Length and Distance Converter Mass Converter Bulk and Food Volume Converter Area Converter Volume and Units Converter culinary recipes Temperature Converter Pressure, Mechanical Stress, Young's Modulus Converter Energy and Work Converter Power Converter Force Converter Time Converter Linear Velocity Converter Flat Angle Thermal Efficiency and Fuel Efficiency Converter Various Numeric Systems Converter Information Unit Converter Currency Rates Women's Clothing and Shoes Sizes Sizes men's clothing and footwear Angular Velocity and Rotation Rate Converter Acceleration Converter Angular Acceleration Converter Density Converter Specific Volume Converter Moment of Inertia Converter Moment of Force Converter Torque Converter Specific Heat of Combustion (by Mass) Converter Energy Density and Heat of Combustion (by Volume) Converter Converter Temperature Difference Coefficient of Thermal Expansion Converter Thermal Resistance Converter Thermal Conductivity Converter Specific Heat Capacitance Converter Energy Exposure and Power Converter Te heat flux heat flux density converter heat transfer coefficient converter volumetric flow rate mass flow rate molar flow rate mass flux density converter molar concentration converter mass concentration in solution dynamic (absolute) viscosity converter kinematic viscosity converter surface tension converter vapor permeability and vapor transfer rate converter Sound level converter Microphone sensitivity converter Sound pressure level (SPL) converter Sound pressure level converter with selectable reference pressure Luminance converter Luminous intensity converter Illumination converter Computer graphics resolution converter Frequency and wavelength converter Optical power in diopters and focal length Optical power in diopters and lens magnification (×) Converter electric charge Linear Charge Density Converter Surface Charge Density Converter Bulk Charge Density Converter Converter electric current Linear Current Density Converter Surface Current Density Electric Field Strength Converter Electrostatic Potential and Voltage Converter Electrical Resistance Converter Electrical Resistivity Converter Electrical Conductivity Converter Electrical Conductivity Converter Electrical Capacitance Inductance Converter American Wire Gauge Converter Levels in dBm (dBm or dBmW), dBV ( dBV), watts and other units Magnetomotive force converter Magnetic field strength converter Magnetic flux converter Magnetic induction converter Radiation. Ionizing Radiation Absorbed Dose Rate Converter Radioactivity. Radioactive Decay Radiation Converter. Exposure Dose Converter Radiation. Absorbed Dose Converter Decimal Prefix Converter Data Transfer Typography and Image Processing Unit Converter Timber Volume Unit Converter Molar Mass Calculation Periodic system chemical elements D.I. Mendeleev

1 lux [lx] = 0.0929030400000839 lumens per sq. ft [lm / ft²]

Initial value

Converted value

lux meter-candela centimeter-candela foot-candela phot nox candela-steradian per sq. meter lumens per sq. meter lumens per sq. centimeter lumens per sq. foot watt per sq. cm (at 555 nm)

Linear charge density

More about illumination

General information

Illuminance is a luminous quantity that determines the amount of light that hits a given area of ​​the body's surface. It depends on the wavelength of light, since the human eye perceives the brightness of light waves of different lengths, that is, different colors, in different ways. Illuminance is calculated separately for different wavelengths, since people perceive light with a wavelength of 550 nanometers (green), and colors that are nearby in the spectrum (yellow and orange), as the brightest. Light generated by longer or shorter wavelengths (violet, blue, red) is perceived as darker. Illumination is often associated with the concept of brightness.

Illumination is inversely proportional to the area over which the light falls. That is, when illuminating the surface with the same lamp, the illumination of a larger area will be less than the illumination of a smaller area.

Difference between brightness and illumination

Brightness Illumination

In Russian, the word "brightness" has two meanings. Brightness can mean a physical quantity, that is, a characteristic of luminous bodies equal to the ratio of the intensity of light in a certain direction to the area of ​​the projection of the luminous surface onto a plane perpendicular to this direction. It can also define a more subjective concept of overall brightness, which depends on many factors, such as the characteristics of the eyes of the person who is looking at this light, or the amount of light in the environment. The less light around you, the brighter the light source appears. In order not to confuse these two concepts with illumination, it is worth remembering that:

brightness characterizes light, reflected from the surface of a luminous body or sent by this surface;

illumination characterizes falling light onto the illuminated surface.

In astronomy, brightness characterizes both the emitting (stars) and reflective (planets) ability of the surface of celestial bodies and is measured on the photometric scale of stellar brightness. Moreover, the brighter the star, the lower the value of its photometric brightness. The brightest stars have negative stellar brightness.

Units

Illumination is most often measured in SI units. suites... One lux equals one lumen per square meter. Those who prefer imperial units to metric units use to measure illumination foot candela... It is often used in photography and cinema, as well as in some other areas. The foot is used in the name because one foot-candela denotes the illumination of one candela of a surface of one square foot, which is measured at a distance of one foot (a little over 30 cm).

Photometer

A photometer is a device that measures illumination. Usually the light is sent to a photo detector, converted into an electrical signal and measured. Sometimes there are photometers that work on a different principle. Most photometers provide lux information, although other units are sometimes used. Photometers, called exposure meters, help photographers and operators determine shutter speed and aperture. In addition, photometers are used to determine safe illumination in the workplace, in crop production, in museums, and in many other industries where it is necessary to know and maintain a certain illumination.

Illumination and safety in the workplace

Working in a dark room can lead to visual impairment, depression, and other physiological and psychological problems. That is why many labor protection rules include requirements for minimum safe illumination of the workplace. Measurements are usually carried out with a photometer, which gives the final result depending on the area of ​​propagation of the light. This is necessary in order to provide sufficient illumination throughout the room.

Illumination in photo and video shooting

Most modern cameras have built-in exposure meters to simplify the work of the photographer or operator. A light meter is necessary so that the photographer or operator can determine how much light needs to be transmitted onto the film or photomatrix, depending on the illumination of the object being shot. Illumination in lux is converted by the exposure meter into possible combinations of shutter speed and aperture, which are then selected manually or automatically, depending on how the camera is configured. Usually the combinations suggested depend on the settings in the camera and what the photographer or cameraman wants to portray. In the studio and on set, an external or in-camera light meter is often used to determine if the light sources being used are providing sufficient lighting.

To receive good photos or video material in poor lighting conditions, a sufficient amount of light must enter the film or sensor. This is not difficult to achieve with a camera - you just need to set the correct exposure. The situation with video cameras is more complicated. For high quality video, you usually need to install additional lighting, otherwise the video will be too dark or with a lot of digital noise. This is not always possible. Some camcorders are specially designed for shooting in low light conditions.

Cameras designed for shooting in low light conditions

There are two types of cameras for shooting in low light conditions: some use more optics than high level while others have more advanced electronics. The optics let more light into the lens, and the electronics are better at processing even the smallest light that enters the camera. It is usually with electronics that the problems and side effects described below are associated. High-aperture optics allow you to shoot video of higher quality, but its disadvantages are additional weight due to a large number glass and a significantly higher price.

In addition, the quality of shooting is influenced by the single-matrix or three-matrix photo matrix installed in video and still cameras. In a three-matrix matrix, all incoming light is divided by a prism into three colors - red, green and blue. Image quality in dark conditions is better in three-array cameras than in single-array cameras, since less light is scattered when passing through a prism than when it is processed by a filter in a single-array camera.

There are two main types of photo matrices - charge-coupled devices (CCDs) and made on the basis of CMOS technology (complementary metal oxide semiconductor). In the first, a sensor is usually installed, which receives light, and a processor that processes the image. In CMOS sensors, the sensor and processor are usually combined. In low light conditions, CCD cameras usually provide an image best quality, and the advantages of CMOS matrices are that they are cheaper and consume less power.

The size of the image sensor also affects the image quality. If shooting takes place with a small amount of light, then the larger the matrix, the better quality image, and the smaller the matrix, the more problems with the image - digital noise appears on it. Larger sensors are installed in more expensive cameras, and they require more powerful (and, as a result, heavier) optics. Cameras with such matrices allow you to shoot professional video. For example, recently a number of films have appeared entirely shot on cameras such as the Canon 5D Mark II or Mark III, which have a matrix size of 24 x 36 mm.

Manufacturers usually indicate in what minimum conditions the camera can operate, for example, with an illumination of 2 lux or more. This information is not standardized, that is, the manufacturer decides for himself which video is considered to be of high quality. Sometimes two cameras with the same minimum illumination will give different quality shooting. The EIA (Electronic Industries Association) in the United States has proposed a standardized system for determining the sensitivity of cameras, but so far it is used only by a few manufacturers and is not universally accepted. Therefore, often, in order to compare two cameras with the same light characteristics, you need to try them in action.

On this moment any camera, even one designed for low light conditions, can produce poor quality images with high graininess and afterglow. To solve some of these problems, it is possible to take the following steps:

• Shoot on a tripod;
• Work in manual mode;
• Do not use variable focal length mode, but instead move the camera as close to the subject as possible;
• Do not use auto focus and auto ISO selection - higher ISO values ​​increase noise;
• Shoot with a shutter speed of 1/30;
• Use diffused light;
• If it is not possible to install additional lighting, then use all possible light around, such as street lamps and moonlight.

Despite the lack of standardization about the sensitivity of cameras to light, for night photography it is still better to choose a camera that says it works at 2 lux or lower. Also keep in mind that even though the camera is really good at shooting in dark conditions, its Lux sensitivity to illumination is the sensitivity to light directed at an object, but the camera actually receives light reflected from the object. When reflected, part of the light is scattered, and the further the camera is from the object, the less light enters the lens, which degrades the quality of shooting.

Exposition number

Exposition number(English Exposure Value, EV) - an integer characterizing possible combinations excerpts and diaphragms in a photo, film or video camera. All combinations of shutter speed and aperture, in which the same amount of light falls on the film or photosensitive matrix, have the same exposure number.

Several combinations of shutter speed and aperture in the camera at the same exposure number allow you to get approximately the same image density. However, the images will be different. This is due to the fact that at different aperture values, the depth of field will be different; at different shutter speeds, the image on the film or matrix will remain for different times, as a result of which it will be blurred to varying degrees or not at all. For example, combinations of f / 22 - 1/30 and f / 2.8 - 1/2000 are characterized by the same exposure number, but the first image will have a greater depth of field and may be blurry, and the second will have a shallow depth of field and, quite possibly will not be blurry at all.

Higher EV values ​​are used when the subject is better lit. For example, an exposure value (at ISO 100) EV100 = 13 can be used when shooting a landscape if the sky is cloudy, and EV100 = –4 is suitable for shooting a bright aurora.

A-priory,

EV = log 2 ( N 2 /t)

2 EV = N 2 /t, (1)

where
• N- f-number (for example: 2; 2.8; 4; 5.6, etc.)
• t- shutter speed in seconds (for example: 30, 4, 2, 1, 1/2, 1/4, 1/30, 1/100, etc.)

For example, for a combination of f / 2 and 1/30, the exposure value is

EV = log 2 (2 2 / (1/30)) = log 2 (2 2 × 30) = 6.9 ≈ 7.

This number can be used for night scenes and illuminated shop windows. A combination of f / 5.6 with a shutter speed of 1/250 gives an exposure value

EV = log 2 (5.6 2 / (1/250)) = log 2 (5.6 2 × 250) = log 2 (7840) = 12.93 ≈ 13,

which can be used to capture a landscape with a cloudy sky and no shadows.

It should be noted that the argument of the logarithmic function must be dimensionless. In determining the exposure value EV, the dimension of the denominator in formula (1) is ignored and only the numerical value of the shutter speed in seconds is used.

The relationship of the exposure number with the brightness and illumination of the subject

Determining the exposure by the brightness of the light reflected from the subject

When using exposure meters or lux meters that measure the light reflected from the subject, shutter speed and aperture are related to the brightness of the subject as follows:

N 2 /t = LS/K (2)

• N- f-number;
• t- exposure in seconds;
• L- average scene brightness in candelas per square meter (cd / m²);
• S- arithmetic value of photosensitivity (100, 200, 400, etc.);
• K- calibration factor of the exposure meter or lux meter for reflected light; Canon and Nikon use K = 12.5.

From equations (1) and (2) we obtain the exposure number

EV = log 2 ( LS/K)

2 EV = LS/K

At K= 12.5 and ISO 100, we have the following equation for brightness:

2 EV = 100 L/12.5 = 8L

L= 2 EV / 8 = 2 EV / 2 3 = 2 EV – 3.

Illumination and museum exhibits

The rate at which museum exhibits decay, fade and otherwise deteriorate depends on their illumination and on the strength of the light sources. Museum staff measure the illumination of exhibits to make sure that a safe amount of light is entering the exhibits, and also to provide enough light for visitors to get a good look at the exhibit. Illumination can be measured with a photometer, but in many cases it is not easy, since it must be as close to the exhibit as possible, and for this it is often necessary to remove safety glass and turn off the alarm, as well as obtain permission to do so. To facilitate the task, museum workers often use cameras as photometers. Of course this is not a substitute accurate measurements in a situation where a problem is found with the amount of light that enters the exhibit. But in order to check whether a more serious check with a photometer is needed, a camera is enough.

The exposure is determined by the camera based on the light readings, and knowing the exposure, you can find the light with a few simple calculations. In this case, museum staff use either a formula or a table with the conversion of exposure into light units. During calculations, do not forget that the camera absorbs part of the light, and take this into account in the final result.

Illumination in other areas of activity

Gardeners and plant breeders know that plants need light for photosynthesis, and they know how much light each plant needs. They measure light in greenhouses, orchards and vegetable gardens to make sure each plant is getting enough light. Some people use photometers for this.

Do you find it difficult to translate a unit of measurement from one language to another? Colleagues are ready to help you. Post a question to TCTerms and you will receive an answer within a few minutes.

Length and Distance Converter Mass Converter Bulk and Food Volume Converter Area Converter Culinary Recipe Volume and Units Converter Temperature Converter Pressure, Stress, Young's Modulus Converter Energy and Work Converter Power Converter Force Converter Time Converter Linear Velocity Converter Flat Angle Converter Thermal Efficiency and Fuel Efficiency Numeric Conversion Systems Converter of Information Measurement Systems Currency Rates Women's Clothing and Shoes Sizes Men's Clothing and Shoes Sizes Angular Velocity and Rotational Speed ​​Converter Acceleration Converter Angular Acceleration Converter Density Converter Specific Volume Converter Moment of Inertia Converter Moment of Force Torque converter Specific calorific value (mass) converter Energy density and specific calorific value (volume) converter Temperature difference converter Coefficient converter Thermal Expansion Curve Thermal Resistance Converter Thermal Conductivity Converter Specific Heat Capacity Converter Thermal Exposure and Radiation Power Converter Heat Flux Density Converter Heat Transfer Coefficient Converter Volumetric Flow Rate Converter Mass Flow Rate Converter Molar Flow Rate Converter Mass Flux Density Converter Molar Concentration Converter Mass Concentration in Solution Converter absolute) viscosity Kinematic viscosity converter Surface tension converter Vapor permeability converter Vapor permeability and vapor transfer rate converter Sound level converter Microphone sensitivity converter Sound pressure level (SPL) converter Sound pressure level converter with selectable reference pressure Luminance converter Luminous intensity converter Light intensity converter Resolution to computer converter chart Frequency and wavelength converter Optical power to diopter x and focal length Optical power in diopters and lens magnification (×) Electric charge converter Linear charge density converter Surface charge density converter Bulk charge density converter Electric current linear current density converter Surface current density converter Electric field strength converter Electrostatic potential and voltage converter Converter Electrical Resistivity Electrical Resistivity Converter Electrical Conductivity Converter Electrical Conductivity Converter Electrical Capacitance Inductance Converter American Wire Gauge Converter Levels in dBm (dBm or dBmW), dBV (dBV), watts, etc. units Magnetomotive force converter Magnetic field strength converter Magnetic flux converter Magnetic induction converter Radiation. Ionizing Radiation Absorbed Dose Rate Converter Radioactivity. Radioactive Decay Radiation Converter. Exposure Dose Converter Radiation. Absorbed Dose Converter Decimal Prefix Converter Data Transfer Typography and Image Processing Unit Converter Timber Volume Unit Converter Calculating Molar Mass Periodic Table of Chemical Elements D. I. Mendeleev

1 lux [lx] = 1.46412884333821E-07 watts per sq. cm (at 555 nm) [W / cm² (555 nm)]

Initial value

Converted value

lux meter-candela centimeter-candela foot-candela phot nox candela-steradian per sq. meter lumens per sq. meter lumens per sq. centimeter lumens per sq. foot watt per sq. cm (at 555 nm)

Mass concentration in solution

More about illumination

General information

Illuminance is a luminous quantity that determines the amount of light that hits a given area of ​​the body's surface. It depends on the wavelength of light, since the human eye perceives the brightness of light waves of different lengths, that is, different colors, in different ways. Illuminance is calculated separately for different wavelengths, since people perceive light with a wavelength of 550 nanometers (green), and colors that are nearby in the spectrum (yellow and orange), as the brightest. Light generated by longer or shorter wavelengths (violet, blue, red) is perceived as darker. Illumination is often associated with the concept of brightness.

Illumination is inversely proportional to the area over which the light falls. That is, when illuminating the surface with the same lamp, the illumination of a larger area will be less than the illumination of a smaller area.

Difference between brightness and illumination

Brightness Illumination

In Russian, the word "brightness" has two meanings. Brightness can mean a physical quantity, that is, a characteristic of luminous bodies equal to the ratio of the intensity of light in a certain direction to the area of ​​the projection of the luminous surface onto a plane perpendicular to this direction. It can also define a more subjective concept of overall brightness, which depends on many factors, such as the characteristics of the eyes of the person who is looking at this light, or the amount of light in the environment. The less light around you, the brighter the light source appears. In order not to confuse these two concepts with illumination, it is worth remembering that:

brightness characterizes light, reflected from the surface of a luminous body or sent by this surface;

illumination characterizes falling light onto the illuminated surface.

In astronomy, brightness characterizes both the emitting (stars) and reflective (planets) ability of the surface of celestial bodies and is measured on the photometric scale of stellar brightness. Moreover, the brighter the star, the lower the value of its photometric brightness. The brightest stars have negative stellar brightness.

Units

Illumination is most often measured in SI units. suites... One lux equals one lumen per square meter. Those who prefer imperial units to metric units use to measure illumination foot candela... It is often used in photography and cinema, as well as in some other areas. The foot is used in the name because one foot-candela denotes the illumination of one candela of a surface of one square foot, which is measured at a distance of one foot (a little over 30 cm).

Photometer

A photometer is a device that measures illumination. Usually the light is sent to a photo detector, converted into an electrical signal and measured. Sometimes there are photometers that work on a different principle. Most photometers provide lux information, although other units are sometimes used. Photometers, called exposure meters, help photographers and operators determine shutter speed and aperture. In addition, photometers are used to determine safe illumination in the workplace, in crop production, in museums, and in many other industries where it is necessary to know and maintain a certain illumination.

Illumination and safety in the workplace

Working in a dark room can lead to visual impairment, depression, and other physiological and psychological problems. That is why many labor protection rules include requirements for minimum safe illumination of the workplace. Measurements are usually carried out with a photometer, which gives the final result depending on the area of ​​propagation of the light. This is necessary in order to provide sufficient illumination throughout the room.

Illumination in photo and video shooting

Most modern cameras have built-in exposure meters to simplify the work of the photographer or operator. A light meter is necessary so that the photographer or operator can determine how much light needs to be transmitted onto the film or photomatrix, depending on the illumination of the object being shot. Illumination in lux is converted by the exposure meter into possible combinations of shutter speed and aperture, which are then selected manually or automatically, depending on how the camera is configured. Usually the combinations suggested depend on the settings in the camera and what the photographer or cameraman wants to portray. In the studio and on set, an external or in-camera light meter is often used to determine if the light sources being used are providing sufficient lighting.

To obtain good photographs or video footage in low light conditions, there must be enough light on the film or sensor. This is not difficult to achieve with a camera - you just need to set the correct exposure. The situation with video cameras is more complicated. For high quality video, you usually need to install additional lighting, otherwise the video will be too dark or with a lot of digital noise. This is not always possible. Some camcorders are specially designed for shooting in low light conditions.

Cameras designed for shooting in low light conditions

There are two types of cameras for low-light photography, some with higher-end optics and others with more advanced electronics. The optics let more light into the lens, and the electronics are better at processing even the smallest light that enters the camera. It is usually with electronics that the problems and side effects described below are associated. High-aperture optics allow you to shoot video of higher quality, but its disadvantages are additional weight due to the large amount of glass and a significantly higher price.

In addition, the quality of shooting is influenced by the single-matrix or three-matrix photo matrix installed in video and still cameras. In a three-matrix matrix, all incoming light is divided by a prism into three colors - red, green and blue. Image quality in dark conditions is better in three-array cameras than in single-array cameras, since less light is scattered when passing through a prism than when it is processed by a filter in a single-array camera.

There are two main types of photo matrices - charge-coupled devices (CCDs) and made on the basis of CMOS technology (complementary metal oxide semiconductor). In the first, a sensor is usually installed, which receives light, and a processor that processes the image. In CMOS sensors, the sensor and processor are usually combined. In low light conditions, CCD cameras usually produce better image quality, and the advantage of CMOS sensors is that they are cheaper and consume less power.

The size of the image sensor also affects the image quality. If shooting takes place with a small amount of light, then the larger the matrix, the better the image quality, and the smaller the matrix, the more problems with the image - digital noise appears on it. Larger sensors are installed in more expensive cameras, and they require more powerful (and, as a result, heavier) optics. Cameras with such matrices allow you to shoot professional video. For example, recently a number of films have appeared completely shot on cameras such as the Canon 5D Mark II or Mark III, which have a matrix size of 24 x 36 mm.

Manufacturers usually indicate in what minimum conditions the camera can operate, for example, with an illumination of 2 lux or more. This information is not standardized, that is, the manufacturer decides for himself which video is considered to be of high quality. Sometimes two cameras with the same minimum illumination value will give different shooting quality. The EIA (Electronic Industries Association) in the United States has proposed a standardized system for determining the sensitivity of cameras, but so far it is used only by a few manufacturers and is not universally accepted. Therefore, often, in order to compare two cameras with the same light characteristics, you need to try them in action.

At the moment, any camera, even one designed for low light conditions, can produce a picture of poor quality, with high graininess and afterglow. To solve some of these problems, it is possible to take the following steps:

• Shoot on a tripod;
• Work in manual mode;
• Do not use variable focal length mode, but instead move the camera as close to the subject as possible;
• Do not use auto focus and auto ISO selection - higher ISO values ​​increase noise;
• Shoot with a shutter speed of 1/30;
• Use diffused light;
• If it is not possible to install additional lighting, then use all possible light around, such as street lamps and moonlight.

Despite the lack of standardization about the sensitivity of cameras to light, for night photography it is still better to choose a camera that says it works at 2 lux or lower. Also keep in mind that even though the camera is really good at shooting in dark conditions, its Lux sensitivity to illumination is the sensitivity to light directed at an object, but the camera actually receives light reflected from the object. When reflected, part of the light is scattered, and the further the camera is from the object, the less light enters the lens, which degrades the quality of shooting.

Exposition number

Exposition number(English Exposure Value, EV) - an integer characterizing possible combinations excerpts and diaphragms in a photo, film or video camera. All combinations of shutter speed and aperture, in which the same amount of light falls on the film or photosensitive matrix, have the same exposure number.

Several combinations of shutter speed and aperture in the camera at the same exposure number allow you to get approximately the same image density. However, the images will be different. This is due to the fact that at different aperture values, the depth of field will be different; at different shutter speeds, the image on the film or matrix will remain for different times, as a result of which it will be blurred to varying degrees or not at all. For example, combinations of f / 22 - 1/30 and f / 2.8 - 1/2000 are characterized by the same exposure number, but the first image will have a greater depth of field and may be blurry, and the second will have a shallow depth of field and, quite possibly will not be blurry at all.

Higher EV values ​​are used when the subject is better lit. For example, an exposure value (at ISO 100) EV100 = 13 can be used when shooting a landscape if the sky is cloudy, and EV100 = –4 is suitable for shooting a bright aurora.

A-priory,

EV = log 2 ( N 2 /t)

2 EV = N 2 /t, (1)

where
• N- f-number (for example: 2; 2.8; 4; 5.6, etc.)
• t- shutter speed in seconds (for example: 30, 4, 2, 1, 1/2, 1/4, 1/30, 1/100, etc.)

For example, for a combination of f / 2 and 1/30, the exposure value is

EV = log 2 (2 2 / (1/30)) = log 2 (2 2 × 30) = 6.9 ≈ 7.

This number can be used for night scenes and illuminated shop windows. A combination of f / 5.6 with a shutter speed of 1/250 gives an exposure value

EV = log 2 (5.6 2 / (1/250)) = log 2 (5.6 2 × 250) = log 2 (7840) = 12.93 ≈ 13,

which can be used to capture a landscape with a cloudy sky and no shadows.

It should be noted that the argument of the logarithmic function must be dimensionless. In determining the exposure value EV, the dimension of the denominator in formula (1) is ignored and only the numerical value of the shutter speed in seconds is used.

The relationship of the exposure number with the brightness and illumination of the subject

Determining the exposure by the brightness of the light reflected from the subject

When using exposure meters or lux meters that measure the light reflected from the subject, shutter speed and aperture are related to the brightness of the subject as follows:

N 2 /t = LS/K (2)

• N- f-number;
• t- exposure in seconds;
• L- average scene brightness in candelas per square meter (cd / m²);
• S- arithmetic value of photosensitivity (100, 200, 400, etc.);
• K- calibration factor of the exposure meter or lux meter for reflected light; Canon and Nikon use K = 12.5.

From equations (1) and (2) we obtain the exposure number

EV = log 2 ( LS/K)

2 EV = LS/K

At K= 12.5 and ISO 100, we have the following equation for brightness:

2 EV = 100 L/12.5 = 8L

L= 2 EV / 8 = 2 EV / 2 3 = 2 EV – 3.

Illumination and museum exhibits

The rate at which museum exhibits decay, fade and otherwise deteriorate depends on their illumination and on the strength of the light sources. Museum staff measure the illumination of exhibits to make sure that a safe amount of light is entering the exhibits, and also to provide enough light for visitors to get a good look at the exhibit. Illumination can be measured with a photometer, but in many cases it is not easy, since it must be as close to the exhibit as possible, and for this it is often necessary to remove the protective glass and turn off the alarm, as well as obtain permission for this. To facilitate the task, museum workers often use cameras as photometers. Of course, this is not a substitute for accurate measurements in a situation where a problem is found with the amount of light that enters the exhibit. But in order to check whether a more serious check with a photometer is needed, a camera is enough.

The exposure is determined by the camera based on the light readings, and knowing the exposure, you can find the light with a few simple calculations. In this case, museum staff use either a formula or a table with the conversion of exposure into light units. During calculations, do not forget that the camera absorbs part of the light, and take this into account in the final result.

Illumination in other areas of activity

Gardeners and plant breeders know that plants need light for photosynthesis, and they know how much light each plant needs. They measure light in greenhouses, orchards and vegetable gardens to make sure each plant is getting enough light. Some people use photometers for this.

Do you find it difficult to translate a unit of measurement from one language to another? Colleagues are ready to help you. Post a question to TCTerms and you will receive an answer within a few minutes.

Illumination is the most common photometric value, in everyday life it is defined in simple terms: light, dark, twilight, etc. The level of illumination has a significant impact on a person's well-being and ability to work, his ability to receive information from a variety of sources with the help of sight. To create comfortable conditions, it is necessary to measure the illumination and determine the optimal values.

Illumination concept

Determination of illumination is impossible without the use of other parameters of visible light - light units:

• Candela (cd). Luminous intensity refers to the basic units of the international SI system. The previously used name is a candle that served as a reference for measurements. Now one candela is the luminous efficiency of a monochrome emitter at a strictly defined frequency, with a given energy. In domestic use, one candela corresponds to the luminous intensity of one ordinary candle, 100 cd - an incandescent lamp with a power of 100 W;
• Luminous flux - lumen (lm), a derived unit of measurement. The definition is closely related to the intensity of light. 1 lumen is the luminous flux of the emitter with a force of one candela, distributed in one steradian (solid angle): 1 lm = 1 cd ∙ 1 sr. Typical values ​​for 100 W incandescent bulbs with a transparent bulb are 1300-1400 lumens.

Illumination depends on these characteristics of the light source and indicates the amount of luminous flux incident on a certain area, measured in lux (lx). Lux is taken as a unit of illumination - this is a luminous flux of one lumen, falling perpendicular to 1 m2 of the illuminated area and evenly distributed over it. It is also defined as the illumination of a sphere with a radius of 1 meter, located inside an emitter with a luminous intensity of 1 cd. It is directly proportional to the intensity of the source and inversely proportional to the square of the distance to it. The source is taken to be an isotropic (isotropic) point emitter that uniformly emits light in all directions.

The calculation of the specific value of candelas, lumens and lux is made according to the formulas:

E = F / S, where E - illumination, lux; S - area, m2.

E = I / R2, where R is the distance to the source.

From these ratios, it is clear how to convert suites to lumens, calculate the required flow at a certain illumination:

F = E × S, where F is the desired luminous flux in lumens, E is the known illumination, lux, S is the area, m2.

The value decreases if the light falls at an angle, then the result must be multiplied by the value of the cosine of the angle of incidence of the rays:

E = (F / S) × cos i;

E = (I / R2) × cos i.

In traditional English and American measurement systems, the concept of foot - candela is used. It is defined as the illumination at a distance of one foot produced by a source of one candela luminous intensity. More than one suite is approximately ten times, it is convenient to use online calculators for conversion.

Average values ​​for some common natural and artificial light sources:

• Sun, at mid-latitudes, noon - up to 400,000 lux;
• Cloudy weather - 3000 lux;
• Sunrise - 1000 lux;
• Full moon without clouds - up to 1 lux;
• Stadium under artificial lighting - up to 1300 lux.

The indicated values ​​are approximate and cannot be used for calculations - the difference in measurements can be very large.

Primary requirements

The illumination of any object on which the luminous flux falls does not depend in any way on its properties - they determine only the reflectivity of the surface, which is commonly called luminosity or brightness. Reflected light from the ceiling, mirrors and other structures is often used to enhance the efficiency of the main lighting, as most pendant lighting designs provide for the direction of a part of the light to the upper hemisphere.

• Living room - 200 lux;
• Bathroom, shower room - 80 lux;
• Cabinet - 300 lux;
• Utility rooms - 50 lux.

For production and service facilities, standardized values ​​have been established, specified in the SNiP rulebook.

Lighting is calculated using cumbersome formulas, which include many parameters: lux and lumens, area, various coefficients, how many lamps, etc. For simple applications, there are many calculators on the Internet that greatly facilitate calculations.

Measurement

Direct measurement of illumination is carried out with a special device - a luxmeter, which displays the result directly in lux. Works on the principle of the photoelectric effect inherent in some materials: a selenium element or semiconductors. In photography, exposure meters are used, which give the result in exposure numbers EV.

The light meter registers the luminous flux in a specific place, taking into account all types of lighting: artificial, natural, reflected.

Light source designations

The ability of a lighting product to create a certain level of illumination is indicated as the value of the luminous flux in lumens.

The parameter can be indicated as efficiency, in lumens per watt (lm / W), to decode it must be multiplied by power. For a 10 W and 150 lm / W lamp, the luminous flux will be 1500 lm.

In most cases, the packaging contains comparative characteristics with incandescent lamps, often overstated. To receive guaranteed result it is better to reduce the power of the traditional source by 15-20%.

The illumination of the workplace, recreation areas, as a rule, is selected individually, except for production or office. Therefore, the most correct way to select luminaires and their quantity is the user's practical experience and preferences.

Video

Characteristics of the main indicators as applied to lighting: suites, lumens, kelvin, watts. Read on!

Given the current economic situation in our country, now is the time to switch to LED lighting. Why? LED lamps consume much less electricity compared to other light sources, and in terms of their technical characteristics they significantly surpass, for example, the same incandescent lamps.

However, before you go to the LED equipment store, you need to know some of the characteristics of such devices, taking into account which you can choose exactly the lighting device whose characteristics will fully meet the operating conditions. In this article, we will talk about what watts, lumens, lux and kelvin mean on LED markings, and also talk about the advantages of LED devices over other light sources.

Watts, lux, lumens, kelvins, as the main characteristics of LEDs

When buying incandescent lamps, the consumer is guided by the number of watts indicated on the label, thereby determining how bright the product will shine. In LEDs, this figure has a completely different meaning.

The number of watts indicated by the manufacturer on the packaging does not characterize the brightness of the device, but the amount of electricity consumed per hour of operation. Naturally, you can draw a parallel between incandescent lamps and LEDs, focusing only on power. There are even special tables for this. So, for example, an LED device with a power of 8-12 watts will shine as brightly as an incandescent lamp with a characteristic of 60 watts. However, the basic unit that determines the brightness of LED lamps is lumens.

What are lumens in LED bulbs

By lumen is meant the amount of luminous flux that is emitted by a source of illumination with a force equal to one candela per angle of one steradian.

For example! An incandescent lamp with a power of 100 W is able to create a luminous flux equal to 1300 lumens, while a much lower power LED is able to produce a similar indicator.

However, in addition to lumens, LED equipment is also characterized by the amount of illumination, which is measured in lux.

What is Lux in Lighting

Lux is a unit of measure for illumination, which equals the illumination of a surface of one square meter with a luminous flux equal to one lumen. So, for example, if you project 100 lumens onto an area of ​​1 square meter, then the illumination index will be 100 lux. And if a similar luminous flux is directed over ten square meters, then the illumination will be only 10 lux.

Now, when you are asked: "suites and lumens, what is the difference?", You can show off your knowledge and give the interlocutor an exhaustive answer to his question.

What is Kelvin in lighting

As you've probably noticed, incandescent light has a warm yellowish tint, while LEDs have a wide color gamut. So, LED equipment is capable of displaying colors from violet to red (in the spectrum of white and yellow colors). However, the most common colors are bright white, soft or warm white. Why are we telling you this? The thing is that you can determine the color of light by marking the product. To do this, you need to look at such technical characteristics as color temperature, which is measured in Kelvin. The lower the number, the more yellow (warmer) the light will be emitted.

For example, a typical incandescent lamp has a color temperature that ranges between 2700 - 3500 Kelvin. Thus, if you are looking to purchase an LED lighting fixture that has the same color as an incandescent lamp, choose an LED fixture with a similar color temperature.

Various types of industrial lamps, their advantages and disadvantages

Below is given comparison table various types of industrial lamps.

Based on this table, we can conclude that LED lamps are superior to other types of lighting elements in almost all respects. As for the price, this factor can hardly be called a significant drawback. In addition, with the question of choosing and installing LED equipment, for example, it will pay for itself in a relatively short time.

Consult about technical characteristics and LED industrial lighting, as well as choose from the product you need, you can on our website. Also, our specialists will carry out the current lighting at your facility and offer a suitable system for modernization.

More details

29 Mar

Kiev authorities will allocate 700 million to replace street lighting

More details

Export stories: how Ukraine "brings light" to Europe

More details

Modernization of the electric lighting system at DTEK Dobropolskaya CEP

More details

What is heat sink in LED lamp?

More details

How much electricity can be saved per year using LED lighting?

More details

20 Sep

Energy efficient lighting as a competitive advantage

More details

Features of the operation of LED lighting

More details

Lighting automation

More details

Return on investment in lighting upgrades

In Soviet times, when choosing a light bulb, consumers were guided by the number of watts in it. The more there are, the brighter it shone this device... However, today (when many new varieties of lamps have appeared on store shelves) more and more often one has to deal with such a concept as "lumen". What is it, how is it different from a watt and what unit is called a lumen per watt? Let's find the answers to these questions.

What is "lumen"

In the middle of the twentieth century. to avoid confusion in units of measurement between different countries, the universal SI system was introduced. It is thanks to her that we have watts, amperes, meters, kilograms, etc.

According to her, (visible electromagnetic radiation) is In fact, these units measure the amount of light emanating from its source.

Also, when asked what “lumen” is, one can answer that this is the name of a famous Russian rock group from Ufa. Having started its activity in 1998, it has continued to be loved by many listeners for almost twenty years. Russian Federation and beyond.

Origin of the word

Having learned what a lumen is, it is worth clarifying where this word came from in the Russian language.

Like most names for units of measurement in the SI system, the term in question is Latinism. It is derived from the word "light" (lūmen).

At the same time, some linguists argue that the noun could be formed from the Proto-Indo-European word leuk (white) or from lucmen (the meaning has not been established exactly).

What is the difference between lumen and luxury

Considering the meaning of the word "lumen", it is worth mentioning such a close concept as "luxury".

Both of these terms refer to light energy units, however, lumen is all the light emitted by the source, and lux is the amount that reached the illuminated surface, and was not stopped by some kind of obstacle with the formation of shadows.

The interdependence of these units can be reflected with the following formula: 1 lux = 1 lumen / 1 square meter.

For example, if a lamp illuminating an area of ​​1 m 2 emits 50 lumens, then the illumination of this place equal to 50 lux (50lm / 1m 2 = 50 lux).

However, if the same lamp with the same amount of light is used for a room of 10 m 2, then the illumination in it will be less than in the previous case. Only 5 suites (50lm / 10m 2 = 5 lux).

In addition, such calculations did not take into account the presence of various obstacles that prevent the light rays from reaching the surface, which significantly reduces the illumination level.

In connection with this situation, in any country in the world, there are lighting standards for various buildings. If it is lower than them, the person's vision receives less light and deteriorates. For this reason, when planning to make repairs or rearrangements in your home, it is always important to take this nuance into account.

There are also a number of design programs in which such calculations are made automatically.

Lumen and watt

Having learned the difference and the meaning of lumen and lux, it is worth paying attention to one more unit of the SI system - watt.

Due to the fact that they are used for light bulbs, some believe that these units can be freely correlated with each other. However, this is not quite true.

The fact is that in watts the power of the energy that a light bulb consumes is measured, and in lumens - the amount of light that it emits.

At the time of the existence of only incandescent lamps, it was easier to calculate the amount of light from such a device. Since a 100 W bulb gave out about 1600 lumens of light. While a similar device in 60 W - 800 lumens. It turned out that the more energy consumed, the better the lighting.

But today it’s not like that. In recent decades, several new types of fluorescent light sources have been invented, etc.). Their advantage is economy. That is, they shine brighter with less energy used.

In this regard, if it is necessary to draw up the ratio between watts and lumens, you need to take into account the type of lamp and look for its luminosity in special tables.

It is worth noting that an ordinary person sometimes does not want to rebuild and understand all these subtleties. Therefore, most domestic producers new type of bulbs on the labels indicate not only the number of lumens, but how much less watts a given device consumes (compared to an incandescent lamp). For example: a 12 watt lamp gives out light as 75 watt.

Unit of measurement "lumen per watt": its value and scope

For example, a classic 40 W incandescent lamp has a luminous efficacy of 10.4 lm / W. At the same time, for an induction lamp with the same power, this figure is much higher - 90 lm / W.

For this reason, when choosing a lighting device for your home, you should not be too lazy, but find out the level of its light output. As a rule, such data is on the labels.