. 2020 or BT.2020, defines various aspects of ultra-high-definition television (UHDTV) with standard dynamic range (SDR) and wide color gamut (WCG), including picture resolutions, frame rates with progressive scan, bit depths, color primaries, RGB and luma-chroma color representations, chroma subsamplings, and an opto-electronic transfer function. The first version of Rec. 2020 was posted on the International Telecommunication Union (ITU) website on August 23, 2012, and two further editions have been published since then. It is expanded in several ways by Rec. 2100.
