DOCSLIB.ORG

PROCESSES in BIOLOGICAL VISION: Including

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
PROCESSES in BIOLOGICAL VISION: Including PROCESSES IN BIOLOGICAL VISION: including, ELECTROCHEMISTRY OF THE NEURON This material is excerpted from the full β-version of the text. The final printed version will be more concise due to further editing and economical constraints. A Table of Contents and an index are located at the end of this paper. James T. Fulton Vision Concepts [email protected] April 30, 2017 Copyright 2001 James T. Fulton Performance Descriptors 17- 1 17 Performance descriptors of Vision1 Because of the amount of color artwork in this chapter, it has been necessary to divide it into three parts for distribution over the INTERNET. PART 1A: INTRO, LUMINANCE & NEW CHROMATICITY DIAGRAM PART 1B: EXTENSIONS TO THE NEW CHROMATICITY DIAGRAM PART 2: TEMPORAL AND SPATIAL DESCRIPTORS OF VISION PART 1B: NEW CHROMATICITY DIAGRAM DEFINITIONS AND COMPARISONS TO OTHER COLOR SPACES The press of work on other parts of the manuscript may delay the final cleanup of this PART but it is too valuable to delay its release for comment. Any comments are welcome at [email protected]. 17.3.4 New definitions based on the New Chromaticity Diagram 17.3.4.1 The general concepts of narrow and broadband colors [new intro From a spectral perspective, the color of an object involves the evaluation of the centroid of two samples of its radiance function. How this is accomplished by the visual system will be developed below. Much confusion has surrounded the fact that the radiance of an object frequently involves the product of the reflectance function of an object multiplied by the irradiance function of the light applied to the object. The definition of the color of an object depends on the situation. Using a strictly psychophysical definition related to the perceived color reported by an animal is of little use to the image reproduction specialist. The specialists in photography, television and other image reproduction fields require definitions independent of the complex system represented by the animal visual system. However, these specialists would always like to know the interrelationship between the color observed by their system and the animal system. To provide a precise yet comprehensive definition of the phenomena of color requires careful specification of the conditions involved. The following two sections should be considered as a set. While the discussion in the first section appears comprehensive, it actually contains a subtle and very significant oversight. This oversight, which is found within the description of definition #5 is most easily addressed as a separate amendment to the first discussion. It is addressed in the second section. The subject of asymmetric illumination of the two eyes of an observer also introduces another condition requiring a separate definition of color. The color reported by a subject under this condition clearly involves cognition in the cortex. Cognitive color will be used to describe this situation. 17.3.4.1.1 First Order definitions Amazing as it may seem, the visual science community has suffered from the lack of a widely accepted and precise definition of the phenomena of color. This does not mean that there are not definitions of the phenomena of color. It focuses on the fact that there are a proliferation of definitions that are inconsistent, both conceptually and mathematically imprecise, and not widely accepted. The problem is partly due to the inadequacy of language (at 1Released April 30, 2017 2 Processes in Biological Vision least the English language) to provide the needed differentiation between various aspects of color as found in the signaling chain of both animal vision and man-made image recording. This problem is highlighted at the current time by the explosion in interest concerning the poorly defined phenomena of color constancy as noted in human vision. To simplify the following discussion, only objects that are not self-radiating will be discussed . Although Roget’s Thesaurus provides about twenty multiple word synonyms for various aspects of color, it gives virtually no single word synonym for the word color. The Encarta Encyclopedia hedges its bet with the description of light as the “physical phenomenon of light or visual perception associated with the various wavelengths in the visible portion of the electromagnetic spectrum.” [italics added] In the context of this work, color can be defined with conceptual and mathematical precision by using modifying adjectives (sometimes multiple adjectives). This is most easily done by defining the phenomena of color specifically at each applicable stage in the visual process. Wyszecki & Stiles used this approach to define about ten different types of color. Unfortunately, their definitions are all conceptual and based on semantics rather than physics/mathematics. This work will define color in terms of several primary situations; 1. the intrinsic color of an object independent of how it is observed, 2. the sampled color of an object as observed by an instrument that samples the light emanating from an object, 3. the sampled trichromatic color of an object as observed by an instrument that samples the light emanating from an object using spectrally selective radiometers analogous to those of the long wavelength trichromatic animal eye, 4. the applied color of an object in terms of its spectral content at the Petzval surface of an optical system, 5. the adapted color of an object as found at the pedicels of the photoreceptor cells of the animal eye, 6. the encoded color of an object as represented by the signals within the chrominance channels of the visual system and 7. the perceived color of an object reported by an animal. Note that none of these definitions involve the employment of comparative or null techniques in object space. Discussions of the color of an object frequently become entangled with the spectral aspects of an illuminating source and the intrinsic reflectance of the object. This can be avoided if the illuminating source is defined so as to make its impact on the color of the object negligible. If the illuminating source is chosen such that it applies spectrally, spatially and temporally uniform irradiation to the object from a spherical source centered on the object, any variation in the characteristics of the radiation emanating from the object in a given direction, and possibly within a given cone angle centered on that direction, will be due to the intrinsic properties of the object. A caveat is that the spectral uniformity is measured with respect to radiant flux intensity of the source and not radiant energy intensity. This condition can be applied over any wavelength (frequency) interval without changing the experiment. However, in the case of vision, the wavelength interval need only extend over the wavelength interval to which the sensory system of the animal is responsive. For tetrachromats (including many small terrestrial mammals), this interval is not less than 300 to 700 nm. A somewhat narrower range can be used for trichromats; 300 to 600 nm for short wavelength trichromats and 400 to 700 nm for long wavelength trichromats (such as human and other large terrestrial mammals). This condition also effectively eliminates any observable form of specular reflection from the object. If the specular characteristics of the radiation from the object are required, a different illumination source will be required. As noted repeatedly in this work, the use of energy per unit wavelength as a parameter in visual research leads to endless difficulties. The visual system is a photoelectric class of device that is sensitive to the number of photons absorbed per interval. It is not properly represented as being sensitive to the amount of energy absorbed per interval, as would be the case in a thermoelectric class of device. Use of a spectral power density (SPD) to describe a radiation source is not appropriate for vision research. The use of a spectral flux density (SFD) distribution would be more useful. 1. Under the above conditions, the intrinsic color of a uniformly colored object is given by the spectral distribution of the light emanating from the object in any direction within the specified spectral limits. This intrinsic color is invariant with the intensity of the specified illumination source. 2. Since it is difficult to convey the intrinsic color of an object semantically when it is only represented by a continuous spectral distribution, an additional step is common. It is common to sample the continuous spectral Performance Descriptors 17- 3 distribution, using multiple narrow spectral band radiometric flux (not energy) detectors and report the relative intensity readings of these detectors. The individual radiometric flux detectors are calibrated to insure equal sensitivity to a uniform radiometric flux source. When implemented in a man-made instrument, this procedure is analogous to the initial photodetection stage of the animal eye. The result is defined here as the sampled color of the object. In the above procedure, it is necessary to describe both the relative readings of the individual detectors and the spectral characteristics of each detector. 3. A single valued description of the sampled color is not obtained using the above method. However, if the spectral characteristics of the individual detector channels are standardized, a simpler description of the sampled color of the object is possible. Traditionally, such a standardization has been based on the so-called tristimulus spectrums recommended by the CIE Unfortunately, these spectrums are artificial and do not conform to the spectrums of the photodetectors in the animal (including human) eye. As a result, such instruments have given confusing results. By using the actual spectrums of the chromophores of vision presented here in the instrument, results can be obtained which are more closely correlatable to the perceived color reported by an observer under conditions of constant illumination. If three radiometric flux detectors are used to emulate the spectral characteristics of a long wavelength trichromat, the instrument will provide three values that concisely describe the sampled trichromatic color of the object.
Load more

Recommended publications
  • Understanding Color and Gamut Poster
    Understanding Colors and Gamut www.tektronix.com/video Contact Tektronix: ASEAN / Australasia (65) 6356 3900 Austria* 00800 2255 4835 Understanding High Balkans, Israel, South Africa and other ISE Countries +41 52 675 3777 Definition Video Poster Belgium* 00800 2255 4835 Brazil +55 (11) 3759 7627 This poster provides graphical Canada 1 (800) 833-9200 reference to understanding Central East Europe and the Baltics +41 52 675 3777 high definition video. Central Europe & Greece +41 52 675 3777 Denmark +45 80 88 1401 Finland +41 52 675 3777 France* 00800 2255 4835 To order your free copy of this poster, please visit: Germany* 00800 2255 4835 www.tek.com/poster/understanding-hd-and-3g-sdi-video-poster Hong Kong 400-820-5835 India 000-800-650-1835 Italy* 00800 2255 4835 Japan 81 (3) 6714-3010 Luxembourg +41 52 675 3777 MPEG-2 Transport Stream Advanced Television Systems Committee (ATSC) Mexico, Central/South America & Caribbean 52 (55) 56 04 50 90 ISO/IEC 13818-1 International Standard Program and System Information Protocol (PSIP) for Terrestrial Broadcast and cable (Doc. A//65B and A/69) System Time Table (STT) Rating Region Table (RRT) Direct Channel Change Table (DCCT) ISO/IEC 13818-2 Video Levels and Profiles MPEG Poster ISO/IEC 13818-1 Transport Packet PES PACKET SYNTAX DIAGRAM 24 bits 8 bits 16 bits Syntax Bits Format Syntax Bits Format Syntax Bits Format 4:2:0 4:2:2 4:2:0, 4:2:2 1920x1152 1920x1088 1920x1152 Packet PES Optional system_time_table_section(){ rating_region_table_section(){ directed_channel_change_table_section(){ High Syntax
    [Show full text]
  • "(222A. A772AMMAY Sept
    Sept. 29, 1959 L. DIETCH 2,906,814 SIGNAL OPERATED AUTOMATIC COLOR KILLER SYSTEM Filed April 28, l955 2. Sheets-Sheet l AAW22 a a2 aa’ a2/2 ass 122A 2 ASAf MaaZ AVA272M 77AAF42 4. A (So a 72.7 3.39 M269 22 66 (ol) (4) (C) -- - - - Hí2.É.-aws7 (a) A38 INVENTOR. Aawaz A7cay Aza y "(222a. A772AMMAY Sept. 29, 1959 L, DIETCH 2,906,814 SIGNAL OPERATED AUTOMATIC COLOR KILLER SYSTEM Filed April 28, 1955 2 Sheets-Sheet 2 |- 2,906,814 United States Patent Office Patented Sept. 29, 1959 1. 2 the phase of the sync bursts with the phase of the locally produced wave to derive a correction voltage for con trolling the frequency and phase of the oscillator which 2,906,814 produces the reference wave at the receiver. It is SIGNAL OPERATED AUTOMATIC COLOR desirable that synchronization of the receiver's color KILLERSYSTEM reference oscillator have been effected before the chro minance channel is activated, in order to prevent the Leonard Dietch, Haddonfield, N.J., assignor to Radio production of spurious color information pending such Corporation of America, a corporation of Delaware synchronization. Application April 28, 1955, Serial No. 504,503 O It is, therefore, a primary object of the present inven tion to provide new and improved automatic color chan 4 Claims. (C. 178-5.4) nel disabling means. Another object of the invention is the provision of automatic color channel disabling means, the operation The present invention relates to circuitry for automati 15 of which is correlated with the action of the receiver cally switching between two modes of operation and, color.
    [Show full text]
  • Tv Signal Processor for Multi System
    To our customers, Old Company Name in Catalogs and Other Documents On April 1st, 2010, NEC Electronics Corporation merged with Renesas Technology Corporation, and Renesas Electronics Corporation took over all the business of both companies. Therefore, although the old company name remains in this document, it is a valid Renesas Electronics document. We appreciate your understanding. Renesas Electronics website: http://www.renesas.com April 1st, 2010 Renesas Electronics Corporation Issued by: Renesas Electronics Corporation (http://www.renesas.com) Send any inquiries to http://www.renesas.com/inquiry. Notice 1. All information included in this document is current as of the date this document is issued. Such information, however, is subject to change without any prior notice. Before purchasing or using any Renesas Electronics products listed herein, please confirm the latest product information with a Renesas Electronics sales office. Also, please pay regular and careful attention to additional and different information to be disclosed by Renesas Electronics such as that disclosed through our website. 2. Renesas Electronics does not assume any liability for infringement of patents, copyrights, or other intellectual property rights of third parties by or arising from the use of Renesas Electronics products or technical information described in this document. No license, express, implied or otherwise, is granted hereby under any patents, copyrights or other intellectual property rights of Renesas Electronics or others. 3. You should not alter, modify, copy, or otherwise misappropriate any Renesas Electronics product, whether in whole or in part. 4. Descriptions of circuits, software and other related information in this document are provided only to illustrate the operation of semiconductor products and application examples.
    [Show full text]
  • Creating 4K/UHD Content Poster
    Creating 4K/UHD Content Colorimetry Image Format / SMPTE Standards Figure A2. Using a Table B1: SMPTE Standards The television color specification is based on standards defined by the CIE (Commission 100% color bar signal Square Division separates the image into quad links for distribution. to show conversion Internationale de L’Éclairage) in 1931. The CIE specified an idealized set of primary XYZ SMPTE Standards of RGB levels from UHDTV 1: 3840x2160 (4x1920x1080) tristimulus values. This set is a group of all-positive values converted from R’G’B’ where 700 mv (100%) to ST 125 SDTV Component Video Signal Coding for 4:4:4 and 4:2:2 for 13.5 MHz and 18 MHz Systems 0mv (0%) for each ST 240 Television – 1125-Line High-Definition Production Systems – Signal Parameters Y is proportional to the luminance of the additive mix. This specification is used as the color component with a color bar split ST 259 Television – SDTV Digital Signal/Data – Serial Digital Interface basis for color within 4K/UHDTV1 that supports both ITU-R BT.709 and BT2020. 2020 field BT.2020 and ST 272 Television – Formatting AES/EBU Audio and Auxiliary Data into Digital Video Ancillary Data Space BT.709 test signal. ST 274 Television – 1920 x 1080 Image Sample Structure, Digital Representation and Digital Timing Reference Sequences for The WFM8300 was Table A1: Illuminant (Ill.) Value Multiple Picture Rates 709 configured for Source X / Y BT.709 colorimetry ST 296 1280 x 720 Progressive Image 4:2:2 and 4:4:4 Sample Structure – Analog & Digital Representation & Analog Interface as shown in the video ST 299-0/1/2 24-Bit Digital Audio Format for SMPTE Bit-Serial Interfaces at 1.5 Gb/s and 3 Gb/s – Document Suite Illuminant A: Tungsten Filament Lamp, 2854°K x = 0.4476 y = 0.4075 session display.
    [Show full text]
  • Spectral Primary Decomposition for Rendering with RGB Reflectance
    Eurographics Symposium on Rendering (DL-only Track) (2019) T. Boubekeur and P. Sen (Editors) Spectral Primary Decomposition for Rendering with sRGB Reflectance Ian Mallett1 and Cem Yuksel1 1University of Utah Ground Truth Our Method Meng et al. 2015 D65 Environment 35 Error (Noise & Imprecision) Error (Color Distortion) E D CIE76 0:0 Lambertian Plane Figure 1: Spectral rendering of a texture containing the entire sRGB gamut as the Lambertian albedo for a plane under a D65 environment. In this configuration, ideally, rendered sRGB pixels should match the texture’s values. Prior work by Meng et al. [MSHD15] produces noticeable color distortion, whereas our method produces no error beyond numerical precision and Monte Carlo sampling noise (the magnitude of the DE induced by this noise varies with the image because sRGB is perceptually nonlinear). Contemporary work [JH19] is also nearly able to achieve this, but at a significant implementation and memory cost. Abstract Spectral renderers, as-compared to RGB renderers, are able to simulate light transport that is closer to reality, capturing light behavior that is impossible to simulate with any three-primary decomposition. However, spectral rendering requires spectral scene data (e.g. textures and material properties), which is not widely available, severely limiting the practicality of spectral rendering. Unfortunately, producing a physically valid reflectance spectrum from a given sRGB triple has been a challenging problem, and indeed until very recently constructing a spectrum without colorimetric round-trip error was thought to be impos- sible. In this paper, we introduce a new procedure for efficiently generating a reflectance spectrum from any given sRGB input data.
    [Show full text]
  • Chromatic Adaptation Transform by Spectral Reconstruction Scott A
    Chromatic Adaptation Transform by Spectral Reconstruction Scott A. Burns, University of Illinois at Urbana-Champaign, [email protected] February 28, 2019 Note to readers: This version of the paper is a preprint of a paper to appear in Color Research and Application in October 2019 (Citation: Burns SA. Chromatic adaptation transform by spectral reconstruction. Color Res Appl. 2019;44(5):682-693). The full text of the final version is available courtesy of Wiley Content Sharing initiative at: https://rdcu.be/bEZbD. The final published version differs substantially from the preprint shown here, as follows. The claims of negative tristimulus values being “failures” of a CAT are removed, since in some circumstances such as with “supersaturated” colors, it may be reasonable for a CAT to produce such results. The revised version simply states that in certain applications, tristimulus values outside the spectral locus or having negative values are undesirable. In these cases, the proposed method will guarantee that the destination colors will always be within the spectral locus. Abstract: A color appearance model (CAM) is an advanced colorimetric tool used to predict color appearance under a wide variety of viewing conditions. A chromatic adaptation transform (CAT) is an integral part of a CAM. Its role is to predict “corresponding colors,” that is, a pair of colors that have the same color appearance when viewed under different illuminants, after partial or full adaptation to each illuminant. Modern CATs perform well when applied to a limited range of illuminant pairs and a limited range of source (test) colors. However, they can fail if operated outside these ranges.
    [Show full text]
  • ARC Laboratory Handbook. Vol. 5 Colour: Specification and Measurement
    Andrea Urland CONSERVATION OF ARCHITECTURAL HERITAGE, OFARCHITECTURALHERITAGE, CONSERVATION Colour Specification andmeasurement HISTORIC STRUCTURESANDMATERIALS UNESCO ICCROM WHC VOLUME ARC 5 /99 LABORATCOROY HLANODBOUOKR The ICCROM ARC Laboratory Handbook is intended to assist professionals working in the field of conserva- tion of architectural heritage and historic structures. It has been prepared mainly for architects and engineers, but may also be relevant for conservator-restorers or archaeologists. It aims to: - offer an overview of each problem area combined with laboratory practicals and case studies; - describe some of the most widely used practices and illustrate the various approaches to the analysis of materials and their deterioration; - facilitate interdisciplinary teamwork among scientists and other professionals involved in the conservation process. The Handbook has evolved from lecture and laboratory handouts that have been developed for the ICCROM training programmes. It has been devised within the framework of the current courses, principally the International Refresher Course on Conservation of Architectural Heritage and Historic Structures (ARC). The general layout of each volume is as follows: introductory information, explanations of scientific termi- nology, the most common problems met, types of analysis, laboratory tests, case studies and bibliography. The concept behind the Handbook is modular and it has been purposely structured as a series of independent volumes to allow: - authors to periodically update the
    [Show full text]
  • 1966 1967 Color
    A HOWARD W. SAMS PUBLICATION NOVEMBER 1966150¢ PF Reporter® the magazine of electronic servicing r 1966 JANUARY AUGUST 2,400,000 color sets sold Know Your 1967 Color Circuits r 1 Servicing Bandpass Amplifiers L . r r plus... 01101,;aa t;It,rA r.u-)V3 ,a.,,,1- .3 Color Chaos A:.; Remote Control Pay TV 7: 3, '; v`. _ 3 r, ^ki New Tube & Transistor Data l FARALc'GR riazi, Improves Color Reception Three Ways 1. Plus GAIN-to provide sharper directivity to Plus -300 and 75 ohm outputs for match to either eliminate multipath reception. twinlead or coax. And full, flat gain over the entire FM band. 2. Plus FLATNESS-to eliminate tilts which cause incorrect colors on the TV screen. Industry Plus these quality mechanical features: Self-clean- experts say that color antennas must be flat within ing wedge -snap locks that tighten with vibration, ±2 db. Paralog-Plus antennas are flat within +1 Cycolac insulators to eliminate cumbersome cross db per channel. feed points, Golden Armor coating, Square boom construction, One-piece antenna array-and more. 3. Plus MATCH -to prevent color -distorting phase shifts. Check on how these plus features can help make plus profits for you. See your Jerrold distributor, The unique feature of the Paralog-Plus is a or write: BI MODAL DIRECTOR system. Its parasitic ele- ments combine two hi -band directors into a single director covering all to -band channels, plus the DISTRIBUTOR SALES DIVISION entire FM band. Thus, more of the elements work 401 Walnut St., Phila., Pa. 19105 to bring in any given channel.
    [Show full text]
  • TW9900 Data Short
    DATA SHORT To request the full datasheet, please visit www.intersil.com/products/TW9900 TW9900 FN7767 Low Power NTSC/PAL/SECAM Video Decoder with VBI Slicer Rev 5.00 April 7, 2016 The TW9900 is a low power NTSC/PAL/SECAM video decoder Features chip that is designed for portable applications. It consumes less than 100mW in typical composite input applications. The Video Decoder available power-down mode further reduces the power consumption. It uses the 1.8V for both analog and digital • NTSC (M, 4.43) and PAL (B, D, G, H, I, M, N, N combination), supply voltage and 3.3V for I/O power. A single 27MHz crystal PAL (60), SECAM support with automatic format detection is all that is needed to decode all analog video standards. • Software selectable analog inputs allow any of the following The video decoder decodes the baseband analog CVBS or combinations, e.g., 2 CVBS or 1 Y/C S-video signals into digital 8-bit 4:2:2 YCbCr for output. It • Built-in analog anti-alias filter consists of analog front-end with input source selection, • Two 10-bit ADCs and analog clamping circuit variable gain amplifier and analog-to-digital converters, Y/C separation circuit, multi-standard color decoder (PAL BGHI, • Fully programmable static gain or automatic gain control for PAL M, PAL N, combination PAL N, NTSC M, NTSC 4.43 and the Y-channel SECAM) and synchronization circuitry. The Y/C separation is • Programmable white peak control for the Y-channel done with high quality adaptive 4H comb filter for reduced • 4-H adaptive comb filter Y/C separation cross color and cross luminance.
    [Show full text]
  • Major Color Order Systems and Their Psychophysical Structure
    Chapter 7 Major Color Order Systems and Their Psychophysical Structure In this chapter only the Munsell, OSA-UCS, and Swedish NCS systems will be discussed. The former two are the most important attempts to create psy- chologically uniform systems, the latter uses the presumed natural approach of Hering (see Chapter 2) to create a color order system, having a regular structure, but not one uniform in terms of size of perceived differences. There are several other newer color order systems extant, but they neither make claims for uniformity nor for regularity according to new, significant psycho- logical attributes. The issue of viewing conditions for these systems has been attended to in different ways.As discussed previously,the Munsell system is illustrated as if the chips at each value level would be viewed against an achromatic surround of the same value.Chips of two adjacent value levels are illustrated as if viewed against an achromatic surround of intermediate value. The actual atlas displays the chips on white paper (historically of various degrees of whiteness), thus result- ing in distortions of the value scale, particularly at lower values.The OSA-UCS system is defined for an achromatic surround of luminous reflectance Y = 30 (L = 0).The atlas samples are in transparent jackets.NCS,finally,has been estab- lished against an immediate achromatic surround of Y = 78 in a light booth painted with an achromatic gray of Y = 54.The atlas displays samples on white paper. Both latter systems only result in the intended color experiences when viewed against the appropriate surrounds. Munsell and NCS are defined for Color Space and Its Divisions: Color Order from Antiquity to the Present, by Rolf G.
    [Show full text]
  • PRECISE COLOR COMMUNICATION COLOR CONTROL from PERCEPTION to INSTRUMENTATION Knowing Color
    PRECISE COLOR COMMUNICATION COLOR CONTROL FROM PERCEPTION TO INSTRUMENTATION Knowing color. Knowing by color. In any environment, color attracts attention. An infinite number of colors surround us in our everyday lives. We all take color pretty much for granted, but it has a wide range of roles in our daily lives: not only does it influence our tastes in food and other purchases, the color of a person’s face can also tell us about that person’s health. Even though colors affect us so much and their importance continues to grow, our knowledge of color and its control is often insufficient, leading to a variety of problems in deciding product color or in business transactions involving color. Since judgement is often performed according to a person’s impression or experience, it is impossible for everyone to visually control color accurately using common, uniform standards. Is there a way in which we can express a given color* accurately, describe that color to another person, and have that person correctly reproduce the color we perceive? How can color communication between all fields of industry and study be performed smoothly? Clearly, we need more information and knowledge about color. *In this booklet, color will be used as referring to the color of an object. Contents PART I Why does an apple look red? ········································································································4 Human beings can perceive specific wavelengths as colors. ························································6 What color is this apple ? ··············································································································8 Two red balls. How would you describe the differences between their colors to someone? ·······0 Hue. Lightness. Saturation. The world of color is a mixture of these three attributes.
    [Show full text]
  • Standard Illuminant
    Standard illuminant From Wikipedia, the free encyclopedia A standard illuminant is a profile or spectrum of visible light which is published in order to allow images or colors recorded under different lighting to be compared. Contents 1 CIE illuminants 1.1 Illuminant A 1.2 Illuminants B and C 1.3 Illuminant series D 1.4 Illuminant E Relative spectral power distributions (SPDs) of CIE 1.5 Illuminant series F illuminants A, B, and C from 380nm to 780nm. 2 White point 2.1 White points of standard illuminants 3 References 4 External links CIE illuminants The International Commission on Illumination (usually abbreviated CIE for its French name) is the body responsible for publishing all of the well-known standard illuminants. Each of these is known by a letter or by a letter-number combination. Illuminants A, B, and C were introduced in 1931, with the intention of respectively representing average incandescent light, direct sunlight, and average daylight. Illuminants D represent phases of daylight, Illuminant E is the equal-energy illuminant, while Illuminants F represent fluorescent lamps of various composition. There are instructions on how to experimentally produce light sources ("standard sources") corresponding to the older illuminants. For the relatively newer ones (such as series D), experimenters are left to measure to profiles of their sources and compare them to the published spectra:[1] At present no artificial source is recommended to realize CIE standard illuminant D65 or any other illuminant D of different CCT. It is hoped that new developments in light sources and filters will eventually offer sufficient basis for a CIE recommendation.
    [Show full text]