Guideline: which colour temperature shall I choose for my LED?
Colour Temperature Explained!
With the introduction of the i5t Plus, Olight Fans have an exciting opportunity to select between a comprehensive offering of color temperatures for the first time. But what is color temperature? How is it measured? Which one will work best for me? In this post we will answer these questions, as well as very briefly and in very simple terms discuss how LEDs work, how different color temperatures are achieved, what each color temperature is useful for, and what compromises come along with that.
What is color temperature?
You may have heard the terms “cool white” and “neutral white” and “warm white” being used to describe a flashlight’s beam. This concept is referred to as colour temperature, or sometimes referred to as beam tint. The scale used to quantify colour temperature is CCT (Correlated Color Temperature) which is measured in the units Kelvin (K). You might recognize Kelvin as a unit of thermal temperature. But don't get confused, the thermal temperature of the flashlight in your hand does not enter into this discussion at all. Kelvin was chosen to represent color temperature of light, because different materials will glow a different color when heated to different temperatures. Just like a steel rod heated in a forge, first it glows red hot, then it glows yellow, and so on as the temperature increases. But instead of steel, this scale is based on what color a hypothetical idealized material would glow if heated to a given temperature in degrees Kelvin. Higher Kelvin means the light will have a more blueish hue. Lower Kelvin indicates a more amber tint to the light. This may seems backwards, but just remember, as the temperature of the steel goes up, the warmth of the light it gives off goes down. But how does this work? To explain how LEDs create white light, I’ll briefly oversimplify how an LED functions.
How Do LEDs work? How do they make different types of white light?
Keeping things very simple; LEDs work by passing electricity through a semiconductor, also called a diode. This action emits light due to electroluminescence. This type of light is very blue in color, and heavily towards the ultraviolet spectrum. In order to convert the UV light to a useful illumination, a layer of phosphor compound is placed over top of the diode. These phosphor compounds absorb and are energized by the UV light, causing the phosphor to fluoresce at different colors depending on the compound. In the early days, the phosphor could only convert some of the blue light into other colors, allowing the remaining blue light to join the beam, producing a cool white light. That’s how early LED flashlights came to have their iconic blueish hue. But as technology progressed, engineers were able to develop different phosphor compounds and methods to create the wide array of color temperatures that are available today. But how is this fluorescent light manipulated to emit a white light at a desired temperature?
What makes light more white?
All visible light is made up various wavelengths of light. Everyone has seen an image of a prism taking white light and splitting into its different colors, or wavelengths. Well an LED does the same thing but in reverse. Since all LEDs start off by emitting blue light, LEDs produce cool white light as default. Using different compound compositions and layering, more of that blue light can be absorbed by the phosphor layer, causing it to fluoresce with a different distribution of wavelengths. As seen in the diagram below, When these distributions are heavier in the shorter blue wavelengths, the light appears cool. Longer wavelengths are towards the red side of the spectrum, and when the distribution is heavy into the red side of the spectrum, that contributes to a more warm amber tint to the light. There is a trade-off that happens here. As the phosphor compounds convert more blue light into other wavelengths, less of that original blue light joins the beam. This means that as the color temperature decreases (tint gets warmer), the maximum overall output necessarily reduces. So how does the color temperature you select effect the lights operation in everyday use? I’m glad you asked.
Practical applications and considerations - What is each color temperature useful for?
First and foremost, color temperature is almost entirely a matter of personal preference. Don’t let anyone tell you you’re wrong for liking the temperature that looks best to you. Also it’s important to note that the terms cool, neutral and warm, have no strict definition. They are just descriptive words that tell you what range of color temperature you can expect. With that said, here are some basic guidelines to consider when evaluating a light in any given colour temperature range.
Cool white (CW)
Cool white is usually used to describe the range between 4600K-6500K. Cool white is popular for a few reasons. Most people think the iconic blueish white tint of an LED signals how modern and powerful it is. Modernity is a misconception, however, they are right about power. All else being equal, cool white is brighter than other tints. So if brightness is your highest priority in a flashlight, cool white makes a great choice. That is also why it has been featured in a majority of Olight models up to this point. However, some people report that cool white can come with harsh glare off of reflective surfaces like glass or water. The glare factor can be reduced if you choose a different tint.
IDEAL USE CASE: General EDC use, industrial applications, and on-duty use. Perfect in any situation where brighter is better.
Neutral white (NW)
Neutral white describes the range of temperatures in between warm and cool, usually in the 3100K-4500K range. Benefits of neutral white include the perception that the objects you are illuminating appear more vivid and lifelike in color. That perception is largely because neutral white is much closer to day light compared to the more artificial looking cool white. Many people report that colors seem more accurate, because you are looking at them with light that more closely resembles the full spectrum of wavelengths that come from sunlight. This effect is most noticeable when outdoors, looking at green trees, or brown underbrush. But even indoor spaces can appear more realistic using neutral white. Now like we discussed, neutral white does comes with slightly less maximum brightness. However, the difference in brightness between cool and neutral tint is fairly minimal. As the color temperatures start to get warmer than neutral, the drop in output begins to be more noticeable.
IDEAL USE CASE: Auto Mechanics, general EDC use, and explosive ordinance disposal. For occasions when you really don't want to cut the wrong color wire.
Warm white (WW)
Warm white is typically in the range between 2200-3000K. Warm white can look more like candlelight, and in that way is a quite comforting choice for area lights. With the relative absence of blue light, warm white can in general be less disturbing to your sleep cycle as well. But in a flashlight context, the main advantage of warm white for its ability to defeat airborne particulate obstructions such as rain, smoke or dust, without distracting reflections or offensive glare. This is due to the majority of the wavelengths of the light being longer, and therefore are less susceptible to refraction. Particularly noticeable when used in heavy precipitation, fog, dust or smoke. So if you operate in dusty or foggy environments, warm white is an astute choice. As discussed previously warm white will not have the same maximum brightness as the same light in CW or NW. It appears slightly dimmer than neutral, and noticibly dimmer that cool white. And lastly, as a tertiary consideration, warm white is quite a novelty to see in the Olight lineup, it definitely can’t hurt to have one around, or to add one to your collection… so get it while it’s warm!
IDEAL USE CASE: Tow truck drivers, midnight snack expeditions, use in adverse weather conditions, and lighthouse keeping. For when you call out to the sea, and the sea shouts back.
If you made it this far, please leave a like on this blog post, and take a moment to browse the May flash sale offerings. Hopefully you will enjoy the rest of your day a bit entertained, and a bit more informed than when you started.