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.
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:
Texture mapping is a method for mapping a texture on a computer-generated graphic. "Texture" in this context can be high frequency detail, surface texture, or color.
In computer graphics, a line drawing algorithm is an algorithm for approximating a line segment on discrete graphical media, such as pixel-based displays and printers. On such media, line drawing requires an approximation. Basic algorithms rasterize lines in one color. A better representation with multiple color gradations requires an advanced process, spatial anti-aliasing.
Chroma subsampling is the practice of encoding images by implementing less resolution for chroma information than for luma information, taking advantage of the human visual system's lower acuity for color differences than for luminance.
The BMP file format or 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.
YCbCr, Y′CbCr, or Y Pb/Cb Pr/Cr, also written as YCBCR or Y′CBCR, is a family of color spaces used as a part of the color image pipeline in video and digital photography systems. Y′ is the luma component and CB and CR are the blue-difference and red-difference chroma components. Y′ is distinguished from Y, which is luminance, meaning that light intensity is nonlinearly encoded based on gamma corrected RGB primaries.
sRGB is a standard RGB color space that HP and Microsoft created cooperatively in 1996 to use on monitors, printers, and the World Wide Web. It was subsequently standardized by the International Electrotechnical Commission (IEC) as IEC 61966-2-1:1999. sRGB is the current defined standard colorspace for the web, and it is usually the assumed colorspace for images that are neither tagged for a colorspace nor have an embedded color profile.
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 like white or grey – 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. White balance is one of the most common kinds of balancing, and is when colors are adjusted to make a white object appear white and not a shade of any other colour.
Proportional control, in engineering and process control, is a type of linear feedback control system in which a correction is applied to the controlled variable, and the size of the correction is proportional to the difference between the desired value and the measured value. Two classic mechanical examples are the toilet bowl float proportioning valve and the fly-ball governor.
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 graphic is an image formed from rows of different colored pixels. A GIF is an example of a graphics image file that uses a bitmap.
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.
Ordered dithering is any image dithering algorithm which uses a pre-set threshold map tiled across an image. It is commonly used to display a continuous image on a display of smaller color depth. For example, Microsoft Windows uses it in 16-color graphics modes. The algorithm is characterized by noticeable crosshatch patterns in the result.
Blend modes in digital image editing and computer graphics are used to determine how two layers are blended with each other. The default blend mode in most applications is simply to obscure the lower layer by covering it with whatever is present in the top layer ; because each pixel has numerical values, there also are many other ways to blend two layers.
The American Society of Cinematographers Technology Committee (ASC 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 (ASC CDL).
The operational amplifier integrator is an electronic integration circuit. Based on the operational amplifier (op-amp), it performs the mathematical operation of integration with respect to time; that is, its output voltage is proportional to the input voltage integrated over time.
In computer vision, a saliency map is an image that highlights either the region on which people's eyes focus first or the most relevant regions for machine learning models. The goal of a saliency map is to reflect the degree of importance of a pixel to the human visual system or an otherwise opaque ML model.
