What are lumens and how to convert them to watts? Comparison of light from different sources

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 of 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. Compact fluorescent lamp daylight with a power of 26 W creates a luminous flux equal to approximately 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:

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Luminous flux of lamps (lm)

big LED-high, big LED-med, big LED-low, 5 MM - High, 5 MM - medium, 5 MM - low

Disputes on the topic of comparing the luminous flux of diode and other types of lamps constantly arise on the vast expanses of the Internet. This is due to the uniqueness technical parameters LEDs as a light source, namely the specifics of point sources.

All light sources, whether incandescent or fluorescent, have a circular light scattering pattern, when the LED has a beam with a scattering angle of about 120 0. Therefore, the lighting characteristics of the diode depend on the angle from which they are evaluated.

Comparison of light from different sources

For example, often on the packaging of 4W LEDs with a luminous flux of 400 lm, a 50W incandescent lamp is depicted as the equivalent. In fact, the total luminous flux of the second is almost a quarter higher.

But if you compare effective illumination of the table surface from a table lamp with an ordinary lamp and diodes, the advantage is on the side of LED, since they have a smaller light spot diameter and significantly less light scattering.

The scatter of the parameters of the light flux is due to its dependence on the color temperature. Cool white light diodes (color temperature 5000-7000 K) have a higher luminous flux than warm light LEDs (2800-3500 K).

Let's look at this information from a practical point of view.

When choosing an ordinary incandescent bulb, we intuitively understand that 75 watts are needed in the bathroom, 60 watts can be dispensed with in the corridor, and three hundred watts will have to be screwed into the living room. And no one wonders how many lumens there are in them.

What are lumens in LED lamps

With the transition to LED, the concept of brightness and illumination has to be considered from a completely different angle. As can be seen from the tables, the power of LEDs when replacing an incandescent lamp should be about ten times less. But here it is necessary to take into account special purpose lighting.

When it comes to room lighting, 100 watt incandescent bulbs produce as many lumens as 10 watt LEDs. With one caveat - products of a radial design are used as a diode bulb. As shown.

Work surface lighting

Flat LED modules are used to illuminate work surfaces, since there is no reason to illuminate the inner surface of the ceiling.

In such a system, the effective incandescent brightness does not exceed 60% of the nominal value. The net luminous flux from 60W will be about 350 lumens (630 * 0.6). But the efficiency of LEDs in such a system is almost 100%.

Accordingly, the calculated power of the LEDs will not exceed 5W.

Illumination and luminous flux

For the average consumer, it is not so important how many lux the light source produces. It is more important that at this level of illumination it would be comfortable for the eyesight when reading or writing.

All sanitary rules standardize the lighting of the work surface in lux. Whether it is a page of a book or a sheet of paper, for comfortable work on their surface there should be 300 lux, which corresponds to 30lm/sq.m.

How many lumens in a 100W incandescent lamp is important, for example, for organizing a child's workplace, where he will do homework or do other things.

It is extremely difficult to calculate the illumination of a surface, even knowing how many lumens there are in a 100W light bulb, since most of this flux comes in the form of reflected light. For diodes, an elementary formula from a school geometry course is enough.

H– distance from the LEDs to the surface;

D is the diameter of the light spot;

D = 2 * Tg60 0 * h = 1.16 * h;

Circle area \u003d 3.14 * D 2 / 4 \u003d 0.785 * D * D;

Illumination \u003d luminous flux / area of ​​\u200b\u200bthe circle.

In total: a 15W LED light source with a luminous flux of 800lm, placed on the ceiling above the table, will provide about 300 lux.

The figure below indicates where the properties of the light flux from the source appear, corresponding to the units of measurement - lumens, candela and lux.

Lumen, unlike candelas and lux, less commonly used units, is a measure of the total amount of light coming from a source, the so-called. ‘luminous flux’. Something like horsepower in an engine. It's actually quite a general metric because it doesn't rely on a standardized unit of measure to compare it to. The measure in lumens does not take into account the presence of a reflector and lens in the flashlight, the type of surface of the reflector, therefore, cannot serve as a description of the practical brightness of the flashlight, or its useful performance.

Candela, ‘power of light’, would be a better description of lanterns, especially used as an everyday tool. It shows how bright a light source is relative to how far it can be seen. If you use the comparison with the engine again, it's like torque.

One candela- it's like one burning candle, the intensity of the glow of which in theory does not change, even if a barrier is placed on the light, and remains constant when viewed from different angles at the same distance. In the sense that if you look at a candle from any angle at a distance of 20 meters, its brightness will be constant. So the candela is not only a descriptive characteristic, it is a real measure of the flashlight's capabilities.

Also candela refers to the measurement of a focused beam of light, while lumens refers to the total amount of light emitted. One lumen is equal to the luminous flux emitted by a source with a luminous intensity equal to one candela - this is in a deliberately simplified form without important details.

Suite on the other hand, ‘illuminance’ is a measure of the amount of light falling on the surface of a given area. Lux is equal to the illumination of a surface of 1 sq. m. with a luminous flux of radiation falling on it, equal to 1 lumen. So this measure is relative to the surface you intend to illuminate.

If it's still too complicated, then let's draw a line: compare lumens to lumens, and candela to candela. If you are comparing two different products described by different units of measurement, then calculate the ratio, the Internet is full of calculators and tables.

The choice of units in which the flashlight is rated depends on how you intend to use the flashlight. If you want to illuminate an area with flood light, then such a flashlight is best priced in lumens. Candela is better suited for concentrated beam characterization, like a searchlight. One is suitable for illuminating spaces and inspecting rooms, the other for individual illumination of targets.

In addition to being distinguished different units measurements, it is important to understand that more is not necessarily better. One of the reasons for this is the limited field of view of a person, and when you illuminate a space larger than your vision and consciousness can process, this is hardly beneficial. Such highlighting can give you away, or highlight someone you'd rather not highlight. When examining a room, you need to illuminate it, but you do not need rays of light to break through the cracks into the street. until you find the bad guy.

There are additional considerations when deciding which flashlight to invest in. And buying a strong, reliable flashlight is a serious investment. If you choose by price and appearance, and not having studied the experience of users - it is easy to miscalculate. Well-known manufacturers with a good reputation provide the best warranty, service, and ultimately performance, but the name of the company alone should not be decisive.

For this category of equipment there is a rule: " Two is one, and one is nothing!". Even if you have a spare battery or a spare light bulb, chances are your main light will have problems and you will need to use a spare. Fellows get very annoyed when you constantly borrow from them.

There is a lot of debate about which type of battery is better. If you don't change the battery (or charge the battery) before every outing, you need a spare light.

The photo below shows batteries of standard sizes: 10430 (similar to AAA battery), 14500 (similar to AA battery), 16340 (similar to CR123 battery), 18650, 26500 (similar to C battery):

Test your flashlight before you walk out the door, it will save you a lot of headaches. Additional options may include adjustable focus, strobe, and different types light sources. Some flashlights change modes with a few clicks on one button.

While the adjustable focus may come in handy for site inspections, rescue missions, and so on, the reality of high-intensity combat will prevent this feature from being used. The same applies to switching modes with a tricky combination of short and long presses on the button.

Most of the people I know prefer not to rely on fine motor skills when under stress. Such manipulations, with precisely calibrated multiple clicks, are very difficult to practice.

In general, a lot of nuances affect the effectiveness of the flashlight. In recent years, there has been a leap in the technology of lenses and light sources. After a quick and easy replacement of the light module, the old lamp is literally transformed, becoming modern, powerful and economical.

No less important, in addition to having a good flashlight, is also. The use of a flashlight on a weapon, together with a weapon, and everyday needs make this issue very relevant, so training is the key to success.

And - an occupation that requires a fair amount of enlightenment. Shine up! =)

Ten years ago, choosing the right light bulb was easier, because incandescent bulbs were marked with maximum power. Currently, new LED-lamps are gaining more and more popularity. It is more difficult to choose a product of the required power in the modern era of lighting, because LED lamps, compact fluorescent lamps and others energy-saving lamps completely changed the power values. Now it will not be entirely correct to focus on watts, and it is not always possible. If in a regular store a specialist can still help you choose the right light bulb, then when making a purchase via the Internet, you are unlikely to find a watt in the description of this light bulb.

What is luminous flux?

Watts refer to the amount of energy consumed. For example, a 100W light bulb uses more energy than a 60W light bulb. This value indicates how much energy will be spent - it does not indicate the amount of light rays that the lamp gives. How much light you get from a light bulb shows 1 lumen.

Lumen is a unit of measurement luminous flux in the system of calculus. The brighter the light bulb, the larger this value will be. For example, a conventional 40 W incandescent lamp has a luminous flux of 300 lumens. Converting lumens to watts is not as easy as it seems.

The packaging of each product must contain information about how much light this product gives. When electrical energy is converted into light rays, some of it is lost and therefore large values ​​are not achieved. It can be seen that this figure for incandescent lamps is 12 lumens per watt, while fluorescent lamps give 60 lumens per watt. LED lamps provide maximum illumination with minimum energy consumption - up to 90 lumens per watt.

Using this approach, it is not always possible to get the right results, because even bulbs of the same type with the same power can have a different ratio of luminous flux to energy costs, and the difference can be quite significant. Below is a table that allows you to convert watts to lumens for a lamp on first use. With its help, you can easily find out how many lumens are in an incandescent lamp, for example.

It follows from the table that a 600 lm LED lamp is not the equivalent of a 60 W incandescent lamp, and 1,000 lm is not the equivalent of a 100 W incandescent lamp.

Parameters that determine the luminous flux and its calculation

The beam consists of a stream of particles - photons. When these particles enter a person's eyes, certain visual sensations arise. The more photons hit the retina in a certain period of time, the more illuminated the object seems to us. Thus, the lamps emit a luminous flux of photons, which, falling into the eyes, allow us to clearly see objects in front of us.

Unfortunately, the longer the light bulb is used, the less brightness it can give. The lamp itself can also worsen the illumination indicator, because often the losses depend on the quality of the lamp material. The largest losses of luminous flux are observed in gas-discharge sources; for fluorescent lamps, these losses can be 20–30%, for incandescent lamps, 10–15%. LED lamps have the highest light output - light loss is less than 5%.

To convert the luminous flux of a lamp to lumens, use the average light output values:

• for diode products, multiply the power by 80–90 lm / W for light bulbs with a frosted bulb and get the light flux;
• for diode filaments (transparent products with yellow stripes) multiply the power consumption by 100 lm/W;
• multiply fluorescent energy-saving lamps by 60 lm / watt;
• for a HPS lamp, this value will be 66 lm / W for 70W; 74 lm/w for 100W, 150W, 250W; 88 lm/w at 400W;
• for an arc mercury lamp, the multiplier will be 58 lm / W;
• a 100 W incandescent lamp produces approximately 1,200 lumens. If the power is reduced to 40 W, the flux will reach 400 lm. But a 60 watt light bulb has an indicator of about 800 lm.

If you need to accurately determine the luminous flux, you will need a luxmeter device. It can be used to calculate , what luminous flux will be at the selected points of the room according to a known method.

One lux corresponds to a certain luminous flux falling on an illuminated surface of one square meter. You can determine the approximate value of the luminous flux created by a particular source using the formula:

F \u003d E x S,
where S is the area of ​​all surfaces of the room you are examining (in square meters), and E is the illumination (in lux).

So if the surface area is 75 sq. meters, and the illumination is 40 lux, the luminous flux is 3,000 lumens. To accurately calculate the luminous flux, many other spatial factors will have to be taken into account.

If you choose the right LED lamp in all respects, subject to all the requirements of the manufacturer, it is guaranteed to last for many years. Currently, the least energy-consuming and most illuminating products are not cheap, but over time they will become available to all consumers.

A lot of myths arise around the concept of "lumen", therefore, in order to dispel some of them, we will consider the most frequently asked questions, such as: how many lumens in an incandescent lamp, in an LED lamp, how many lumens does 1W contain led lamp how to determine its luminous flux, and which LED lamps are similar to incandescent lamps.

To begin with, let's figure out what the concept of "lumen" means. A lumen is a unit of measure for the amount of light emitted from a light source, which can be an incandescent lamp, LED lamp, LED, or other lighting fixture.

To make it easier to comparative analysis, you can refer to the table, which shows the ratio of SP (lumens) to the power of the lighting device (W) for incandescent, fluorescent and LED lamps. Based on these data, it can be seen that LED lamps are 10 times more efficient than incandescent lamps, and 2 times more efficient than fluorescent lamps. In addition, unlike fluorescent lamps and incandescent lamps, the LED lamp, and therefore the LED, emits directional light, from which it can be concluded that the illumination from the LED lamp will be much higher. Therefore, using an LED street lamp as lighting, you can achieve much better illumination than when using other lamps.

As for the number of lumens in a 1W LED lamp.

For LEDs, the luminous flux ranges from 80 to 150 lm out of 1 watt. This is due to some differences in the current-voltage characteristics of LEDs and cooling systems. The luminous flux of experimental LEDs reaches 220 lm / W, but such LEDs are not found in mass production.

How can you determine the number of lumens in a lamp or light bulb.

Usually this information is indicated on the packaging or in the instructions for the product, but tabular data can also be used.
To independently determine lumens, you need a luxmeter that determines the level of illumination in each area of ​​\u200b\u200bthe room. Lux in this case is the quantitative ratio of lumens to the area of ​​illumination (1lux-1lumen per m2). With the intensity of light coming from an isotropic source equal to 1 candela, the total luminous flux is 4