Lumens to candela and candela to lumens calculator. Lumens to Candela and Candela to Lumen Calculator Maximum Light Intensity iv max mcd
Lumen (lm, lm)- unit of measurement of luminous flux in SI. Where SI is a system of units of physical quantities, (fr. Le Syst? me International d "Unit? s, SI).
One lumen is equal to the luminous flux emitted by a point isotropic source with a luminous intensity equal to one candela into a solid angle of one steradian (1 lm = 1 cd? sr). The total luminous flux created by an isotropic source with a luminous intensity of one candela is 4? lumens.
A typical 100 W incandescent lamp produces a luminous flux of approximately 1300 lm. The 26 W compact fluorescent lamp produces a luminous flux of approx. 1600 lm. The luminous flux of the Sun is 3.63 10 to the 28th power of lm.
Lumen is the total luminous flux from a source. However, this measurement usually does not take into account the focusing efficiency of a reflector or lens and is therefore not a direct measure of brightness or useful beam performance. A wide beam of light can have the same lumens as a narrow beam. Lumens cannot be used to determine the intensity of a beam, because the lumen rating includes all of the scattered, useless light.
Lux (lx, lx)- a unit of measurement of illumination in the SI system.
Lux is equal to the illumination of a surface with an area of 1 sq m with a luminous flux of radiation falling on it, equal to 1 lumen.
100 lumens were collected and projected onto a 1 meter square area. Illumination of the area will be 100 lux. The same 100 lumens directed at 10 square meters will give an illumination of 10 lux.
Candela (cd, cd)- one of the seven basic units of the SI system, equal to the intensity of light emitted in a given direction by a source of monochromatic radiation with a frequency of 540 10 to the 12th power of Hz, the energy intensity of which in this direction is (1/683) W / sr. Steradian?n (Russian designation: sr, international: sr) is a unit of measurement of solid angles.
The selected frequency is green. The human eye is most sensitive in this region of the spectrum. If the radiation has a different frequency, then a greater energy intensity is required to achieve the same light intensity.
Previously, the candela was defined as the intensity of light emitted by a black body perpendicular to a surface of 1/60 sq cm at the melting point of platinum (2042.5 K). In the modern definition, the factor 1/683 is chosen so that the new definition matches the old one.
The strength of light emitted by a candle is approximately equal to one candela (Latin candela - candle), so this unit of measurement used to be called a “candle”, now this name is obsolete and is not used.
Light intensity of typical sources:
| Source | Power, W | Approximate light intensity, cd |
| Candle | 1 | |
| Modern (2016) incandescent lamp | 100 | 100 |
| Ordinary LED | 0,015 | 5 mcd |
| Super bright LED | 1 | 25 |
| Super bright LED with collimator | 1 | 1500 |
| Modern (2016) fluorescent lamp | 20 | 100 |
Black Diamond is a trendsetter in the world of professional mountaineering and climbing equipment. The brand produces high-quality head and pendant lights that can be used even at a depth of one meter under water for half an hour. BD offers travel lighting products with lumen outputs up to 200 lumens and relatively light weight. Many flashlights are endowed with several lighting modes for the convenience of working on a climbing route and at home. Bright, light, neat and practical, BlackDiamond flashlights will not let you down even in the most extreme situation.
Luminous flux of lamps (lm)
big LED-high, big LED-med, big LED-low, 5 MM - High, 5 MM - medium, 5 MM - low
| Lantern Black Diamond (BD) | Luminous flux, (lm) |
| icon | 200 |
| Spot new | 200 |
| Cosmo new | 90 |
| wiz new | 30 |
| Ion | 80 |
| Ember Power Light | 150 |
| Orbit Lantern | 105 |
| Voyager Lantern | 140 |
| Petzl lantern | Luminous flux (lm) |
| Tikka XP | 180 |
| MYO XP | 140 |
LED BRIGHTNESS
What the consumer is most interested in when choosing LEDs for lamps and other lighting devices is not the current consumption, not the dimensions, and not even the service life, but the brightness. As you know, brightness is denoted by the letterL, this is a luminous quantity equal to the ratio of the luminous flux d2 to the geometric factor ddAcos: L = d2/ddAcos. Where d is the solid angle filled with radiation, dA is the area of the area emitting radiation, or the angle between the perpendicular to this area and the direction of radiation. In other words, brightness is the ratio of the luminous intensity of the I element of the surface to the area of its projection perpendicular to the direction under consideration: formula L = dI/dA cos . The brightness can also be formulated in terms of the ratio of illumination E at a point in the plane perpendicular to the direction to the source to the elementary solid angle in which the flow that creates this illumination is enclosed: the formula L = dE / dcos. Luminance is measured in candela per meter to the minus second power: cd m-2. Brightness, is directly related to visual sensations, since the illumination of the image of an object on the retina is proportional to the brightness of this object.
With regard specifically to the brightness of LEDs, it represents the total power released in the form of light - radiant energy or radiant flux, and it is measured in watts. But how bright an object turns out to be will also depend on additional factors: how much radiant flux is released in the direction of the observer and how sensitive the observer is to the wavelength of light.
Here we introduce the concept of steradian - solid angle, solid solid angles. Simply put, a cone with a vertex at the light source. If the radiant flux of a source - an LED or a lamp - is the same in all directions, the radiant intensity will be equal to the total radiant flux divided by 12.57 steradians, the spatial angle of a full sphere. In LEDs, the radiant flux is concentrated in the beam, and the intensity of the radiation will be equal to the radiant flux divided by the spatial angle of the beam. The width of the angles is usually indicated in degrees, and the intensity of the radiation is usually expressed in milliwatts per steradian mW / sr., which makes it necessary to convert the beam angle to steradians: sr = 2 π (1 - cos(θ/2)), where sr is the solid angle , in steradians, and θ is the beam angle.
Light output is measured in lumens and luminous intensity is measured in lumens per steradian and is called the candela. The relationship between luminous flux, luminous intensity and beam angle means that focusing on an LED in denser beams at a decreasing beam angle will increase luminous intensity (i.e. brightness) without increasing luminous flux. Therefore, when buying an LED for lighting, a 1000 mC LED with a 45° FOV will give the same amount of light as a 10,000 mC LED with a 12° FOV. The LED, as we can see, is quite bright, but this brightness is narrowly directed.
The brightness of LEDs is usually measured in millicandelas - 1 mcd = 0.001 candela. Ordinary Soviet LEDs have a brightness in the range of 20 - 50 mcd, and super-bright LEDs can reach 20,000 mcd and higher. To make it even clearer, I note that a typical 100 W incandescent lamp produces about 1500 lumens, and if the light is emitted equally in all directions, it will have a brightness of about 120,000 mcd. But if the beam is narrowly directed at an angle of 20°, it will have a brightness of about 16,000,000 mcd. So the LEDs, even
Lumen(symbol: lm, lm) - a unit of measurement of luminous flux in SI.
The number of lumens indicates how much light the lamp emits in all directions. The higher the number of lumens, the more light.
One lumen is equal to the luminous flux emitted by a point isotropic source, with a luminous intensity equal to one candela, into a solid angle of one steradian (1 lm = 1 cd × sr). The total luminous flux created by an isotropic source with a luminous intensity of one candela is 4π lumens.
Candela(symbol: cd, cd) is a unit of luminous intensity in SI (from the Latin candela, candle).
The number of candela indicates how much light a lamp emits in one direction, in which it shines most intensely.
One candela is the intensity of light in a given direction from a source of monochromatic radiation with a frequency of 540 * 1012 Hz, (555 nm, green) having an intensity of radiation in this direction equal to 1/683 W in a solid angle equal to one steradian.
Lumens to Candela Converter
The recalculation is carried out according to the formula:
F v =I*2π(1-cos(α)), where
F v - luminous flux
I v - light intensity
α - half brightness angle
To calculate, enter the angle and luminous intensity (luminous flux). Please note that the calculation results depend on the optical parameters of the LED and give an approximate result!
| Candela to Lumen | lumens to candela | |||||
| The power of light, MKD |
half angle brightness |
light stream, mlm |
half angle brightness |
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| Luminous flux, mlm: | Light intensity, mcd: | |||||
Luminous flux of typical light sources
The comparative parameters of some light sources are given, the values are approximate, only for a comparative assessment.
Radiation power, relationship between light energy (Watts) and luminous flux (lumens)
An important parameter for evaluating the energy efficiency of an LED emitter is the ratio between the radiated power and the power released in the form of heat.
The light emitted by the LED, as you know, has a certain energy and the energy of light depends on the wavelength. However, the intensity of light is not proportional to the energy of light radiation, but depends on the sensitivity of the human eye. In other words, the power of light is the power of light radiation, which is available for perception by the human eye. To convert the radiated energy (Watts) into a luminous flux (lumens), you need to know the wavelength of the radiation and the sensitivity curve of the human eye. It is easy to guess that for monochrome radiation this problem can be easily solved, but for a white LED, it is also necessary to know the spectrum of its radiation and perform a rather complicated integration.
It can be estimated that a 1 W white LED with an efficiency of 100 lm/W emits 0.4 W as light and dissipates 0.6 W as heat, while an incandescent lamp emits only 6 W out of 100 W consumed in the visible region of the spectrum (0 .06 W per 1 W).
The energy consumed by the light source from the mains is not completely converted into radiation. This is especially true for LED lamps. In addition to energy losses in the LED itself, power is lost in the power converter, part of the light is delayed by optics - reflectors, diffusers, lenses. When using an LED with an efficiency of 100 lm / W, the lamp efficiency rarely reaches 80 lm / W, and for the most common products it is 60-70 lm / W. As a result, modern mass-produced lamps are about 10 times more efficient than incandescent lamps.
I don't really like formulas. Like any normal person :) They give me a headache and a desire to throw something at the wall. All my life I tried to stay away from them. And it did work. But then I became interested in LEDs and realized that you can’t get anywhere. To get the desired result, you need to understand how it works. Slowly, step by step, I began to wade through the wilds of lumen, candela, steradian. Gradually, a picture began to form in my head. And at the same time regret - well, why was there no one to explain this in a simple, accessible language? So much time wasted ... I'll try to save you from a headache and explain as clearly as possible what an LED is and how it works. Well, at the same time I will explain a couple of laws of optics :)
The article is dedicated to those who get confused in watts-candela-lumens-lux. And yes, LEDs in general. Written by an advanced teapot for beginner dummies :)
Ordinary LED - what it is eaten with
The first semiconductor in history was Ivan Susanin.
Like it or not, but first you have to touch on the laws of ordinary electricity. In illustrative examples, of course :) We all know what 220 volts is - this is something that can hit properly if you do not take precautions. When you buy an electrical appliance, for example, an iron, it is written in the passport what voltage it is designed for. Usually it is 220 volts. But in the same passport such parameters are also indicated - an alternating voltage with a frequency of 50 hertz. Why do manufacturers stubbornly indicate these parameters for you? Pick up any technical passport for an electrical appliance and look - it says that the supply voltage should be - ~ 220 volts, 50 Hz. Let's see what it is. The "~" sign means that the voltage must be AC. In an automobile on-board network, for example, the voltage is constant. And with a finger battery it is constant. The difference is simple - a constant voltage has a plus and a minus - an alternating one does not. Why not? Everything is very simple. In a network with alternating voltage, plus and minus constantly change places. The same contact is either a plus or a minus. How often? But for this, there is another value - 50 Hz. What is Hz? This is one oscillation per second. That is, in our home network, plus changes with minus fifty times a second. And now - what is the practical use of this knowledge, what does it have to do with the LED? Let's figure it out. Suppose you have a 220 volt 100 watt light bulb in your hands. If you plug it into the electrical network, it will light up with all its hundred watts. And if we do not need these 100 watts? Do you need, say, 50 watts? DIOD will help us with this.
If you break the word Light-emitting diode" into components, then we get " light" and " diode". That is, it is an ordinary diode that also glows. A diode is a device that is best compared, for example, with a valve or a nipple in a car wheel. You can pump air in there, but the nipple does not let it back in. An ordinary diode looks like a black barrel with two leads - plus and minus.So we can use it for practical experiments, which help many to consolidate the material.Of course, it is dangerous to start experiments immediately with 220 volts, but with due care nothing bad will happen.Nevertheless, everything you conduct experiments at your own peril and risk :) We need a light bulb from a refrigerator for 220v, 15 W. For it, we need to find a suitable cartridge and remove two wires from it.Then we need any diode that can be obtained, for example, from any faulty TV or a tape recorder. The larger it is, the better. You don’t need to take very small ones - 220 volts, after all. Near it, there is usually a designation in the form of a triangle.
Then we need a power cord with a plug, some wires and a soldering iron. To get started, just connect the light bulb to the network and remember how it glows. Then disconnect and assemble the circuit according to the diagram on the left. Do not forget to carefully insulate all connections with electrical tape. Plug in. As you can see, the light bulb shines much worse. This is not surprising - she now receives only half the voltage she needs - the second diode does not let go. If your experience was successful, and the diode is large enough, you can now make any of your light bulbs practically eternal. For example, a 50-watt lamp shines in your hallway and constantly burns out. Take a 100 watt, turn it on through a diode - it will shine like about 50 watts, but it will not burn out. There is, however, one caveat - the diode must be designed for a voltage of 350-400 volts and a current of at least an ampere. It is best to buy one at a radio parts store.
Well, since we figured out what a diode is, it makes sense to move on to the topic of interest to us - LED. The LED, as it is now clear, also has a plus and a minus. That is, for its operation, you need a source of constant voltage - a battery, a battery, a power supply. The power supply must be labeled as supplying direct voltage (DC). Usually on the cover of the block there is a sticker of this content.
Input - ~220V 50HZ,
output - 12v, 0.5A DC
This means that such a unit can produce a constant voltage of 12 volts and a current of 0.5 amperes.
Note that a cell phone charger is also a power supply. It usually has parameters of 5-6 volts, 0.2-0.5 A. It is often very convenient to use it to power LEDs, because the charger stabilizes the current. But more on that later in future articles.
Two parameters are important to us - the operating voltage of the LED and the current. The operating voltage of an LED is also called "voltage drop". In essence, this term means that after the LED, the voltage in the circuit will be less by the size of this very drop. That is, if we supply power to Light-emitting diode, which has a voltage drop of 3 volts, then it will eat these three volts, and the device connected after it to the same circuit will get 3 volts less. But the most important thing to learn is that the current is important to the LED, not the voltage. He will take as much voltage as he needs, but as much current as you give. That is, if your power supply can deliver 10 amps, the LED will take current until it burns out. The logic here is simple - the connected LED consumes current and starts to warm up. The more it heats up - the more current can pass through it - it expands from heating. As the current increases, the voltage drop across the diode increases. And so on until it burns out completely - no one has limited the current. And this must be done using a bounding element.
Note that if the power supply has an output voltage equal to the operating voltage of the LED, it is not necessary to limit the current. That is, if you have, for example, a white LED and a 3.6 volt battery from a cell phone - you can connect it directly to this battery - nothing will happen to the LED. He would be glad to grab more current - but there is not enough voltage. So a 3.6V cell phone battery is the perfect power source for experimenting with white and blue LEDs. Why only with them - about this in other articles.
In general, in series with the LED, we need to put a kind of tap and twist it to the value we need. Various devices can act as such a crane. The simplest of them is a resistor. How to correctly limit LED current says in my article. And we will go further. True, if you are not interested in how the LED works, but just want to learn about its practical application, it is better to go to the end of the page and select another part "For dummies". But if you are determined to learn about solid-state light sources "from the very beginning" - let's continue our acquaintance;)
Optical aspects of the use of LEDs
"There is enough light for those who want to see, and enough darkness for those who don't"
B. PascalSuppose we have learned to connect Light-emitting diode and limit its current. The question arises - how much does it shine? Here we have to plunge a little into optics.
Among the properties of LEDs, especially powerful ones, the type of light distribution is often indicated. This is usually the so-called Lambertov
sky chart. Further we will consider it as the most common. What does this term mean? "Lambertovsky" LED shines in all directions equally, regardless of direction. If the LED were a ball, it would shine the same way in all directions - this is the essence of the Lambert diagram. To be clear, the sun is a Lambertian source. The standard LED design is a crystal, a thin plate that glows. Look into the transparent window of the LED - and you will see this crystal. To him are thin wires of contacts. If you connect your imagination, you can imagine the light coming from the LED as a spherical cloud hanging above it. Light is small particles called photons. This means that a ball filled with photons hangs above the LED. And the more light the LED emits - the larger the ball, the farther the photons fly, pushing and displacing each other. Most of them fly upwards perpendicular to the plane of the crystal, so the maximum luminous intensity of the LEDs is 90 degrees relative to the horizontal axis. I hope that now the diagrams given by LED manufacturers have become more understandable to you :) To make it completely clear, let's look at an example. 
Let's accept that there is Light-emitting diode, at the top of which hangs a light sphere emitted by it with a diameter of 1 meter (nice LED! :)). The lower scale is the distance to the top of this meter, the upper one is the degree of radiation. In accordance with this diagram, most photons are on the axis with degree 0. The further the deviation from the axis and the greater the distance from the crystal, the lower the density of photons. We must also not forget that light is a wave, it is not in vain that the wavelength is indicated for the characteristics. Accordingly, our light sphere can be represented as an electromagnetic field with a certain density. But this is already wilds - let's move on :)
Half brightness angle
The manufacturer usually specifies a parameter such as double angle half brightness. What does this term mean? As we found out, the LED gives maximum light in the center, that is, the angle is zero. Accordingly, the farther from the center, the less light. The half brightness angle is when at "0" degrees the LED gives 100 arbitrary units of light, and, for example, at 30 degrees (relative to the "0" axis) - 50.
In the figure, I is the luminous intensity, Imax is the maximum luminous intensity. ImaxCos - half the strength of the light. Why "double" - we multiply the degrees by two, the LED shines symmetrically. As a result, we get a nice isosceles triangle of light. There is also light outside of this triangle, but the reference point for the LED characteristic is the half angle. Candela
Now we can consider what is Candela. Candela is, according to the old, "candle". Remember, they used to say - a chandelier or a lamp of a hundred candles? In the old days, some kind of reference point was needed. We agreed to take a candle of the required thickness, light it and consider it a standard, this same candela. In our times, of course, they think differently. I will not explain in detail - how, this is already beyond the scope of the article. There is simply a unit of measure for the intensity of light, and it is called the candela. Its main feature is the use to measure the intensity of light directed sources. That's why for 5mm LEDs the values are given in candelas, more precisely millicandelas (1 cd=1000 mcd).It's time to figure out how 5 mm LEDs or any other LEDs in a plastic case differ from powerful ones.
Design features of indicator 5 mm LEDs
As mentioned above, Light-emitting diode is a crystal that emits light. Consider the design of the LED in a 5 mm plastic case. On closer examination, we find two important things - lens and reflector. In reflector
the LED crystal is placed. This reflector sets the initial scattering angle. The light then passes through the epoxy resin housing. It reaches the lens - and then it begins to scatter on the sides at an angle that depends on the design of the lens. In practice - from 5 to 160 degrees. To indicate the luminous intensity of such LEDs, it is just used candela. Directional LEDs emit light over a certain solid angle. To understand what a solid angle is, it is enough to imagine the following picture. You take a flashlight, turn it on and place it in the fire bucket at the very bottom, then close the lid. The light inside, respectively, has the form of a three-dimensional cone in the shape of our bucket. This cone, bounded by a lid, is the solid angle. I will try to explain the meaning of the distribution of light in a simpler way. Let's say the light intensity of our lantern is 1 candela, that is, 1000 millikandel(to make it more figurative, we can consider millicandels as photons :)) If we continue by analogy, we have a full bucket of millicandels. The volume of the bucket can be calculated if desired - welcome to geometry :) Accordingly, if we take a bucket twice as large, the millicandels will be evenly distributed over it, that is, there will be no more of them, the density will simply decrease. Therefore, do not chase after candela when choosing an LED - the wider its angle, the less candela - the same one. In all these explanations, you can find the answer to the sacred question - how many LEDs do you need to replace a hundred-watt light bulb. More on this later. Design features of high-power LEDs
Unlike indicator LEDs, powerful ones are not only a device, but also a marketing product. Today, there is a real race for lumens between large manufacturers - who is more? And no one cares that these lumens still need to be applied. Let's go in order.The main difference between a high-power LED and an indicator LED in its pure form is the minimization of any obstacles for light to escape from the LED housing. So high power LEDs have a Lambert diagram. What does this lead to in practice? You turn on an LED and you get a nice little ball of light above it. And what to do next? How do they illuminate the surface you need? Obviously, you need to make the radiation angle narrower. You have to use different optics or reflectors, which inevitably leads to losses, and therefore a decrease in the luminous flux. Therefore, if, having bought a powerful LED, you have not acquired good optics, moreover, designed specifically for its design, you rejoice early - the headache is yet to come. Delivering the lumens you need to the surface you need to illuminate is no easy task. However, if you just need to illuminate the room - you can do without optics - a diffuser is enough.
Lumen
Suite
Suite is the ratio of the number of lumens to the illuminated area. 1 lux is 1 lumen per square meter. Let's say we have a square surface of one meter. All of it is evenly illuminated by a light bulb located at some distance vertically from above. For this light bulb, the manufacturer stated the illumination of 100 lux. We take a device called a luxmeter and measure it at any point in our square, we should get 100 lux. If so, the manufacturer did not deceive us. This applies to a light source that shines equally in all directions (Lambertian source). But the LED has the greatest luminous intensity on an axis perpendicular to the plane of the crystal. In other words, by hanging the LED on the ceiling and measuring it with a luxmeter, we will see that the farther from the axis, the lower the reading of the device. All of you have probably come across spotlight incandescent lamps - these are the so-called "reflex cameras". The back of the bulb of these lamps is covered with a mirror composition, and they only shine downwards. Here is an analogue for you.Features of the practical application of LEDs - in the next article.
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