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Item 3.2 - Additional Material posted 1-16-191 Ana Alarcon From:Carol Legg Sent:Tuesday, January 15, 2019 6:02 PM To:Kay Vinson; Ana Alarcon; Jasmine Pernicano Cc:Bob Manis Subject:FW: Item 3.2, 1/15/19 Poway City Council Meeting Attachments:Lighting Solutions _ Lighting Solutions.pdf; Low Pressure Sodium Light Bulbs _ Bulbs.com.pdf; Color_temperature.pdf For tonight’s meeting. It already went to the Councilmembers and to tina. From: Peter De Hoff <pldehoff@gmail.com> Sent: Tuesday, January 15, 2019 5:52 PM To: Steve Vaus <SVaus@poway.org>; John Mullin <JMullin@poway.org>; Dave Grosch <DGrosch@poway.org>; Barry Leonard <BLeonard@poway.org>; Caylin Frank <CFrank@poway.org> Cc: Tina White <TWhite@poway.org> Subject: Re: Item 3.2, 1/15/19 Poway City Council Meeting To City Council, This is a slight repeat of the previous email where I have attached .pdf files of the various web links I provided before. This is only for the case you were, for whatever reason, unable to click on those links in the earlier email. If you were able to click on them, then there is nothing new here. Sorry for the lateness of this, but it just occurred to me. Regards, Peter De Hoff > On Jan 12, 2019, at 8:57 PM, Peter De Hoff <pldehoff@gmail.com> wrote: > > To City Council, > This is in regards to the upcoming January 15th City Council meeting Item 3.2 regarding upgrading the current LPS streetlights to LEDs. I have written on this before essentially noting that the lights in the Montego Road test area are most similar in color temperature as to our current low pressure sodium (LPS) lamps and that I prefer them for various reasons, mostly related to that choice having the least impact in terms of light pollution and light spillage. The second choice being the lights in the test area on Garden Road. I came across an article (attached) in the Journal Science, which is the premier peer reviewed science journal in the United States, that may be of relevance to this issue. This is an “Insights” article and does not contain much in the way of technical jargon. If you have the time, you might find it enlightening. The take home message is best summed up in the quote “Of particular concern is the growth in emissions of blue wavelengths…”, but there is a great deal of relevant information encompassed within the ~3 pages of text. > Essentially, the blue light that makes up part of the white LED light spectrum has a much higher propensity to scatter, irrespective of shielding. For the same reason our skies are blue in the day and red in the evening, the shorter the wavelength of light (ie bluer) the more of it will scatter out of the valleys, and over the surrounding hills. This leads to “sky glow” miles away from the source, as well as the oversized impact of the bluer light on the surrounding flora and fauna (including humans). > While there do exist filtered LEDs that remove almost all of the shorter blue wavelengths from the bulb’s light spectrum, as of yet I do not know the part numbers of the LEDs being used in these tests, so I do not know if they are filtered in such a manner. Although that question is only relevant for the lights on Garden and Montego Roads as all of the other lights are definitely unfiltered in this regard. > > Of particular technical relevance to the staff is the following: > ADDITIONAL MATERIAL 1 of 25 January 15, 2019, Item # 3.2 2 > I noticed near the end of the text agenda item in the Environmental Review Section where it mentions the replacement lights will have “an equivalent or reduced color temperature.” I think it is important to note that the current Low Pressure Sodium (LPS) fixtures have a color temperature of 1700K, which was not made clear in the upper section of the text of the agenda item. As far as I know, in Poway at least, these LPS lights are the only types of lighting used in all of the streetlights, including those that sit atop of street signal light fixtures. Also, that none of the test LED lights, with the possible exception of those lights on Montego Road, have a color spectrum at or below 1700K. > There do exist High Pressure Sodium (HPS) lamps with color temperatures around 2700K and it is possible that LPS and HPS lights are being conflated in the case of the agenda text. I do apologize for not pointing this out earlier, but I just read the agenda item tonight. You can see in these two links below the description of LPS lights having a color temperature of 1700K. > > Near the bottom of this link – search “LPS” > https://en.wikipedia.org/wiki/Color_temperature > > The link below is for purchasing LPS lights and describes their color temperature (all at 1700K) > https://www.bulbs.com/Low_Pressure_Sodium‐High_Intensity_Discharge_(HID)‐Light_Bulbs‐Category/results.aspx > > As I implied earlier, I do not recall the color temperature of the amber lights on the Montego Road test area, but I suspect they are close to 1700K. Regardless, I do know there are streetlight products available that essentially replicate the 1700K of the LPS lights. (see the link below) > > https://www.osram.com/ls/news/amber/index.jsp > > I will be coming by on Tuesday to make a short oral presentation on this matter, mostly focusing on the choice of color of the LED fixtures. See you then. > > Best Regards, > > Peter De Hoff > <171116_Science_LED_Lighting.pdf> > 2 of 25 January 15, 2019, Item # 3.2 1/15/2019 Lighting Solutions | Lighting Solutions https://www.osram.com/ls/news/amber/index.jsp 1/5 Make the most of amber-colored LED light in Urban Lighting Orange Light:Orange Light:Orange Light: Safety, Design and EnvironmentalSafety, Design and EnvironmentalSafety, Design and Environmental ProtectionProtectionProtection For a long time orange-colored light was used in urban lighting in the form of high/low pressure sodium vapor lamps. With the modernization to LED technology and the ban on most conventional ballasts valid since this year, this light color has almost completely disappeared from the product catalogue of most manufacturers. The OSRAM company Siteco is now adding orange-colored light to a part of its LED outdoor luminaire portfolio because this offers significant advantages in certain areas compared to the familiar white light of LED technology. That's why it makes sense to use it in the following areas: 1) Illumination of conflict areas: Lighting Solutions 3 of 25 January 15, 2019, Item # 3.2 1/15/2019 Lighting Solutions | Lighting Solutions https://www.osram.com/ls/news/amber/index.jsp 2/5 Conflict areas are e.g. crossings, crosswalks or crossing aids for pedestrians. Ensures safety - as traffic’s attention is brought to the conflict zone? The increased attention decreases the probability of an accident 2) Design with light: The selected light color influences the appearance of the illuminated material. Thus the appearance of the material can be influenced positively or negatively.?Amber colored light is ideally suited for illuminating buildings with a brick or sandstone facade because the warm light color emphasizes the warm fundamental tone of the facade. It is less suitable for concrete, glass or limestone facades. 3) Modernization of lighting systems: Because of the conversion to LED, a different light image is created. In rare cases residents are feeling disturbed by the new lighting installation. Municipalities that want to have a similar light image can use LED lamps with amber-colored light as it works a good alternative to the sodium-vapor high/low-pressure lamps. 4) Reduction of light pollution In clear air, short-wave blue light is diffused much further than long-wave red light. That is why the daytime sky appears blue. That means: The higher the blue light content of the light source, the higher is the scatter in all directions > higher light pollution. 5) Protect the environment: 4 of 25 January 15, 2019, Item # 3.2 1/15/2019 Lighting Solutions | Lighting Solutions https://www.osram.com/ls/news/amber/index.jsp 3/5 LEDs are free of IR and UV radiation. This makes them very "insect-friendly" and therefore environmentally friendly. Also the light color plays a role. Insects are less attracted to the yellowish light of a sodium vapor high/low-pressure lamp than the white light of a high-pressure mercury lamp.?Even when looking at the LED, the 3000K variant attracts far less insects than the version with 6000K. An even warmer light color of the LED promises further improvement. In areas which are particularly vulnerable, such as in natural or national parks or near waterways (cannels with ship locks), the use can be useful. We offer these products: Documents available on request Streetlight 20: A complete family — micro: 2.500 lm* — mini: 5.000 lm* — midi: 10.000lm* — *lumen packages with constant lumen output 2 light distributions — ST0.5a — ST1.0a — PC-L and R on request (for crosswalks) Light color — Amber: 1750K — >50 (57) SL20 micro 4058352102220 5XB15DAB108B ST0.5a Plu SL20 mini 4058352102282 5XB25HAB308B ST0.5a Plu SL20 midi 4058352104873 5XB35MAB408B ST0.5a Plu Type EAN Siteco order code Light distribution Co 5 of 25 January 15, 2019, Item # 3.2 1/15/2019 Lighting Solutions | Lighting Solutions https://www.osram.com/ls/news/amber/index.jsp 4/5 SL20 micro 4058352102183 5XB11DAB108B ST1.0a Plu SL20 mini 4058352102244 5XB21HAB308B ST1.0a Plu SL20 midi 4058352104859 5XB31MAB408B ST1.0a Plu Type EAN Siteco order code Light distribution Co Order number: 5XA54000XSA - Upgradable without tools All lantern shaped luminaires with LED Modul 540: Amber-colored light with accessories Amber-Spreader- Element A complete family in Amber — Suitable for 10 different housing designs — With various lumen packages — With CLO2.0 — Three light distributions (ST1.2A, P1.0A, PL1.2S) Light technical data — CRI 50 — Color temperature: 4000K becomes 2200K 3000K becomes 1900K Floodlight 20 (on request): Suitable for many different applications — 4 housing sizes — 7 light distribution – rotationally symmetrical (suitable for facade illumination)6 of 25 January 15, 2019, Item # 3.2 1/15/2019 Lighting Solutions | Lighting Solutions https://www.osram.com/ls/news/amber/index.jsp 5/5 — Diverse mounting options — Also usable as up light Light technical data — CRI >50 (57) — Color temperature: ~1750K Do you need more information? For further information like local representatives or product documentation, please contact us. 7 of 25 January 15, 2019, Item # 3.2 1/15/2019 Low Pressure Sodium Light Bulbs | Bulbs.com https://www.bulbs.com/Low_Pressure_Sodium-High_Intensity_Discharge_(HID)-Light_Bulbs-Category/results.aspx 1/4 Sort By: Most Popular Page 1 of 1 6 results Category Light Bulbs › HID › Low Pressure Sodium Low Pressure Sodium Light Bulbs ON SALE D. C. Bayonet, Medium (BY22D) Base 1800 Lumens Warm White Bulb Color 1700K Color Temperature 2.1" Diameter 18W Energy Used 8.5" Length T-17 Shape More details Philips 18W T17 Low Pressure Sodium Bulb Double Contact Bayonet Base SKU: 234047 | Ordering Code: SOX-E18 | UPC: 8711500600097 Select to compare $59.99 $47.99 per bulb You save 20% 1 Bulb ADD TO CART ON SALE D. C. 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Bayonet, Medium (BY22D) Base 4550 Lumens Warm White Bulb Color 1700K Color Temperature 2.1" Diameter 35W Energy Used 12.2" Length T-17 Shape More details Philips 35W T17 Clear Low Pressure Sodium SOX Bulb SKU: 327817 | Ordering Code: SOX35 | UPC: 8711500179739 Select to compare (1 review) $59.99 $47.99 per bulb You save 20% 1 Bulb ADD TO CART ON SALE D. C. Bayonet, Medium (BY22D) Base 12155 Lumens Warm White Bulb Color 1700K Color Temperature 2.6" Diameter 90W Energy Used 20.8" Length T-21 Shape More details Philips 90W T21 Clear Low Pressure Sodium SOX Bulb SKU: 321521 | Ordering Code: SOX90 | UPC: 8711500600158 Select to compare $69.99 $55.99 per bulb You save 20% 1 Bulb ADD TO CART Philips 135W T21 Clear Low Pressure Sodium SOX Bulb SKU: 321539 | Ordering Code: SOX135 | UPC: 8711500179791 $87.49 $69.99 per bulb You save 20% 1 Bulb 9 of 25 January 15, 2019, Item # 3.2 1/15/2019 Low Pressure Sodium Light Bulbs | Bulbs.com https://www.bulbs.com/Low_Pressure_Sodium-High_Intensity_Discharge_(HID)-Light_Bulbs-Category/results.aspx 3/4 Sign up to receive our best offers example@youremail.com SUBSCRIBE Stay connected with Bulbs.com Trusted Partners Company Info About Us Our Promise Our Lighting Specialists Testimonials Case Studies Press Room Business Center Pro Business Account Shop By Business Type Your Lighting Project Lighting Rebates Customer Service Contact Us FAQs Privacy Policy Terms of Sale Shipping Policy Resources The Learning Center Energy Savings Calculator Base, Shape and Filament Reference Charts Page 1 of 1 ON SALE D. 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Bayonet, Medium (BY22D) Base 32000 Lumens Warm White Bulb Color 1700K Color Temperature 2.6" Diameter 180W Energy Used 44.1" Length T-21 Shape More details Philips 180W T21 Clear Low Pressure Sodium SOX Bulb SKU: 151167 | Ordering Code: SOX180 | UPC: 8711500600073 Select to compare $137.49 $115.99 per bulb You save 15% 1 Bulb ADD TO CART 10 of 25 January 15, 2019, Item # 3.2 1/15/2019 Low Pressure Sodium Light Bulbs | Bulbs.com https://www.bulbs.com/Low_Pressure_Sodium-High_Intensity_Discharge_(HID)-Light_Bulbs-Category/results.aspx 4/4 Try LED Risk-free Credit Application International Customers Returns and Exchanges BulbTrack Overview Blogs The Light Source Current News 1-888-455-2800 Email Us Accepted Payments 11 of 25 January 15, 2019, Item # 3.2 Color temperature Not to be confused with warm and cool colors. The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of a color comparable to that of the light source. Color temperature is a characteristic of visible light that has important applications in lighting, photography, videography, publishing, manufacturing, astrophysics, horticulture, and other fields. In practice, color temperature is meaningful only for light sources that do in fact correspond somewhat closely to the radiation of some black body, i.e., light in a range going from red to orange to yellow to white to blueish white; it does not make sense to speak of the color temperature of, e.g., a green or a purple light. Color temperature is conventionally expressed in kelvin, using the symbol K, a unit of measure for absolute temperature. Color temperatures over 5000 K are called "cool colors" (bluish), while lower color temperatures (2700–3000 K) are called "warm colors" (yellowish). "Warm" in this context is an analogy to radiated heat flux of traditional incandescent lighting rather than temperature. The spectral peak of warm-coloured light is closer to infrared, and most natural warm-coloured light sources emit significant infrared radiation. The fact that "warm" lighting in this sense actually has a "cooler" color temperature often leads to confusion.[1] Categorizing different lighting The Sun Applications Lighting Aquaculture Digital photography Photographic film Desktop publishing TV, video, and digital still cameras Artistic application via control of color temperature Correlated color temperature Motivation Background Calculation Robertson's method Precautions Approximation Color rendering index Spectral power distribution The CIE 1931 x,y chromaticity space, also showing the chromaticities of black-body light sources of various temperatures (Planckian locus), and lines of constant correlated color temperature. Contents 12 of 25 January 15, 2019, Item # 3.2 Temperature Source 1700 K Match flame, low pressure sodium lamps (LPS/SOX) 1850 K Candle flame, sunset/sunrise 2400 K Standard incandescent lamps 2550 K Soft white incandescent lamps 2700 K "Soft white" compact fluorescent and LED lamps 3000 K Warm white compact fluorescent and LED lamps 3200 K Studio lamps, photofloods, etc. 3350 K Studio "CP" light 5000 K Horizon daylight 5000 K Tubular fluorescent lamps or cool white / daylight compact fluorescent lamps (CFL) 5500 – 6000 K Vertical daylight, electronic flash 6200 K Xenon short-arc lamp [2] 6500 K Daylight, overcast 6500 – 9500 K LCD or CRT screen 15,000 – 27,000 K Clear blue poleward sky These temperatures are merely characteristic; there may be considerable variation Color temperature in astronomy See also References Further reading External links The color temperature of the electromagnetic radiation emitted from an ideal black body is defined as its surface temperature in kelvins, or alternatively in mireds (micro- reciprocal kelvins).[3] This permits the definition of a standard by which light sources are compared. To the extent that a hot surface emits thermal radiation but is not an ideal black-body radiator, the color temperature of the light is not the actual temperature of the surface. An incandescent lamp's light is thermal radiation, and the bulb approximates an ideal black-body radiator, so its color temperature is essentially the temperature of the filament. Thus a relatively low temperature emits a dull red and a high temperature emits the almost white of the traditional incandescent light bulb. Metal workers are able to judge the temperature of hot metals by their color, from dark red to orange-white and then white (see red heat). Many other light sources, such as fluorescent lamps, or LEDs (light emitting diodes) emit light primarily by processes other than thermal radiation. This means that the emitted radiation does not follow the form of a black-body spectrum. These sources are assigned what is known as a correlated color temperature (CCT). CCT is the color temperature of a black-body radiator which to human color perception most closely matches the light from the lamp. Because such an approximation is not required for incandescent light, the CCT for an incandescent light is simply its unadjusted temperature, derived from comparison to a black-body radiator. Categorizing different lighting The black-body radiance (Bλ) vs. wavelength (λ) curves for the visible spectrum. The vertical axes of Planck's law plots building this animation were proportionally transformed to keep equal areas between functions and horizontal axis for wavelengths 380–780 nm. 13 of 25 January 15, 2019, Item # 3.2 The Sun closely approximates a black-body radiator. The effective temperature, defined by the total radiative power per square unit, is about 5780 K.[4] The color temperature of sunlight above the atmosphere is about 5900 K.[5] As the Sun crosses the sky, it may appear to be red, orange, yellow or white, depending on its position. The changing color of the Sun over the course of the day is mainly a result of the scattering of light and is not due to changes in black-body radiation. The blue color of the sky is caused by Rayleigh scattering of the sunlight by the atmosphere, which tends to scatter blue light more than red light. Some early morning and evening light (golden hours) has a lower color temperature due to increased low-wavelength light scattering by the Tyndall effect. Daylight has a spectrum similar to that of a black body with a correlated color temperature of 6500 K (D65 viewing standard) or 5500 K (daylight-balanced photographic film standard). Hues of the Planckian locus on a logarithmic scale For colors based on black-body theory, blue occurs at higher temperatures, whereas red occurs at lower temperatures. This is the opposite of the cultural associations attributed to colors, in which "red" is "hot", and "blue" is "cold".[6] For lighting building interiors, it is often important to take into account the color temperature of illumination. A warmer (i.e., a lower color temperature) light is often used in public areas to promote relaxation, while a cooler (higher color temperature) light is used to enhance concentration, for example in schools and offices.[7] CCT dimming for LED technology is regarded as a difficult task, since binning, age and temperature drift effects of LEDs change the actual color value output. Here feedback loop systems are used, for example with color sensors, to actively monitor and control the color output of multiple color mixing LEDs.[8] In fishkeeping, color temperature has different functions and foci in the various branches. In freshwater aquaria, color temperature is generally of concern only for producing a more attractive display. Lights tend to be designed to produce an attractive spectrum, sometimes with secondary attention paid to keeping the plants in the aquaria alive. In a saltwater/reef aquarium, color temperature is an essential part of tank health. Within about 400 to 3000 nanometers, light of shorter wavelength can penetrate deeper into water than longer wavelengths,[9][10][11] providing essential energy sources to the algae hosted in (and sustaining) coral. This is equivalent to an increase of color temperature with water depth in this spectral range. Because coral typically live in shallow water and receive intense, direct tropical sunlight, the focus was once on simulating this situation with 6500 K lights. In the meantime higher temperature light sources have become more popular, first with 10000 K and more recently 16000 K and 20000 K. The Sun Applications Lighting Color temperature comparison of common electric lampsAquaculture 14 of 25 January 15, 2019, Item # 3.2 Actinic lighting at the violet end of the visible range (420–460 nm) is used to allow night viewing without increasing algae bloom or enhancing photosynthesis, and to make the somewhat fluorescent colors of many corals and fish "pop", creating brighter display tanks. In digital photography, the term color temperature is sometimes used interchangeably with white balance, which allow a remapping of color values to simulate variations in ambient color temperature. Most digital cameras and raw image software provide presets simulating specific ambient values (e.g., sunny, cloudy, tungsten, etc.) while others allow explicit entry of white balance values in kelvins. These settings vary color values along the blue–yellow axis, while some software includes additional controls (sometimes labeled "tint") adding the magenta–green axis, and are to some extent arbitrary and a matter of artistic interpretation.[12] Use of absolute color temperature values are unlikely to be popular with digital photographers, as those with physical science backgrounds will note. However the general idea of high K (blue-white) and low K (red-orange) will inform all who seek to experiment with their own hardware and software. Photographic emulsion film does not respond to lighting color identically to the human retina or visual perception. An object that appears to the observer to be white may turn out to be very blue or orange in a photograph. The color balance may need to be corrected during printing to achieve a neutral color print. The extent of this correction is limited since color film normally has three layers sensitive to different colors and when used under the "wrong" light source, every layer may not respond proportionally, giving odd color casts in the shadows, although the mid-tones may have been correctly white-balanced under the enlarger. Light sources with discontinuous spectra, such as fluorescent tubes, cannot be fully corrected in printing either, since one of the layers may barely have recorded an image at all. Photographic film is made for specific light sources (most commonly daylight film and tungsten film), and, used properly, will create a neutral color print. Matching the sensitivity of the film to the color temperature of the light source is one way to balance color. If tungsten film is used indoors with incandescent lamps, the yellowish-orange light of the tungsten incandescent lamps will appear as white (3200 K) in the photograph. Color negative film is almost always daylight-balanced, since it is assumed that color can be adjusted in printing (with limitations, see above). Color transparency film, being the final artefact in the process, has to be matched to the light source or filters must be used to correct color. Filters on a camera lens, or color gels over the light source(s) may be used to correct color balance. When shooting with a bluish light (high color temperature) source such as on an overcast day, in the shade, in window light, or if using tungsten film with white or blue light, a yellowish-orange filter will correct this. For shooting with daylight film (calibrated to 5600 K) under warmer (low color temperature) light sources such as sunsets, candlelight or tungsten lighting, a bluish (e.g. #80A) filter may be used. More-subtle filters are needed to correct for the difference between, say 3200 K and 3400 K tungsten lamps or to correct for the slightly blue cast of some flash tubes, which may be 6000 K. If there is more than one light source with varied color temperatures, one way to balance the color is to use daylight film and place color-correcting gel filters over each light source. Photographers sometimes use color temperature meters. These are usually designed to read only two regions along the visible spectrum (red and blue); more expensive ones read three regions (red, green, and blue). However, they are ineffective with sources such as fluorescent or discharge lamps, whose light varies in color and may be harder to correct for. Because this light is often greenish, a magenta filter may correct it. More sophisticated colorimetry tools can be used if such meters are lacking. In the desktop publishing industry, it is important to know a monitor’s color temperature. Color matching software, such as Apple's ColorSync for Mac OS, measures a monitor's color temperature and then adjusts its settings accordingly. This enables on-screen color to more closely match printed color. Common monitor color temperatures, along with matching standard illuminants in parentheses, Digital photography Photographic film Desktop publishing 15 of 25 January 15, 2019, Item # 3.2 are as follows: 5000 K (D50) 5500 K (D55) 6500 K (D65) 7500 K (D75) 9300 K D50 is scientific shorthand for a standard illuminant: the daylight spectrum at a correlated color temperature of 5000 K. Similar definitions exist for D55, D65 and D75. Designations such as D50 are used to help classify color temperatures of light tables and viewing booths. When viewing a color slide at a light table, it is important that the light be balanced properly so that the colors are not shifted towards the red or blue. Digital cameras, web graphics, DVDs, etc., are normally designed for a 6500 K color temperature. The sRGB standard commonly used for images on the Internet stipulates (among other things) a 6500 K display white point. The NTSC and PAL TV norms call for a compliant TV screen to display an electrically black and white signal (minimal color saturation) at a color temperature of 6500 K. On many consumer-grade televisions, there is a very noticeable deviation from this requirement. However, higher-end consumer-grade televisions can have their color temperatures adjusted to 6500 K by using a preprogrammed setting or a custom calibration. Current versions of ATSC explicitly call for the color temperature data to be included in the data stream, but old versions of ATSC allowed this data to be omitted. In this case, current versions of ATSC cite default colorimetry standards depending on the format. Both of the cited standards specify a 6500 K color temperature. Most video and digital still cameras can adjust for color temperature by zooming into a white or neutral colored object and setting the manual "white balance" (telling the camera that "this object is white"); the camera then shows true white as white and adjusts all the other colors accordingly. White-balancing is necessary especially when indoors under fluorescent lighting and when moving the camera from one lighting situation to another. Most cameras also have an automatic white balance function that attempts to determine the color of the light and correct accordingly. While these settings were once unreliable, they are much improved in today's digital cameras and produce an accurate white balance in a wide variety of lighting situations. Video camera operators can white-balance objects that are not white, downplaying the color of the object used for white-balancing. For instance, they can bring more warmth into a picture by white-balancing off something that is light blue, such as faded blue denim; in this way white-balancing can replace a filter or lighting gel when those are not available. Cinematographers do not “white balance” in the same way as video camera operators; they use techniques such as filters, choice of film stock, pre-flashing, and, after shooting, color grading, both by exposure at the labs and also digitally. Cinematographers also work closely with set designers and lighting crews to achieve the desired color effects. For artists, most pigments and papers have a cool or warm cast, as the human eye can detect even a minute amount of saturation. Gray mixed with yellow, orange, or red is a “warm gray”. Green, blue, or purple create “cool grays”. Note that this sense of temperature is the reverse of that of real temperature; bluer is described as “cooler” even though it corresponds to a higher-temperature black body. Lighting designers sometimes select filters by color temperature, commonly to match light that is theoretically white. Since fixtures using discharge type lamps produce a light of a considerably higher TV, video, and digital still cameras Artistic application via control of color temperature The house above appears a light cream during midday, but seems to be bluish white here in the dim light before full sunrise. Note the color temperature of the sunrise in the background. 16 of 25 January 15, 2019, Item # 3.2 "Warm" gray "Cool" gray Mixed with 6% yellow. Mixed with 6% blue. color temperature than do tungsten lamps, using the two in conjunction could potentially produce a stark contrast, so sometimes fixtures with HID lamps, commonly producing light of 6000–7000 K, are fitted with 3200 K filters to emulate tungsten light. Fixtures with color mixing features or with multiple colors, (if including 3200 K) are also capable of producing tungsten-like light. Color temperature may also be a factor when selecting lamps, since each is likely to have a different color temperature. The correlated color temperature (CCT, Tcp) is the temperature of the Planckian radiator whose perceived color most closely resembles that of a given stimulus at the same brightness and under specified viewing conditions — CIE/IEC 17.4:1987, International Lighting Vocabulary (ISBN 3900734070)[13] Black-body radiators are the reference by which the whiteness of light sources is judged. A black body can be described by its color temperature, whose hues are depicted above. By analogy, nearly Planckian light sources such as certain fluorescent or high-intensity discharge lamps can be judged by their correlated color temperature (CCT), the color temperature of the Planckian radiator that best approximates them. For light source spectra that are not Planckian, color temperature is not a well defined attribute; the concept of correlated color temperature was developed to map such sources as well as possible onto the one-dimensional scale of color temperature, where "as well as possible" is defined in the context of an objective color space. The notion of using Planckian radiators as a yardstick against which to judge other light sources is not new.[14] In 1923, writing about "grading of illuminants with reference to quality of color ... the temperature of the source as an index of the quality of color", Priest essentially described CCT as we understand it today, going so far as to use the term "apparent color temperature", and astutely recognized three cases:[15] "Those for which the spectral distribution of energy is identical with that given by the Planckian formula." "Those for which the spectral distribution of energy is not identical with that given by the Planckian formula, but still is of such a form that the quality of the color evoked is the same as would be evoked by the energy from a Planckian radiator at the given color temperature." "Those for which the spectral distribution of energy is such that the color can be matched only approximately by a stimulus of the Planckian form of spectral distribution." Several important developments occurred in 1931. In chronological order: 1. Raymond Davis published a paper on "correlated color temperature" (his term). Referring to the Planckian locus on the r-g diagram, he defined the CCT as the average of the "primary component temperatures" (RGB CCTs), using trilinear coordinates.[16] 2. The CIE announced the XYZ color space. Correlated color temperature Log-log graphs of peak emission wavelength and radiant exitance vs black- body temperature – red arrows show that 5780 K black bodies have 501 nm peak wavelength and 63.3 MW/m² radiant exitance Motivation Background 17 of 25 January 15, 2019, Item # 3.2 3. Deane B. Judd published a paper on the nature of "least perceptible differences" with respect to chromatic stimuli. By empirical means he determined that the difference in sensation, which he termed ΔE for a "discriminatory step between colors ... Empfindung" (German for sensation) was proportional to the distance of the colors on the chromaticity diagram. Referring to the (r,g) chromaticity diagram depicted aside, he hypothesized that[17] KΔE = |c1 − c2| = max(|r1 − r2|, |g1 − g2|). These developments paved the way for the development of new chromaticity spaces that are more suited to estimating correlated color temperatures and chromaticity differences. Bridging the concepts of color difference and color temperature, Priest made the observation that the eye is sensitive to constant differences in "reciprocal" temperature:[18] A difference of one micro-reciprocal-degree (μrd) is fairly representative of the doubtfully perceptible difference under the most favorable conditions of observation. Priest proposed to use "the scale of temperature as a scale for arranging the chromaticities of the several illuminants in a serial order". Over the next few years, Judd published three more significant papers: The first verified the findings of Priest,[15] Davis,[16] and Judd,[17] with a paper on sensitivity to change in color temperature.[19] The second proposed a new chromaticity space, guided by a principle that has become the holy grail of color spaces: perceptual uniformity (chromaticity distance should be commensurate with perceptual difference). By means of a projective transformation, Judd found a more "uniform chromaticity space" (UCS) in which to find the CCT. Judd determined the "nearest color temperature" by simply finding the point on the Planckian locus nearest to the chromaticity of the stimulus on Maxwell's color triangle, depicted aside. The transformation matrix he used to convert X,Y,Z tristimulus values to R,G,B coordinates was:[20] From this, one can find these chromaticities:[21] The third depicted the locus of the isothermal chromaticities on the CIE 1931 x,y chromaticity diagram.[22] Since the isothermal points formed normals on his UCS diagram, transformation back into the xy plane revealed them still to be lines, but no longer perpendicular to the locus. Judd's idea of determining the nearest point to the Planckian locus on a uniform chromaticity space is current. In 1937, MacAdam suggested a "modified uniform chromaticity scale diagram", based on certain simplifying geometrical considerations:[23] Judd's (r,g) diagram. The concentric curves indicate the loci of constant purity. Judd's Maxwell triangle. Planckian locus in gray. Translating from trilinear co- ordinates into Cartesian co- ordinates leads to the next diagram. Calculation 18 of 25 January 15, 2019, Item # 3.2 This (u,v) chromaticity space became the CIE 1960 color space, which is still used to calculate the CCT (even though MacAdam did not devise it with this purpose in mind).[24] Using other chromaticity spaces, such as u'v', leads to non-standard results that may nevertheless be perceptually meaningful.[25] Judd's uniform chromaticity space (UCS), with the Planckian locus and the isotherms from 1000 K to 10000 K, perpendicular to the locus. Judd calculated the isotherms in this space before translating them back into the (x,y) chromaticity space, as depicted in the diagram at the top of the article. Close up of the Planckian locus in the CIE 1960 UCS, with the isotherms in mireds. Note the even spacing of the isotherms when using the reciprocal temperature scale and compare with the similar figure below. The even spacing of the isotherms on the locus implies that the mired scale is a better measure of perceptual color difference than the temperature scale. MacAdam's "uniform chromaticity scale" diagram; a simplification of Judd's UCS. 19 of 25 January 15, 2019, Item # 3.2 Close up of the CIE 1960 UCS. The isotherms are perpendicular to the Planckian locus, and are drawn to indicate the maximum distance from the locus that the CIE considers the correlated color temperature to be meaningful: The distance from the locus (i.e., degree of departure from a black body) is traditionally indicated in units of ; positive for points above the locus. This concept of distance has evolved to become Delta E, which continues to be used today. Before the advent of powerful personal computers, it was common to estimate the correlated color temperature by way of interpolation from look-up tables and charts.[26] The most famous such method is Robertson's,[27] who took advantage of the relatively even spacing of the mired scale (see above) to calculate the CCT Tc using linear interpolation of the isotherm's mired values:[28] where and are the color temperatures of the look-up isotherms and i is chosen such that . (Furthermore, the test chromaticity lies between the only two adjacent lines for which .) If the isotherms are tight enough, one can assume , leading to The distance of the test point to the i-th isotherm is given by where is the chromaticity coordinate of the i-th isotherm on the Planckian locus and mi is the isotherm's slope. Since it is perpendicular to the locus, it follows that where li is the slope of the locus at . Robertson's method Computation of the CCT Tc corresponding to the chromaticity coordinate in the CIE 1960 UCS. Precautions 20 of 25 January 15, 2019, Item # 3.2 Although the CCT can be calculated for any chromaticity coordinate, the result is meaningful only if the light sources are nearly white.[29] The CIE recommends that "The concept of correlated color temperature should not be used if the chromaticity of the test source differs more than [] from the Planckian radiator."[30] Beyond a certain value of , a chromaticity co-ordinate may be equidistant to two points on the locus, causing ambiguity in the CCT. If a narrow range of color temperatures is considered—those encapsulating daylight being the most practical case—one can approximate the Planckian locus in order to calculate the CCT in terms of chromaticity coordinates. Following Kelly's observation that the isotherms intersect in the purple region near (x = 0.325, y = 0.154),[26] McCamy proposed this cubic approximation:[31] CCT(x, y) = 449n3 + 3525n2 + 6823.3n + 5520.33, where n = (x − xe)/(y - ye) is the inverse slope line, and (xe = 0.3320, ye = 0.1858) is the "epicenter"; quite close to the intersection point mentioned by Kelly. The maximum absolute error for color temperatures ranging from 2856 K (illuminant A) to 6504 K (D65) is under 2 K. A more recent proposal, using exponential terms, considerably extends the applicable range by adding a second epicenter for high color temperatures:[32] CCT(x,y) = A0 + A1exp(−n/t1) + A2exp(−n/t2) + A3exp(−n/t3), where n is as before and the other constants are defined below: 3–50 kK 50–800 kK xe 0.3366 0.3356 ye 0.1735 0.1691 A0 −949.86315 36284.48953 A1 6253.80338 0.00228 t1 0.92159 0.07861 A2 28.70599 5.4535×10−36 t2 0.20039 0.01543 A3 0.00004 t3 0.07125 The inverse calculation, from color temperature to corresponding chromaticity coordinates, is discussed in Planckian locus. The CIE color rendering index (CRI) is a method to determine how well a light source's illumination of eight sample patches compares to the illumination provided by a reference source. Cited together, the CRI and CCT give a numerical estimate of what reference (ideal) light source best approximates a particular artificial light, and what the difference is. Light sources and illuminants may be characterized by their spectral power distribution (SPD). The relative SPD curves provided by many manufacturers may have been produced using 10 nm increments or more on their spectroradiometer.[33] The result is what would seem to be a smoother ("fuller spectrum") power distribution than the lamp actually has. Owing to their spiky distribution, much finer increments are advisable for taking measurements of fluorescent lights, and this requires more expensive equipment. Approximation Color rendering index Spectral power distribution 21 of 25 January 15, 2019, Item # 3.2 In astronomy, the color temperature is defined by the local slope of the SPD at a given wavelength, or, in practice, a wavelength range. Given, for example, the color magnitudes B and V which are calibrated to be equal for an A0V star (e.g. Vega), the stellar color temperature is given by the temperature for which the color index of a black-body radiator fits the stellar one. Besides the , other color indices can be used as well. The color temperature (as well as the correlated color temperature defined above) may differ largely from the effective temperature given by the radiative flux of the stellar surface. For example, the color temperature of an A0V star is about 15000 K compared to an effective temperature of about 9500 K.[34] Kruithof curve Luminous efficacy Over-illumination Brightness temperature Effective temperature Whiteness Color metamerism 1. See the comments section of this LightNowBlog.com article (http://www.lightnowblog.com/2016/07/ama-issues-led-st reetlighting-guidance-controversy-ensues/) Archived (https://web.archive.org/web/20170307123725/http://www.lightn owblog.com/2016/07/ama-issues-led-streetlighting-guidance-controversy-ensues/) 2017-03-07 at the Wayback Machine. on the recommendations of the American Medical Association to prefer LED-lighting with cooler color temperatures (i.e. warmer color). 2. "OSRAM SYVLANIA XBO" (https://web.archive.org/web/20160303212115/http://assets.sylvania.com/assets/docume nts/ENGR_BLTN11.161355cc-1d94-4996-b6cd-a3001fea6f1a.pdf) (PDF). Archived from the original (http://assets.sy lvania.com/assets/documents/ENGR_BLTN11.161355cc-1d94-4996-b6cd-a3001fea6f1a.pdf) (PDF) on 2016-03-03. 3. Wallace Roberts Stevens (1951). Principles of Lighting (https://books.google.com/?id=gH5RAAAAMAAJ&q=micro-re ciprocal-degree+date:0-1960&dq=micro-reciprocal-degree+date:0-1960). Constable. 4. Williams, D. R. (2004). "Sun Fact Sheet" (http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html). NASA. Archived (https://web.archive.org/web/20131206053849/http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html) from the original on 2013-12-08. Retrieved 2010-09-27. 5. "Principles of Remote Sensing — CRISP" (http://www.crisp.nus.edu.sg/~research/tutorial/optical.htm). Archived (http s://web.archive.org/web/20120702174159/http://www.crisp.nus.edu.sg/~research/tutorial/optical.htm) from the original on 2012-07-02. Retrieved 2012-06-18. 6. Chris George (2008). Mastering Digital Flash Photography: The Complete Reference Guide (https://books.google.co m/?id=j728wJySfyQC&dq=blue+cool+red+hot+color-temperature+sun). Sterling Publishing Company. p. 11. ISBN 978-1-60059-209-6. Characteristic spectral power distributions (SPDs) for an incandescent lamp (left) and a fluorescent lamp (right). The horizontal axes are wavelengths in nanometers, and the vertical axes show relative intensity in arbitrary units. Color temperature in astronomy Characteristic spectral power distribution of an A0V star (Teff = 9500 K, cf. Vega) compared to black- body spectra. The 15000 K black-body spectrum (dashed line) matches the visible part of the stellar SPD much better than the black body of 9500 K. All spectra are normalized to intersect at 555 nanometers. See also References 22 of 25 January 15, 2019, Item # 3.2 7. Rüdiger Paschotta (2008). Encyclopedia of Laser Physics and Technology (https://books.google.com/?id=BN026ye2 fJAC&pg=PA219&dq=lighting+color-temperature+relaxing&q=lighting%20color-temperature%20relaxing). Wiley- VCH. p. 219. ISBN 978-3-527-40828-3. 8. Thomas Nimz, Fredrik Hailer and Kevin Jensen (2012). Sensors and Feedback Control of Multi-Color LED Systems (https://web.archive.org/web/20140429162806/http://www.mazet.de/en/english-documents/english/featured-articles/s ensors-and-feedback-control-of-multi-color-led-systems-1/download#.UX7VXYIcUZI). LED Professional. pp. 2–5. ISSN 1993-890X (https://www.worldcat.org/issn/1993-890X). Archived from the original (http://www.mazet.de/en/engl ish-documents/english/featured-articles/sensors-and-feedback-control-of-multi-color-led-systems-1/download#.UX7V XYIcUZI) on 2014-04-29. 9. Chaplin, Martin. "Water Absorption Spectrum" (http://www.lsbu.ac.uk/water/vibrat.html). Archived (https://web.archiv e.org/web/20120717061228/http://www.lsbu.ac.uk/water/vibrat.html) from the original on 2012-07-17. Retrieved 2012-08-01. 10. Pope R. M., Fry E. S. (1997). "Absorption spectrum (380–700 nm) of pure water. II. Integrating cavity measurements" (http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-36-33-8710). Applied Optics. Optical Society of America. 36 (33): 8710–8723. doi:10.1364/AO.36.008710 (https://doi.org/10.1364%2FAO.36.008710). Archived (h ttps://web.archive.org/web/20141114195506/http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-36-33-8710) from the original on November 14, 2014. Retrieved August 1, 2012. 11. Jerlov N. G. (1976). Marine Optics (https://books.google.com/books?id=tzwgrtnW_lYC&lpg=PA128&pg=PA128#v=o nepage&q&f=false). Elsevie Oceanography Series. 14. Amsterdam: Elsevier Scientific Publishing Company. pp. 128–129. ISBN 0-444-41490-8. Archived (https://web.archive.org/web/20171221064443/https://books.google.co m/books?id=tzwgrtnW_lYC&lpg=PA128&pg=PA128#v=onepage&q&f=false) from the original on December 21, 2017. Retrieved August 1, 2012. 12. Kern, Chris. "Reality Check: Ambiguity and Ambivalence in Digital Color Photography" (http://www.chriskern.net/ess ay/realityCheck.html). Archived (https://web.archive.org/web/20110722001411/http://www.chriskern.net/essay/reality Check.html) from the original on 2011-07-22. Retrieved 2011-03-11. 13. Borbély, Ákos; Sámson, Árpád; Schanda, János (December 2001). "The concept of correlated colour temperature revisited" (https://web.archive.org/web/20090205040121/http://www.knt.vein.hu/staff/schandaj/SJCV-Publ-2005/462. doc). Color Research & Application. 26 (6): 450–457. doi:10.1002/col.1065 (https://doi.org/10.1002%2Fcol.1065). Archived from the original (http://www.knt.vein.hu/staff/schandaj/SJCV-Publ-2005/462.doc) on 2009-02-05. 14. Hyde, Edward P. (June 1911). "A New Determination of the Selective Radiation from Tantalum (abstract)". Physical Review. Series I. The American Physical Society. 32 (6): 632–633. doi:10.1103/PhysRevSeriesI.32.632 (https://doi.o rg/10.1103%2FPhysRevSeriesI.32.632). "This existence of a color match is a consequence of there being approximately the same energy distribution in the visible spectra." 15. Priest, Irwin G. (1923). "The colorimetry and photometry of daylight ·and incandescent illuminants by the method of rotatory dispersion" (http://www.opticsinfobase.org/abstract.cfm?URI=josa-7-12-1175). JOSA. 7 (12): 1175–1209. doi:10.1364/JOSA.7.001175 (https://doi.org/10.1364%2FJOSA.7.001175). "The color temperature of a source is the temperature at which a Planckian radiator would emit radiant energy competent to evoke a color of the same quality as that evoked by the radiant energy from the source in question. The color temperature is not necessarily the same as the 'true temperature' of the source; but this circumstance has no significance whatever in the use of the color temperature as a means to the end of establishing a scale for the quality of the color of illuminants. For this purpose no knowledge of the temperature of the source nor indeed of its emissive properties is required. All that is involved in giving the color temperature of any illuminant is the affirmation that the color of the luminant is of the same quality as the color of a Planckian radiator at the given temperature." 16. Davis, Raymond (1931). "A Correlated Color Temperature for Illuminants". National Bureau of Standards Journal of Research. 7: 659–681. doi:10.6028/jres.007.039 (https://doi.org/10.6028%2Fjres.007.039). "The ideal correlated colour temperature of a light source is the absolute temperature at which the Planckian radiator emits radiant energy component to evoke a colour which, of all Planckian colours, most closely approximates the colour evoked by the source in question." from Research Paper 365 17. Judd, Deane B. (1931). "Chromaticity sensibility to stimulus differences" (http://www.opticsinfobase.org/abstract.cfm? id=48631). JOSA. 22 (2): 72–108. doi:10.1364/JOSA.22.000072 (https://doi.org/10.1364%2FJOSA.22.000072). 18. Priest, Irwin G. (February 1933). "A proposed scale for use in specifying the chromaticity of incandescent illuminants and various phases of daylight" (http://www.opticsinfobase.org/abstract.cfm?URI=josa-23-2-41). JOSA. 23 (2): 42. doi:10.1364/JOSA.23.000041 (https://doi.org/10.1364%2FJOSA.23.000041). 23 of 25 January 15, 2019, Item # 3.2 19. Judd, Deane B. (January 1933). "Sensibility to Color-Temperature Change as a Function of Temperature" (http://ww w.opticsinfobase.org/abstract.cfm?URI=josa-23-1-7). JOSA. 23 (1): 7. doi:10.1364/JOSA.23.000007 (https://doi.org/ 10.1364%2FJOSA.23.000007). "Regarding (Davis, 1931): This simpler statement of the spectral-centroid relation might have been deduced by combining two previous findings, one by Gibson (see footnote 10, p. 12) concerning a spectral-centroid relation between incident and transmitted light for daylight filters, the other by Langmuir and Orange (Trans. A.I.E.E., 32, 1944–1946 (1913)) concerning a similar relation involving reciprocal temperature. The mathematical analysis on which this latter finding is based was given later by Foote, Mohler and Fairchild, J. Wash. Acad. Sci. 7, 545–549 (1917), and Gage, Trans. I.E.S. 16, 428–429 (1921) also called attention to this relation." 20. Judd, Deane B. (January 1935). "A Maxwell Triangle Yielding Uniform Chromaticity Scales" (http://www.opticsinfobas e.org/abstract.cfm?URI=josa-25-1-24). JOSA. 25 (1): 24–35. doi:10.1364/JOSA.25.000024 (https://doi.org/10.1364% 2FJOSA.25.000024). "An important application of this coordinate system is its use in finding from any series of colors the one most resembling a neighboring color of the same brilliance, for example, the finding of the nearest color temperature for a neighboring non-Planckian stimulus. The method is to draw the shortest line from the point representing the non-Planckian stimulus to the Planckian locus." 21. OSA Committee on Colorimetry (November 1944). "Quantitative data and methods for colorimetry" (http://www.optic sinfobase.org/abstract.cfm?URI=josa-34-11-633). JOSA. 34 (11): 633–688. (recommended reading) 22. Judd, Deane B. (November 1936). "Estimation of Chromaticity Differences and Nearest Color Temperatures on the Standard 1931 I.C.I. Colorimetric Coordinate System" (http://www.opticsinfobase.org/abstract.cfm?URI=josa-26-11-4 21). JOSA. 26 (11): 421–426. doi:10.1364/JOSA.26.000421 (https://doi.org/10.1364%2FJOSA.26.000421). 23. MacAdam, David L. (August 1937). "Projective transformations of I.C.I. color specifications" (http://www.opticsinfoba se.org/abstract.cfm?URI=josa-27-8-294). JOSA. 27 (8): 294–299. doi:10.1364/JOSA.27.000294 (https://doi.org/10.1 364%2FJOSA.27.000294). 24. The CIE definition of correlated color temperature (removed) (http://www.delta.dk/C1256ED600446B80/sysOakFil/i1 02/$File/I102%20Correlated%20Colour%20Temperature.pdf) Archived (https://web.archive.org/web/2009020504012 2/http://www.delta.dk/C1256ED600446B80/sysOakFil/i102/%24File/I102%20Correlated%20Colour%20Temperature. pdf) 2009-02-05 at the Wayback Machine. 25. Schanda, János; Danyi, M. (1977). "Correlated Color-Temperature Calculations in the CIE 1976 Chromaticity Diagram". Color Research & Application. Wiley Interscience. 2 (4): 161–163. doi:10.1002/col.5080020403 (https://do i.org/10.1002%2Fcol.5080020403). "Correlated color temperature can be calculated using the new diagram, leading to somewhat different results than those calculated according to the CIE 1960 uv diagram." 26. Kelly, Kenneth L. (August 1963). "Lines of Constant Correlated Color Temperature Based on MacAdam's (u,v) Uniform Chromaticity Transformation of the CIE Diagram" (http://www.opticsinfobase.org/abstract.cfm?URI=josa-53- 8-999). JOSA. 53 (8): 999–1002. doi:10.1364/JOSA.53.000999 (https://doi.org/10.1364%2FJOSA.53.000999). 27. Robertson, Alan R. (November 1968). "Computation of Correlated Color Temperature and Distribution Temperature" (http://www.opticsinfobase.org/abstract.cfm?URI=josa-58-11-1528). JOSA. 58 (11): 1528–1535. doi:10.1364/JOSA.58.001528 (https://doi.org/10.1364%2FJOSA.58.001528). 28. ANSI C implementation (http://www.brucelindbloom.com/index.html?Eqn_XYZ_to_T.html) Archived (https://web.archi ve.org/web/20080422034438/http://www.brucelindbloom.com/index.html?Eqn_XYZ_to_T.html) 2008-04-22 at the Wayback Machine., Bruce Lindbloom 29. Walter, Wolfgang (February 1992). "Determination of correlated color temperature based on a color-appearance model". Color Research & Application. 17 (1): 24–30. doi:10.1002/col.5080170107 (https://doi.org/10.1002%2Fcol.5 080170107). "The concept of correlated color temperature is only useful for lamps with chromaticity points close to the black body…" 30. Schanda, János (2007). "3: CIE Colorimetry". Colorimetry: Understanding the CIE System. Wiley Interscience. pp. 37–46. doi:10.1002/9780470175637.ch3 (https://doi.org/10.1002%2F9780470175637.ch3). ISBN 978-0-470- 04904-4. 31. McCamy, Calvin S. (April 1992). "Correlated color temperature as an explicit function of chromaticity coordinates". Color Research & Application. 17 (2): 142–144. doi:10.1002/col.5080170211 (https://doi.org/10.1002%2Fcol.508017 0211). plus erratum doi:10.1002/col.5080180222 (https://doi.org/10.1002%2Fcol.5080180222) 32. Hernández-Andrés, Javier; Lee, RL; Romero, J (September 20, 1999). "Calculating Correlated Color Temperatures Across the Entire Gamut of Daylight and Skylight Chromaticities" (http://www.usna.edu/Users/oceano/raylee/papers/ RLee_AO_CCTpaper.pdf) (PDF). Applied Optics. 38 (27): 5703–5709. doi:10.1364/AO.38.005703 (https://doi.org/10. 1364%2FAO.38.005703). PMID 18324081 (https://www.ncbi.nlm.nih.gov/pubmed/18324081). Archived (https://web. archive.org/web/20160401133754/http://www.usna.edu/Users/oceano/raylee/papers/RLee_AO_CCTpaper.pdf) (PDF) from the original on April 1, 2016.24 of 25 January 15, 2019, Item # 3.2 Stroebel, Leslie; John Compton; Ira Current; Richard Zakia (2000). Basic Photographic Materials and Processes (2E ed.). Boston: Focal Press. ISBN 0-240-80405-8. Wyszecki, Günter; Stiles, Walter Stanley (1982). "3.11: Distribution Temperature, Color Temperature, and Correlated Color Temperature". Color Science: Concept and Methods, Quantitative Data and Formulæ. New York: Wiley. pp. 224–229. ISBN 0-471-02106-7. Kelvin to RGB calculator from Academo.org Boyd, Andrew. Kelvin temperature in photography at The Discerning Photographer. Charity, Mitchell. What color is a black body? sRGB values corresponding to blackbodies of varying temperature. Lindbloom, Bruce. ANSI C implementation of Robertson's method to calculate the correlated color temperature of a color in XYZ. Konica Minolta Sensing. The Language of Light. Retrieved from "https://en.wikipedia.org/w/index.php?title=Color_temperature&oldid=869591767" This page was last edited on 19 November 2018, at 16:08 (UTC). Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. 33. Gretag's SpectroLino (http://www.xrite.com/documents/literature/gmb/en/200_spectrolino_manual_en.pdf) Archived (https://web.archive.org/web/20061110131804/http://www.xrite.com/documents/literature/gmb/en/200_spectrolino_m anual_en.pdf) 2006-11-10 at the Wayback Machine. and X-Rite's ColorMunki (http://www.pictureline.com/images/pd f/L11-246%20CM%20CompetitCompr_03-17-08.pdf) Archived (https://web.archive.org/web/20090205040118/http:// www.pictureline.com/images/pdf/L11-246%20CM%20CompetitCompr_03-17-08.pdf) 2009-02-05 at the Wayback Machine. have an optical resolution of 10 nm. 34. Unsöld, Albrecht; Bodo Baschek (1999). Der neue Kosmos (6 ed.). Berlin, Heidelberg, New York: Springer. ISBN 3- 540-64165-3. Further reading External links 25 of 25 January 15, 2019, Item # 3.2