Цветовая температура светодиодных ламп освещения

Цветовая температура светодиодных ламп — один из наиболее важных параметров, относящихся к осветительному оборудованию. Данный параметр следует принимать во внимание не только при решении интерьерных задач, но и при подборе автомобильных ламп. Цветовая температура — комплексное понятие, которое включает в себя такие характеристики, как спектральные свойства, цвет свечения, индекс цветовой передачи и много другое.

Физическая трактовка цветовой температуры

Впервые проблема цветовой температуры упомянута в работах великого физика Макса Планка. В его трудах по квантовой физике затрагивались законы распределения энергии, в результате чего было обособлено значение цветовой температуры. В качестве единицы измерения этого состояния (как и в случае абсолютной температуры) выбраны кельвины. Формула определяет этот показатель как равный температуре абсолютного черного тела, при которой тело производит излучение в цветовом диапазоне, равном измеряемому.

В люминесцентных лампах цветовая температура замеряется методом их сравнения с абсолютно черным телом. Отображается полученный показатель в виде линии черного тела. За абсолютно черное тело принимается всякий твердый объект, обладающий некоторыми свойствами. При этом объект находится в раскаленном состоянии. Когда меняются показатели, происходит смена и спектральных параметров. К примеру, когда на шкале Кельвина пересекается определенная метка, происходит рост синей части и падение красной. Если же температура падает, происходят обратные изменения.

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Корреляция цветовой температуры

Когда температура абсолютно черного тела повышается, начинается процесс накаливания. Образно накаливание можно сопоставить с нагревом металла. Происходит смена цветов в определенном порядке: красный, оранжевый, желтый, белый, голубой. В цветовом пространстве процесс накаливания отображается на соответствующей кривой.

Для ламп накаливания цветовая температура примерно равна 2700 кельвинам. Излучение находится в теплой или красной области оттенков. При этом температура нити лампочки накаливании точно расположена на 2700 К.

Благодаря использованию спектрального анализа видимой части спектра, можно определить данные по другим типам источников света. К примеру, температура светодиодов не показывает степени их разогрева: на отметке 2700 К светодиод нагревается лишь до 80 градусов по Цельсию.

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Восприятие цветов

Цветовосприятие каждого человека индивидуально. Восприятие каждого цвета — это некий компромиссный результат, полученный на основе обработки сигнала, принятого зрительными нервами. Воспринимаемые оттенки могут значительно отличаться от человека к человеку.

Также следует принимать во внимание и тот факт, что с возрастом происходит искажение цветовосприятия. В частности хрусталик приобретает желтоватый цвет, что вносит коррективы в восприятие приходящей от зрительных нервов информации. Также немалую роль в цветовосприятии имеет фактор психологии.

Общепризнанно, что человеческий глаз может отличать до 10 миллионов оттенков. Причем более четырех сотен из них относятся к разновидностям ахроматического серого цвета. Однако такое количество воспринимаемых оттенков не должно вводить в заблуждение: к примеру, солнечный луч легко искажает цветовосприятие.

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Световые цвета

Определение холодного объекта без излучения не создает каких-либо сложностей. Одним из главных отражательных параметров такого объекта является длина волны или обратная ей характеристика — частота. Если же речь идет о разогретом излучающем теле, то дела обстоят по-другому.

Абсолютно черное тело не отражает световые лучи. В качестве примера можно привести спираль из вольфрама в стандартной электрической лампе. Разберемся, как соединяется такая лампочка через реостат с электрической цепочкой.

Ниже представлена последовательность наблюдений:

1. Свет включен, электричество передается на клеммы.
2. Уровень сопротивления медленно снижается.
3. Абсолютно черное тело начинает слегка светиться красным.

Если в этот момент проверить температуру объекта, она будет находиться на уровне 900 градусов выше нуля. Согласно закону о сверхпроводимости, при нулевой температуре по Кельвину скорость атомов также будет равна нулю. Однако именно от скорости и зависит излучение.

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Цветовая температура и оттенки

Для начала видимого спектра излучения абсолютно черного тела характерен уровень в 1200 кельвинов. Этот уровень граничит с красным оттенком. Если накаливать спираль и дальше, произойдут значительные цветовые изменения. При 2000 К вместо красного цвета появится ярко-оранжевый, со временем переходящий в желтый. Полное доминирование желтого наступит при 3000 К.

Для спиралей из вольфрама пиком является уровень в 3500 Кельвинов. Далее спирали подвергаются плавлению. Однако источники света других типов можно нагревать и до больших температур. К примеру, светодиоды без проблем разогреваются до 5500 К или даже более высоких температур. На 5500 К светодиоды покажут ярко-белый цвет, на 6000 К — голубоватый, а на 18000 К — фиолетовый.

Цветовая температура оказывает непосредственное влияние на восприятие оттенков. Характеристики холодной и теплой гаммы значительно разнятся. К примеру, температура свечки — 1200 К, а температурный показатель неба в зимнее время года может доходить до 12000 К.

Цветовая температура	Оттенок	Характеристика
2700К	Теплый белый, красновато-белый	Используется в обычных лампах накалывания. Делает интерьер более уютным, по настоящему домашним
3000К	Теплый белый, желто-белый	Является характерным для большенства галогеновых ламп, несколько холоднее, чем свет от лампы накалывания
3500К	Обычный белый	Таким является излучение от флюорисцентных трубок различных размеров
4000К	Холодный белый	Является незаменимым атрибудом стиля хай-тэк, но своей стерильностью ассоциируется с больницей
5000-6000К	Дневной	Используется для имитации дневного света в оранжереях и террариумах
6500К	Холодный дневной	Используется при профессиональной фотосьемке и в кинематографе

Выбор осветительных приборов нужно делать исходя из поставленных задач. При поиске соответствующего эффекта следует учитывать, что температура и интенсивность свечения могут восприниматься не одинаково в разное время суток.

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Светодиодное освещение

Освещение на диодах — один из наиболее распространенных типов осветительных приборов. Цветовая температура диодов характеризуется тремя основными оттенками:

1. Белый в теплой гамме (за рубежом обозначается как Warm White) — до 3300 К.
2. Натуральный белый (Neutral White) — до 5000 К.
3. Белый в холодной гамме (Cool White) — более 5000 К.

Температурные особенности светодиодов в значительной степени определяют сферы их применения. Прежде всего, диоды используются в уличном освещении, на рекламных билбордах, а также в автомобильной светотехнике.

Обратите внимание! Цветовая температура диодов позволяет не только установить контрастность, но и дает возможность определиться с тем, как будет восприниматься свет при смене погоды.

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Белый свет в холодной гамме

Самой большой точностью восприятия отличается солнечное освещение. Для прочих же источников света характерны значительно более низкие показатели. К примеру, для большинства светодиодных светильников показатель температуры находится в границах 5000-8000 Кельвинов. Средний показатель передачи по соответствующему индексу не превышает 65 единиц.

К достоинствам источников света в холодной цветовой гамме относится их высокая контрастность, что очень хорошо при освещении затемненных предметов. Светодиоды, благодаря возможности функционирования на больших расстояниях, — лучший выбор для освещения дорожного покрытия.

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Нейтральный и теплый свет

Следует учитывать, что холодные оттенки в наибольшей степени искажают восприятие цветов. Для холодного цвета характерна резкость, благодаря чему достигается контрастность, однако для человеческого глаза это вредно.

Теплая гамма менее раздражающе действует на зрение. В диапазоне 2500-6000 К индекс цветопередачи повышается до 75-80 единиц, и подобные осветительные приборы показывают отличные результаты на незначительных расстояниях. Теплые и нейтральные тона демонстрируют явное преимущество при освещении в плохую погоду. К примеру, атмосферные осадки оказывают существенное влияние на качество холодного света, тогда как для теплых оттенков дождь или снег несущественны. Причина в том, что теплые источники позволяют рассмотреть не только сам объект, но и пространство возле него. Кстати говоря, по той же причине теплая гамма более эффективна под водой.

Обратите внимание! Для энергосберегающих лампочек характерен теплый спектр. Это хорошо, так как для освещения жилых помещений малопригодна холодная гамма.

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Ксеноновое освещение

Особенности ксеноновых и биксеноновых ламп диктуются не только компаниями-производителями, но и техническими нюансами, находящимися в тесной зависимости от цветовой температуры:

1. Ярко-желтый цвет (3000 кельвинов) чаще всего используется в противотуманных фарах. Уровень светового потока приблизительно равен 3300 люмен.
2. Бело-желтый (4300 К). Используется в противотуманном и головном освещении. Характеризуется повышенной цветоотдачей (3300-3500 люмен). Не перенапрягает зрительные нервы, хорошо заметен на сыром асфальте. Важная особенность — не угнетает зрение водителям попутных автомобилей.
3. Стандартный белый (4500-5000 К). Подобный уровень цветовой температуры наилучшим образом воспринимается глазом человека. Характеризуется значительной цветоотдачей (примерно 3000 люмен), что позволяет использовать лампы со стандартным белым цветом для решения широкого диапазона задач.
4. Белый холодного спектра и бело-голубой (свыше 6000 К). Степень голубизны в цвете варьируется в зависимости от разновидности оптической техники (линзы или рефлекторов). Осветительные приборы этого типа показывают худшие результаты в сырую погоду, но на сухом асфальте и на снегу по видимости им нет равных.
5. Синий, фиолетово-синий (более 8000 К). Источники света с такими температурными показателями относятся к декоративным. Им свойственна невысокая излучающая способность (не более 2200 люмен), а потому утилитарное применение им найти сложно.

Обратите внимание! Согласно выводам европейских исследователей, большинство автовладельцев отдают предпочтение ксеноновым фарам с цветовой температурой на уровне 6000 К.

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Заключение

Все характеристики освещения следует рассматривать в единстве. Цветовая температура связана с яркостью, контрастностью, что непосредственно сказывается на комфортности восприятия того или иного источника света. При этом для решения одних задач правильнее выбрать освещение в холодном спектре, для других же случаев оптимальным решением будет теплая цветовая гамма.

Цветовая температура светодиодных ламп освещения

90000 The Physics of Light and Color 90001 90002 The color temperature model is based on the relationship between the temperature of a theoretical standardized material, called a 90003 90004 black body radiator 90005 90006, and the energy distribution of its emitted light as the radiator is brought to increasingly higher temperatures, measured in Kelvin (K). Although this radiator does not exist, many metals behave very similar to a black body so we can take a metal pot as an example for this discussion.90007 90002 In our example, illustrated in Figure 1 above, the metal pot is first heated to a temperature of about 900 K (pot on the left), where it begins to glow a dull red. As the temperature is increased to between 1500 and 2000 K, the pot (second to the left) turns a yellowish to brighter red color. As the temperature is further increased above 3000 K the color turns to a yellow-white (the third pot from the left), and at 5000 K and above (the pot on the far right), a bluish-white color appears.The figure above can be further investigated in our 90003 interactive Java-powered Color Temperature Tutorial 90006. 90007 90012 Color Temperature 90013 90002 Explore how color temperature is affected by changes in the temperature of a black body radiator. 90007 90002 The absolute temperature of the black body radiator is expressed in degrees Kelvin, which is equivalent to degrees Centigrade (° C) plus 273 degrees. For example 1000 K equals 727 ° C. Therefore, we can define the color temperature of a light source as the value of the absolute temperature of a black body radiator when the radiator chromaticity matches that of the light source.In the case of fluorescent lamps that can only approximate the chromaticity of a black body, the corrected term «correlated» color temperature is applied through a calculated chromaticity. 90007 90002 The color temperature chart below (Figure 2) illustrates the range of colors generated by both inside (artificial) and outside (natural sunlight) lighting. Values ​​falling below 3500 K are generally considered to be in the «tungsten» range and neutral colors viewed under this illumination often appear more red that they do under natural daylight.90007 90002 The concept of color temperature is very important in the photography arena, where film emulsions must be balanced to accurately render color using different light sources. For instance, films intended to be used outside in ordinary daylight, fluorescent, and flash lighting are balanced during manufacture for a color temperature of 5500 K while films made for indoor tungsten light bulb use are balanced for a color temperature of 3200 to 3400 K. The 5500 K average daylight color spectrum varies during different parts of the day.In the early morning and late evening, the color temperature will fall to 5000 K and lower causing color shifts in the emulsion resulting in warmer (redder) color rendering. 90007 90002 Most light bulbs that are used for indoor illumination have some form of tungsten filament (with the exception of fluorescent bulbs). These bulbs emit a wavelength spectrum centered in the 3200 K color temperature region and films color balanced for this type of illumination will produce the best results. Using daylight balanced films under tungsten illumination will shift all color tones towards a decidedly yellow cast.Likewise, using tungsten balanced films under daylight illumination will shift color tones towards a bluer cast. All major film manufacturers have one or several 3200 K films available in 35 mm transparency format. Transparency film is preferable to color negative film for several reasons. First, all color negative films are color balanced for 5500 K and must be manipulated during printing to avoid the yellow cast mentioned above. Most photo processors can not or will not produce satisfactory results with photomicrographs on color negative film.Also, the contrast and color saturation in transparency film can not be equaled by color negative film. 90007 90002 The clown photographs in Figure 3 above illustrate the proper use of color balance between film emulsions and illumination sources. The clown in the center (Figure 3 (b)) was photographed under natural sunlight using daylight-balanced (5000 K) Fujichrome Velvia. Using the same film, the clown on the left (Figure 3 (a)) was photographed indoors under tungsten illumination. Note that all hues are shifted to lower wavelengths and the overall image has a definite yellow cast.The clown on the right (Figure 3 (c)) was photographed under natural sunlight, but this time the film was tungsten-balanced (3200 K) Fujichrome 64T. Under these conditions, the image has an overall blue cast and appears very unnatural. By carefully coordinating lighting conditions with film emulsion, most photographers can easily take beautiful images that accurately reproduce the actual colors of the subject. 90007 90002 90003 Color Temperature 90006 — For a more detailed treatment of color temperature visit the corresponding article in our section on photomicrography.90007 90012 Contributing Authors 90013 90002 90003 Mortimer Abramowitz 90006 — Olympus America, Inc., Two Corporate Center Drive., Melville, New York, 11747. 90007 90002 90003 Michael W. Davidson 90006 — National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr ., The Florida State University, Tallahassee, Florida, 32310. 90007.90000 Three-Point Lighting and Color Temperature Basics 90001 90002 Ready to light your first shot? Learn how to set up a basic three-point lighting arrangement, and discover how the kelvin scale will affect the color temperature of your footage. 90003 90004 Open any book on the practices of filmmaking, and it’s a sure bet that within the first dozen pages, you’ll find a sentence that starts, «With good lighting, any scene …» But what is «good lighting» and how can you achieve it as a beginner? The best place to start is with a three-point lighting setup.90005 90004 Lighting a scene has an infinite amount of variations and arrangements, but a three-point setup is all you need in the beginning. In this article, we’ll break down the measurement of color temperature on the Kelvin scale and look at the process of setting up a basic three-point lighting kit. This is all the info you need to properly light a shot. 90005 90008 90009 Three-Point Lighting 90010 90004 Three-point lighting, of course, is derived from three lighting sources: the key light, the fill light, and the back light.Let’s take a look. 90005 90009 90014 1. The Key Light 90015 90010 90004 The key light will be the primary light source of the scene. The term «key light» is not derived from a specific type of light or intensity; it’s merely the main light that illuminates your subject. The light could be a Fresnel fixture, or it could be the sunlight coming through the window. However, in this guide, we’re going to look at the key light as a lighting fixture, not as available light. 90005 90004 Since the key light will set the look of your scene, it’s the first light you’ll want to assemble and place.Conventionally, the key light is placed 45 ° to the side of the actor or subject, and 45 ° above. That placement is just a rule of thumb — you can technically place the key light beneath the subject if that fits the tone and direction of the scene. 90005 90021 90004 There are numerous permutations for a lighting setup, and for some circumstances, a sole key light may be enough. Following the conventional 45 degree setup, the light source on the opposite side of the eyeline to the camera. cheek patch which forms on the cheek opposite from the light.With this you can achieve «Rembrandt lighting,» will throw the shadow of the nose across the cheek, leaving a light patch (upside-down triangle) on the cheek. Many cinematographers and photographers prefer this type of lighting. 90005 90004 90025 90026 90005 90004 90014 Key Light Variables 90015 90005 90004 Of course, there are two sides on which you can light the actor. Customarily you will get more photographic results by lighting the actor with a far-side key. What does this mean? Typically in standard coverage, the actor looks either to the left or right of the camera, which is called camera left or camera right.In doing so, you will see one side of their face more prominently than the other. The side of the face that you can clearly see is called the near side, and the far side is, of course, the opposite side of the face that you can not see as clearly. When lighting for the far side, the key light will push the shadows of the face across onto the near side, creating more contrast and depth to the face 90005 90034 90004 If you place the key on the near side, the light will appear less pleasing. Of course, there is no right or wrong placement, and sometimes the scene may call for a near side key.90005 90037 90004 Sometimes, however, the key light creates too much heavy contrast and will require a fill light to decrease the contrast ratio. 90005 90009 90014 2. Fill Light 90015 90010 90004 As the name suggests, this light is used to fill in shadowy areas of the face / subject that were created by the key light. Typically you’ll want to use a fill light that is softer and less intense than the key. The goal is to raise part of the face out of the shadows without creating any additional shadows.90005 90004 As Todd explains in the following Shutterstock tutorial, practicals make for great fill lights. 90005 90004 90049 90026 90005 90004 If you were to use a fill light at the same intensity as the key, your shot might look like the following. Both sides are brightly illuminated, and shadows are being cast from either side of the face. To some extent, it seems like the actor is being illuminated by the flash from a camera. 90005 90054 90004 90014 Negative Fill 90015 90005 90004 The amount of fill will dictate the contrast ratio, which will ultimately dictate the mood and tone of the shot.Sometimes you may not want any fill; instead you want the contrast to remain or even increase. However, due to the directionality of the key light the subject may receive light bounced back from an adjacent surface, such as a wall. This ambient light will softly illuminate the face. You can negate this light by using negative fill. 90005 90061 90004 Negative fill is a form of reductive lighting, which means it takes away light. You can create contrast by adding a black flag / frame / floppy of some kind that absorbs light instead of reflecting it.90005 90009 90014 3. Back Light 90015 90010 90004 The back light, also known as the rim light, is a light that hits the back of the head and shoulders to make the subject stand out from the background. Typically a backlight would be used in darker scenes where the subject would otherwise merge into the dark background. As seen in the still below from Game of Thrones, Jamie is illuminated by a light acting as the fire, but because they are in a dark dungeon, there’s not much other light to be sourced.Without the moonlight coming in from the window, Jamie would be indistinguishable from the dark background, as we can see, his right shoulder has already started to do so. 90005 90070 90008 90009 Using Three-Point Lighting in Filmmaking 90010 90004 While three-point lighting is a fundamental lighting setup for pleasing imagery, it’s not necessarily fitting or practical for all scenes. Three-point lighting produces a clean, by-the-books shot which might not match the intended tone for the scene.There are many critics online that argue that three-point lighting is only ideal for interviews and broadcast. Regardless, this lighting arrangement teaches you the fundamentals of lighting a subject. Your scene always needs a key, and if the scene is dark you know the subject needs a backlight, and if there’s too much contrast? You add a fill light. You can see three-point lighting executed perfectly for an interview in Shutterstock Tutorial’s video on lighting interviews below. 90005 90004 90077 90026 90005 90004 There are numerous lighting arrangements you can add to three-point lighting: a sidelight, hair light, eye light and so on.These can be added to a three-point setup, or positioned in lieu of one of the three point lights. For example, move the key from 45 ° to 90 °, and you have a sidelight (although it’s technically still your key as it’s your primary light source). 90005 90004 This was my shot without any lighting; the actor is only illuminated by the soft sunlight diffused through the window blinds and the ambient light in the background. Before I light, I have to consider the tone of the scene: The character has just returned home from a court hearing where he has not received the verdict he wanted.90005 90084 90004 To capture this I used a single key light with negative fill positioned to the right of the actor. It creates a stark contrast that clues the viewer into the drama of the moment. Since there’s ambient light in the background that creates depth between the character and wall / window, there was no need for a rim light.If I was to light this scene following the three-point setup directly, it would not have worked. 90005 90087 90004 90089 Check out more lighting arrangements.90090 90005 90008 90009 Color Temperature 90010 90004 With the increase in consumer-priced LEDs, more people are leaving tungsten-based Fresnel’s in the past and opting for cheaper, brighter, and more energy-saving alternatives. However, there’s one big difference between the two formats — the color temperature. 90005 90097 The Kelvin Scale 90098 90004 The color of light is measured along a Kelvin scale, from 1000k to 10,000k. This quote from Harry C. Box from the 90089 Set Lighting Technician’s Handbook 90090 perfectly summarizes the methodology.90005 90103 90004 You may be wondering why the Kelvin scale (a temperature scale) is used to quantify color balance. In order to give us a fixed reference point, scientists decided to compare the color makeup of any source to that of a theoretical «perfect black body radiator» when it is heated. The idea is that light is emitted when a substance is heated. How much it is heated determines the color makeup of the light. When heated a little, it glows red. Heated more it becomes orange, then yellow, and then gradually less yellow and more pale blue, and finally brilliant blue.90005 90106 90004 To summarize even further, color with a lower kelvin appears more red, while a higher number represents a more blue look. The temperature scale begins around the 1000K range, which you can equate to the look of a candle flame or match fire. This is actually an easy way to remember the Kelvin scale — the lower numbers are related to fire, which is red and orange. 90005 90109 90089 Image via Sompoch Tangthai 90090 90004 With that, you can see how the Kelvin scale correlates to specific lighting equipment.Tungsten based lights, like an Arri 650 Fresnel, would typically have a temperature that sits around 3200k. You can obtain LEDs with a temperature of 3200k, but for the most part they are daylight balanced. Daylight fluctuates between 5500k-5700k and will decrease to as low as 2000k-2500k at dusk and dawn, or increase as high as 7000k on an overcast day. 90005 90097 Balancing Color Temperature 90098 90004 In my example shot, the ambient light through the rear windows and the blinds at the front is daylight balanced (it’s daylight after all), and the tungsten fresnels I used are 3200k.90005 90004 To balance this, I had to apply a correction gel. They come in two forms: CTO and CTB, or color temperature orange and color temperature blue. These gels redistribute the spectrum by decreasing the concentration of selected wavelengths from the light. If you’re using two 3200k fresnels and one daylight-balanced LED, with the goal to balance all lights to daylight, you will need to apply CTB gel to the 3200k lights to unify the colors. When you light a scene, make sure you’re matching the color temperatures.90005 90008 90004 Looking for more lighting tips and tricks? Check these out. 90005 .90000 Color Temperature (Kelvin) 90001 90002 90003 90004 What is color temperature? 90005 90006 90007 Color temperature is a way to describe the light appearance provided by a light bulb. It is measured in degrees of Kelvin (K) on a scale from 1,000 to 10,000. 90008 90007 Typically, Kelvin temperatures for commercial and residential lighting applications fall somewhere on a scale from 2000K to 6500K. 90008 90007 A light bulb’s color temperature lets us know what the look and feel of the light produced will be.90008 90007 The color temperature of a light bulb is assigned using the basis of correlated color temperature (CCT). 90008 90015 90016 90006 90007 For example, if you heat up a metal object, the object appears to glow. Depending on the Kelvin temperature that the metal object is being heated at, the glow will be various colors, such as orange, yellow or blue. The color temperature of light bulbs is meant to replicate the Kelvin temperature of the metal object. 90008 90007 90008 90015 90023 90004 What color temperature is right for me? 90005 90026 Understanding Kelvin temperature (K) makes it easier to choose lighting that gives you the look and feel you want.90003 90028 90003 90026 90003 90032 90003 90006 90007 At the lower end of the scale, from 2000K to 3000K, the light produced is called «warm white» and ranges from orange to yellow-white in appearance. 90008 90007 Color temperatures between 3100K and 4500K are referred to as «cool white» or «bright white.» Light bulbs within this range will emit a more neutral white light and may even have a slightly blue tint. 90008 90007 Above 4500K brings us into the «daylight» color temperature of light.Light bulbs with color temperatures of 4500K and above will give off a blue-white light that mimics daylight. 90008 90015 .90000 Molecular Expressions Microscopy Primer: Light and Color 90001 90002 90003 Color Temperature 90004 90005 The color temperature model is based on the relationship between the temperature of a theoretical standardized material, known as a 90006 black body radiator 90007, and the energy distribution of its emitted light as the radiator is brought from absolute zero to increasingly higher temperatures. As the name implies, black body radiators completely absorb all radiation, without any transmission or reflection, and then re-emit all incident energy in the form of a continuous spectrum of light representing all frequencies in the electromagnetic spectrum.Although the black body radiator does not actually exist, many metals behave in a manner very similar to a theoretical radiator. 90008 90005 Imagine that the black body radiator is heated to the temperature of freezing water, equal to 273 kelvins (or 90006 K 90007), zero degrees Celsius, or 32 degrees Fahrenheit. There is no obvious difference in the appearance of the radiator. The black body is then further heated to the temperature of boiling water: 373 kelvins, 100 degrees Celsius, or 212 degrees Fahrenheit.Still, no change in appearance occurs. However, if the black body continues to be heated, it will begin to glow and give off its own light. When the temperature reaches 3200 kelvins, the radiator will be emitting light with a visible light wavelength range equivalent to the 90006 color temperature 90007 of the spectrum produced by a tungsten filament, typical of those found in microscope lamps. Heating the black body to even higher temperatures will result in the emission of a wide spectrum of colors, the nature of which is temperature-dependent.90008 90005 The absolute temperature of the black body radiator is expressed in kelvins (usually abbreviated simply as 90006 K 90007, omitting the reference to degrees), which is equivalent to degrees Celsius plus 273 degrees. For example, 1,000 kelvins (or K) equals 727 degrees Celsius. Therefore, we can define the color temperature of a light source as the value of the absolute temperature of a black body radiator when the radiator color spectrum, or 90006 chromaticity 90007, matches that of the light source.In the case of fluorescent lamps, which can only approximate the chromaticity of a black body, the corrected term 90006 correlated 90007 color temperature is applied through a calculated chromaticity value. 90008 90005 Using a black metal pot as a model for the black body radiator (see Figure 1), color changes are first apparent as the pot begins to glow a dull red when heated to a temperature of about 900 K. As the temperature is increased to a range between 1,500 K and 2,000 K, the pot turns from yellowish to brighter red in color.Still further temperature increases, to a range above 3,000 K, transforms the color to a yellow-white (the color temperature of a tungsten filament), and at 5,000 K and above, a bluish-white color appears at the base of the pot ( the color temperature of daylight). Progressive temperature increases of the black body shift a greater proportion of emitted light into the higher frequency regions (shorter wavelengths) of the visible light spectrum. 90008 90025 90026 90027 90028 90029 90006 Interactive Java Tutorial 90007 90028 90033 90028 90035 90026 90037 90035 90039 90005 There are two important points to consider when examining color temperature phenomena.The color temperature value of a light source refers only to the visual appearance of the source, but does not necessarily describe the effect this source will have on photographs or digital images. Also, color temperature does not take into consideration the spectral distribution of a visible light source. In cases where a light source, such as a fluorescent lamp, arc-discharge burner, laser, or gas discharge lamp, does not have a spectral distribution similar to that of a black body radiator, its color temperature alone is not a reliable means of selecting suitable filters or creating look-up tables for color balance corrections.Therefore, although two different light sources may be described as having the same color temperature, exposed photographic emulsions or digital images lacking proper 90006 white balance 90007 baseline adjustments may respond differently to the sources. When using fluorescent lamps or similar light sources, a per-wavelength comparison of sensitivity and spectral output is often necessary to determine the correct filters for color temperature balance. 90008 90005 The concept of color temperature is very important in the traditional photography arena, where film emulsions must be balanced to accurately render color using different light sources.For example, films intended to be used outside in ordinary daylight, fluorescent, and flash lighting are balanced during manufacture for a color temperature of 5500 K while films made for indoor tungsten light bulb use are balanced for a color temperature of 3200 K to 3400 K . The 5,500 K average value of the sun’s color spectrum varies during different parts of the day and is also seasonally and latitudinally dependent. In the early morning and late evening, the color temperature will drop to 5,000 K and below, causing color shifts that result in warmer (redder) color renditions, familiar to some photographers as the «golden hours».Although this wide variation in color temperature is not critical for optical microscopy applications, it does point out the fluctuations that must be addressed in general photography and photographic lighting scenarios. 90008 90005 A majority of the light bulbs that are used for indoor illumination have some form of tungsten filament (with the exception of fluorescent bulbs) and emit a wavelength spectrum centered in the 3,200 K color temperature region. Common fluorescent indoor lamps have a color temperature range between 4,000 K and 5,000 K, more closely approximating daylight lighting conditions.Using daylight-balanced films under tungsten illumination will shift all color tones towards a decidedly yellow cast. Likewise, using tungsten-balanced films under daylight illumination will shift color tones towards a bluer cast. All major film manufacturers have one or several 3200 K films available in 35 mm transparency format. Transparency film is preferable to color negative film for several reasons. First, all color negative films are color balanced for 5500 K and must be manipulated during printing to avoid the yellow cast mentioned above.Most photo processors can not (or will not) produce satisfactory results with photomicrographs on color negative film. Also, the contrast and color saturation in transparency film can not be equaled by color negative film. 90008 90005 The clown photographs presented in Figure 2 illustrate the proper use of color balance between film emulsions and illumination sources. The clown in the center (Figure 2 (b)) was photographed under natural sunlight using daylight-balanced (5500 K) Fujichrome Velvia.Using the same film, the clown on the left (Figure 2 (a)) was photographed under tungsten illumination. Note that all hues are shifted to longer wavelengths and the overall image has a definite yellow cast. The clown on the right (Figure 2 (c)) was photographed under natural sunlight, but this time the film was tungsten-balanced (3200 K) Fujichrome 64T. Under these conditions, the image has an overall blue cast and appears very unnatural. By carefully coordinating lighting conditions with film emulsion, most photographers can easily take beautiful images that accurately reproduce the actual colors of the subject.90008 90005 A comprehensive color temperature chart (see Table 1) can be a valuable resource to help illustrate the range of colors generated by inside (artificial) and outside (natural sunlight) light sources. Values ​​falling below 3,500 K are generally considered to be in the 90006 tungsten 90007 range, and neutral colors viewed under this illumination often appear redder (90006 warmer 90007) than they do under natural daylight. With digital imaging using video tubes and CCD image sensors, color temperature becomes less of a concern because digital techniques eliminate the need for photographic films and their inherent color temperature sensitivities.However, the electronic equipment utilized to capture digital images must contain functions that enable the adjustment of a white balance setting to establish a baseline for color temperature. 90008 90005 Accepted convention for evaluation of light sources, in regards to filter requirements for color balance adjustment, employs the reciprocal of color temperature, which is referred to as 90006 microreciprocal degrees 90007 (or 90006 mireds 90007, when multiplied by a factor of one million) .This quantitative approach is useful because a given sum of reciprocal units corresponds approximately to the same color difference for most light sources that emit in the visible spectrum (in the range from 1000 K to 10,000 K). For instance, a color conversion filter that produces a 100 K color temperature decrease in a 3,200 K light source will produce a decrease of about 1,000 K in a 10,000 K light source. Although the color temperature differential between conversion of the 10,000 K and 3,200 K light sources is 1,000 K and 100 K, respectively, the actual filtration difference is virtually the same when compared as mired units (10 versus 11 mireds).90008 90005 More recently, the term 90006 reciprocal megakelvins 90007 (90006 1 / MK 90007) has been used by Kodak and others to replace mireds. Color temperature quantities expressed in reciprocal megakelvins have the same value as mireds, but the number is determined by first expressing the color temperature in megakelvins (90006 1 MK = 1,000,000 K 90007) and taking the reciprocal. 90008 90003 Color Temperatures of Common Light Sources 90004 90025 90026 90074 90075 90026 90077 90078 90079 90029 90006 Daylight Sources 90007 90028 90029 90006 Color Temperature 90002 (K) 90007 90028 90035 90090 90029 90006 Skylight 90007 90028 90029 90006 12000 to 18000 90007 90028 90035 90100 90029 90006 Overcast Sky 90007 90028 90029 90006 7000 90007 90028 90035 90090 90029 90006 Noon Sun / Clear Summer Sky 90007 90028 90029 90006 5000 to 7000 90007 90028 90035 90100 90029 90006 Noon Sun / Clear Winter Sky 90007 90028 90029 90006 5500 to 6000 90007 90028 90035 90090 90029 90006 Photographic Daylight 90007 90028 90029 90006 5500 90007 90028 90035 90100 90029 90006 Noon Sunlight 90002 (Date Dependent) 90007 90028 90029 90006 4900 to 5800 90007 90028 90035 90090 90029 90006 Average Noon Sunlight 90002 (Northern Hemisphere) 90007 90028 90029 90006 5400 90007 90028 90035 90100 90029 90006 Sunlight at 30-Degree Altitude 90007 90028 90029 90006 4500 90007 90028 90035 90090 90029 90006 Sunlight at 20-Degree Altitude 90007 90028 90029 90006 4000 90007 90028 90035 90100 90029 90006 Sunlight at 10-Degree Altitude 90007 90028 90029 90006 3500 90007 90028 90035 90090 90029 90006 Sunrise and Sunset 90007 90028 90029 90006 3000 90007 90028 90035 90079 90029 90006 Artificial Sources 90007 90028 90029 90006 Color Temperature 90002 (K) 90007 90028 90035 90090 90029 90006 White LED 90007 90028 90029 90006 6500 to 9500 90007 90028 90035 90100 90029 90006 Electronic Flash 90007 90028 90029 90006 5500 to 6500 90007 90028 90035 90090 90029 90006 Xenon Burner 90007 90028 90029 90006 6000 90007 90028 90035 90100 90029 90006 White Flame Carbon Arc 90007 90028 90029 90006 5000 90007 90028 90035 90090 90029 90006 Warm White Fluorescent Tubes 90007 90028 90029 90006 4000 90007 90028 90035 90100 90029 90006 Aluminum-Filled Flash Bulbs 90002 (M2, 5, & 25) 90007 90028 90029 90006 3800 90007 90028 90035 90090 90029 90006 500-Watt 3400 K Photoflood 90007 90028 90029 90006 3400 90007 90028 90035 90100 90029 90006 12 Volt / 100 Watt 90002 Tungsten-Halogen @ 9 Volts 90007 90028 90029 90006 3200 90007 90028 90035 90090 90029 90006 12 Volt / 50 Watt 90002 Tungsten-Halogen @ 9 Volts 90007 90028 90029 90006 3200 90007 90028 90035 90100 90029 90006 100-Watt Household Lamp 90007 90028 90029 90006 2900 90007 90028 90035 90090 90029 90006 40-Watt Household Lamp 90007 90028 90029 90006 2650 90007 90028 90035 90100 90029 90006 Gaslight 90007 90028 90029 90006 2000 to 2200 90007 90028 90035 90090 90029 90006 Candlelight 90002 (British Standard) 90007 90028 90029 90006 2900 90007 90028 90035 90039 90028 90035 90039 90028 90352 90028 90035 90026 90356 90028 90358 90028 90035 90039 90005 90006 Table 1 90007 90008 90005 An important question for the microscopist is how to ensure that the color temperature of light reaching the film or image sensor matches the film’s color temperature or falls within the range of the digital look-up tables.The color temperature of light emanating from the heated coil of a tungsten-halogen bulb is dependent on the voltage supplied to the bulb in order to heat its filament. Tungsten and tungsten-halogen lamps emit a 90006 continuous spectrum 90007 of energy that is manifested by a relatively constant output for each wavelength. A majority of the energy emitted by these lamps is in the long wavelength part of the spectrum (red and higher), and they subsequently produce a tremendous amount of heat that is not useful for illumination.In fact, about 90 percent of the energy emitted by tungsten and tungsten-halogen lamps is released in the form of infrared radiation and heat, which does not contribute to illumination in the visible region. The ultraviolet, visible, and infrared spectrum of a typical tungsten lamp is illustrated in Figure 3 for three specific color temperatures. Note that the spectral distributions are similar for each color temperature, with the ratio of blue to red increasing as color temperature is increased by raising the voltage applied to the lamp.90008 90005 Table 1 catalogs the color temperature of several common microscope bulbs and a variety of other light sources providing either natural or artificial illumination. For tungsten and tungsten-halogen lamps, the greater the voltage setting of the microscope’s step-down transformer, the higher the color temperature of the emitted light. As the voltage is raised, the white light becomes more bluish; as the voltage is reduced, the light becomes more reddish-yellow. Once the voltage for color photomicrography or digital imaging has been correctly set, the voltage regulator is no longer used to adjust brightness, because such an adjustment will affect the color temperature of film or the white balance on a digital imaging sensor.High-intensity and ultra high-intensity white light emitting diodes have recently been introduced as light sources for optical microscopy, and have color temperatures ranging from 6,500 K to 9,500 K, rivaling daylight (See Table 1). 90008 90005 The test of properly balanced light, matched to the film’s design or a digital camera look-up table, is to have the clear background of a photomicrograph or digital image appear white. A bluish background indicates too high a color temperature, while a yellowish background signifies too low a color temperature (see Figures 2 and 7).To facilitate obtaining the correct setting for photomicrography or digital imaging, many modern microscopes have a 90006 photovoltage 90007 button that, when pressed, automatically sets the 12 volt 100-watt halogen lamp at 9 volts, or the 6 volt 20-watt halogen lamp at 5 to 6 volts to deliver light approximating 3,200 K. While the most common bulbs (12 volt, 100-watt halogen; or 6 volt 20-watt or 30-watt halogen) can be set to yield a color temperature close to 3,200 K, none of these bulbs (except the xenon and mercury burners) can radiate light suitable for daylight-balanced films.In order to produce light simulating daylight quality, a color 90006 conversion filter 90007 must be placed in the light path, either on the light port of the microscope or in a built-in holder. 90008 90005 90006 Color Conversion and Balancing Filters 90007 90008 90005 The most common variety of conversion filter (producing large jumps in color temperature) is the Kodak 80A filter (3,200 K to 5,500 K) or the related 80B, 80C, 80D series of filters (see Figure 4). For Olympus microscopes, the equivalent daylight-balanced filter is called the LBD filter, and for Nikon microscopes the filter is termed the NCB filter.Kodak 80-series conversion filters display an absorption maximum centered in the 600-650 region of the visible spectrum, which includes most of the yellow and red wavelengths. The 80A filter has the highest extinction coefficient and thus, by absorbing more red and yellow light, will produce the greatest shift in effective color temperature, followed by the 80B, 80C, and 80D. 90008 90005 For small increases in color temperature, the light blue Kodak 82-series filters can be used. Conversely, for small drops in color temperature, the light yellow Kodak 81-series filters are employed.When attempting to convert the color temperature of a daylight-balanced microscope light source, such as a xenon lamp or flash tube, for use with tungsten-balanced color film, one of the appropriate amber Kodak 85-series filters is inserted. Although it is far more practical to utilize a microscope equipped with a tungsten-halogen light source, especially for critical photomicrography, these filters will serve in cases where it is impossible to use other lamps (such as microscopes equipped with arc-discharge burners or flash tubes).90008 90005 The «fine tuning» filters (Kodak series 81, 82 and similar filters), useful for making smaller adjustments (100 K to 600 K) to color temperature, are called 90006 color balancing 90007 filters as opposed to color 90006 conversion filters 90007 that produce large changes (several thousand kelvins) in color temperature. A color temperature 90006 nomograph 90007 can determine the appropriate filter selection required to convert from a known starting color temperature to a desired color temperature (Figure 5).To use this type of graph, a straight edge ruler is placed at the color temperature of the original source and is pivoted to connect to the desired color temperature. The region where the ruler intersects the central axis identifies the filter necessary to achieve the color conversion. A more convenient method of determining the appropriate color temperature conversion filter for color balance adjustment employs a color temperature conversion calculator, which can be found in a variety of reference volumes on the subject.90008 90005 The Kodak 82-series filters (Figure 6), light blue in color, are useful for making small incremental increases to the color temperature of light sources that produce a color balance less than 3,200 K to 3,400 K. Filters of this type do not actually change the color temperature of the light source, but are useful in simulating a higher color temperature for the purposes of photomicrography. There are four filters in this series: 82, 82A, 82B, and 82C (see Figure 6 for transmission profiles in the visible region), and each successive filter in the series raises the color temperature by an additional 100 K increment.For example, if a light source has a color temperature of 3,000 K (often found in older microscopes with a tungsten lamp), the microscopist could adjust the apparent color temperature to 3,200 K with an 82A filter for use with type B tungsten-balanced film , or to 3,400 K with an 82C filter for use with type A film. These filters should be an essential part of any photomicrographer’s toolkit. 90008 90005 In situations where the color temperature of the light source is too high for a particular film, Kodak offers the 81-series filters (Figure 6).These filters are light yellow in color and produce simulated incremental decreases in color temperature in a similar, but opposite manner from the 82-series filters. Because color temperature in microscope light sources is only rarely too high, these filters are seldom used in photomicrography. An exception to this is the application of 81-series filters to fine tune photomicrographs produced on tungsten-balanced film when using a daylight illumination source, such as a xenon lamp or electronic flash tube.90008 90005 Some microscopes are equipped with a filter termed a 90006 daylight blue 90007 filter. This is not a filter designed for photomicrography, but is meant to produce a gray-blue background in the field of view for comfortable observation. Always remove daylight blue filters during photomicrography and digital imaging sessions, or when attempting to fine-tune a light source with color balancing filters. 90008 90005 Color balancing filters and color conversion filters can be purchased as glass filters of various diameters or as the relatively inexpensive Kodak Wratten filters, which are available in thin, lacquered gelatin 2-inch or 3-inch squares.Wratten filters are produced by dissolving suitable organic dyes in liquid gelatin and coating the surface of an optical glass plate with a thin film of the solution. After drying, the gelatin film is stripped from the glass plate and coated with lacquer. Gelatin filters prepared in this manner have a thickness of 0.1 millimeter 0.01 millimeter, and exhibit a uniform thickness distribution across the width that renders them suitable for precise work in optical microscopy with negligible effect on image quality and virtually no increase in optical path length.90008 90005 In modern microscopes that use tungsten-halogen lamps, the color temperature produced by the lamp is usually very close to 3,200 K, but often declines with age. Older microscopes, which may use a number of different 6 or 12-volt tungsten or tungsten-halogen lamps from a variety of manufacturers, often deviate (sometimes markedly) from 3,200 K in color temperature. In this case, the actual color temperature of the light source is usually unknown. Other factors that may affect color temperature are optical absorption, diffusion from filters, and reflections within the microscope optical train and illumination system.When any of these circumstances occur, the color temperature of illumination at the film plane or surface of the digital image sensor may differ markedly (as much as 200 K) from that emitted by the lamp. Usually, color temperature variations induced by artifacts in the microscope optical system tend to lower (rather than raise) color temperature. 90008 90005 In practice, microscopists usually determine the correct filters for color temperature adjustments by trial-and-error, especially when attempting to convert illumination from an unknown value near 3,200 K into 5,500 K for daylight-balanced films.A good starting place for microscopes with tungsten or tungsten-halogen lamps is the Kodak 82-series light balancing filters. These filters have absorption spectra that display maxima with relatively high extinction coefficients in the 625-700 nanometer region (see Figure 6), which covers most of the yellow and red wavelengths of the visible spectrum. By absorbing a higher percentage of the longer (red) visible wavelengths incident on the filter, the Kodak 82-series filters are able to increase the effective color temperature of light.90008 90005 The 81-series filters are able to decrease the effective color temperature of light by absorbing wavelengths in the blue (350-500 nanometers; Figure 6) region of the visible spectrum. An absorption maximum at 400 nanometers occurs for each of the 81-series filters, with the extinction coefficient for this maximum increasing in a periodic manner as the filter density is increased from the 81 filter through the 81EF filter. Each incremental increase in the extinction coefficient corresponds to approximately a 100 K change in color temperature.The same successive extinction coefficient increase is seen in the 82-series filters, which also corresponds to a 100 K change in color temperature for this series of filters. 90008 90005 If the initial color temperature is unknown, a series of tests (much like 90006 exposure bracketing 90007 in photography) should be conducted to determine the exact amount of filtration necessary to bring the microscope light source into the desired balance. When using tungsten-balanced film no other filters should be added, but when using daylight-balanced film a Kodak 80A, Olympus LBD, or Nikon NCB filter should be inserted into the light path prior to experimenting with the Kodak 82-series filters to fine -tune the color temperature.90008 90025 90026 90027 90028 90029 90006 Interactive Java Tutorial 90007 90028 90033 90028 90035 90026 90037 90035 90039 90005 Some higher-end photomicrographic cameras (Olympus PM-20 and PM-30) have a color temperature meter accessory, which can be used to read the color temperature as various filters are placed in the light path, even at low illumination levels. A light emitting diode (90006 LED 90007) scale indicates the reference point against which the reading will be calibrated.The Olympus color temperature module will measure color temperature in the range of 2,500 K to 10,000 K. Color temperature measurements are conducted with the specimen temporarily removed from the light path. Although expensive, this valuable option takes any guesswork out of determining exact color temperatures. 90008 90005 Several locations are useful for adding color balancing filters to the optical path of a microscope, but these filters should always be added somewhere between the light source and the substage condenser.Some microscopes are equipped with a filter tray between the lamphouse and the field lens, which is capable of holding diffusion filters, heat-absorbing filters, and color correction filters. Newer microscopes often have a built-in 90006 daylight 90007 conversion filter (90006 LBD 90007 for Olympus and 90006 NCB 90007 for Nikon) housed within the base of the microscope that can be toggled into and out of the optical pathway. Many older microscopes have a filter tray built into the base of the substage condenser that will hold one or several color correction filters.To avoid dirt and flaws on the filter surface being imaged in the specimen plane, special care should be taken to place the filters at a sufficient distance from the field diaphragm or any other image-forming conjugate planes. 90008 90005 90006 White Balance Calibration in Digital Imaging 90007 90008 90005 As discussed previously, the color balance of a digital image is heavily influenced by the spectrum of wavelengths collected by the CCD or CMOS image sensor, regardless of whether the sensor is housed in a camera, telescope, laser bench, or microscope.In color digital cameras that employ these solid-state devices, a range of balance adjustments is often necessary in order to produce acceptable color images that conform to the color temperature of the illumination source. 90008 90005 The human eye is designed to readily adapt to changing illumination conditions in order to identify a white object as white even when the surrounding intensity and color temperature fluctuate. In contrast, digital cameras require careful scrutiny and adjustment of the red, green, and blue (90006 RGB 90007) signal amplitudes in order to produce similar results.A majority of digital cameras require measurement and adjustment of the color temperature to ensure that a white object is recorded as white, and to guarantee that other colors fall within acceptable limits. This process is often referred to as adjusting the white balance, and is a software and / or hardware option on many digital cameras. 90008 90005 To exemplify the point, a typical example of color temperature (or color balance) errors in digital images captured through a microscope is presented in Figure 7.A brightfield image of stained 90006 90453 Lumbricus terrestris 90454 90007 (the common earthworm) tissue was captured before and after adjusting the white balance look-up tables. Before adjusting the white balance setting (Figure 7 (a)), the image has an overall green cast that softens the eosin and hematoxylin stain and masks the background color (which should appear white or a light neutral gray). After adjustment of the microscope’s white balance look-up tables, the bright stain colors are devoid of any cast and reveal uniform distribution within the tissue (Figure 7 (b)).In addition, the background has been shifted to a very light neutral color that is commonly observed when imaging specimens in brightfield illumination. 90008 90005 The best white balance correction is often achieved when a digital camera is pointed at a white card instead of a colored object, or the specimen is completely removed from the microscope stage to achieve an evenly illuminated background. Setting the white balance with a specimen in place may cause the images to acquire a color cast, which can seriously impair image contrast and result in colors that deviate from those of the object or specimen.In addition, images viewed in polarized light, differential interference contrast, fluorescence, or other contrast enhancing techniques can present more difficulty in color balance adjustment. This usually occurs when backgrounds assume a tint due to the optical configuration of the camera or microscope. For example, when a first-order retardation plate is inserted between the polarizer and analyzer in polarized light microscopy, the entire viewfield appears magenta, which makes white or black balance adjustment very difficult.A similar effect is observed in differential interference contrast microscopy. In many cases, the black balance value is much easier to establish, leading to much sharper images with jet black backgrounds and a significant improvement in overall image contrast. 90008 90025 90026 90027 90028 90029 90006 Interactive Java Tutorial 90007 90028 90033 90028 90035 90026 90037 90035 90039 90005 Modern consumer and scientific CCD digital camera systems usually incorporate reference circuitry that contains a digital signal processor (90006 DSP 90007) circuit designed to electronically adjust the color balance of images recorded by the sensor.The processing circuitry provides a series of look-up tables, which are utilized by the software to adjust the red, green, and blue signals in order to arrive at the proper color balance for a specific illumination intensity and color temperature. Often, the look-up tables will contain information about tungsten-halogen lamps (at a variety of color temperatures), mercury and xenon arc-discharge burners, flash tubes, light emitting diodes, among other common illumination sources. The RGB system is one of the primary color models utilized to specify and represent colors in computer-controlled cameras and software.White is produced by combining equal parts of all three colors (red, green, and blue) at levels of 100 percent. Adjustments for color temperature can easily be made by adjusting the intensity level of one or more of these primary colors. 90008 90005 In addition to the camera system, the computer or video monitor utilized to view images often requires a corresponding adjustment for color temperature in order to match color information collected by the digital camera. Many computer software packages contain a 90006 white point 90007 algorithm that enables adjustment of the software to match color temperature, but the hardware must often be adjusted as well.Computer monitors usually have external adjustments that allow the user to toggle between several choices of color temperature, ranging from about 9000 K down to 5000 K. These settings can be changed to match standard viewing conditions and to ensure that the image seen on the screen truly represents the one captured by the camera. 90008 90005 In conclusion, a lack of proper color temperature balance between the microscope light source and the film emulsion or image sensor is the most common reason for unexpected color shifts in photomicrography and digital imaging.If the color temperature of the light source is too low for the film, photomicrographs will have an overall yellowish or reddish cast and will appear 90006 warm 90007. On the other hand, when the color temperature of the light source is too high for the film, photomicrographs will have a blue cast and will appear 90006 cool 90007. The degree of mismatch will determine the extent of these color shifts, with large discrepancies leading to extremes in color variations. Perhaps the best example is daylight film used in a microscope equipped with a tungsten-halogen illumination source without the benefit of color balancing filters.In this case, the photomicrographs will have a quite large color shift towards warmer reddish and yellowish hues. As problematic as these color shifts may seem, they are always easily corrected by the proper use of conversion and light balancing filters. 90008 90005 90006 Contributing Authors 90007 90008 90005 90006 Mortimer Abramowitz 90007 — Olympus America, Inc., Two Corporate Center Drive., Melville, New York, 11747. 90008 90005 90006 Thomas J.Fellers 90007 and 90006 Michael W. Davidson 90007 — National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310. 90008 90502 90005 90006 BACK TO COLOR TEMPERATURE 90007 90008 90003 Questions or comments? Send us an email. 90004 90509 © 1998-2019 by Michael W. Davidson and The Florida State University. All Rights Reserved. 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