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 using vision. To create comfortable conditions, it is necessary to measure the illumination and determine the optimal values.

Illumination concept

Determining illumination is impossible without using other parameters of visible light - light units:

• Candela (cd). Luminous intensity is one of the basic units of the international SI system. The previously used name was a candle, which served as a standard 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 corresponds to a 100 W incandescent lamp;
• 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 an emitter with an intensity of one candela, distributed over one steradian (solid angle): 1 lm = 1 cd ∙ 1 sr. The typical value for 100 W incandescent lamps with a transparent bulb is 1300-1400 lm.

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). A lux is taken as a unit of illumination - this is a luminous flux of one lumen falling perpendicularly onto 1 m2 of 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 by 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 a point emitter uniformly emitting light in all directions.

The specific values ​​of candelas, lumens and lux are calculated using 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 lux to lumens, calculate the required flux 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 cosine value of the angle of incidence of the rays:

E = (F / S) × cos i;

E = (I / R2) × cos i.

In the traditional English and American measurement system, the concept of foot-candela is used. Defined as the illuminance at a distance of one foot produced by a source of luminous intensity of one candela. More than one lux is approximately ten times; for conversion it is convenient to use online calculators.

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

• Sun, in mid-latitudes, noon - up to 400,000 lux;
• Cloudy weather – 3000 lux;
• Sunrise – 1000 lux;
• Full moon without clouds – up to 1 lux;
• Stadium with 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 light flux falls does not depend in any way on its properties - they determine only the reflective ability of the surface, which is usually called luminosity or brightness. Reflected light from the ceiling, mirrors and other structures is often used to enhance the effectiveness of the main lighting, so most designs of pendant lamps provide for the direction of part of the light into the upper hemisphere.

• Living room – 200 lux;
• Bathroom, shower – 80 lux;
• Office – 300 lux;
• Utility rooms – 50 lux.

For production and service facilities, standardized values ​​are established, specified in the SNiP set of rules.

Lighting calculations are made 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 the calculations.

Measurement

Direct measurement of illumination is carried out by a special device - a lux meter, which displays the result directly in lux. It works on the principle of photoelectric effect, characteristic of some materials: selenium element or semiconductors. In photography, exposure meters are used that give results in EV exposure numbers.

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

Symbols on light sources

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

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

In most cases, the packaging shows comparative characteristics with incandescent lamps, which are often inflated. To obtain a guaranteed result, it is better to reduce the power of the traditional source by 15-20%.

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

Video

You will learn about this by reading the article below.

Lumen (lm, lm) is a unit of measurement of luminous flux in the SI system.

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 equal to 4 lumens.

A typical 100 W incandescent lamp produces a luminous flux of approximately 1300 lm. A 26 W compact fluorescent fluorescent lamp produces a luminous flux of approximately 1600 lm.

Lumen - The total luminous flux from a source. However, this measurement usually does not take into account the focusing efficiency of the reflector or lens and is therefore not a direct parameter for assessing the brightness or useful performance of a flashlight beam. A wide beam of light can have the same lumens as a narrowly focused beam. Lumens cannot be used to determine the intensity of a beam because the lumen rating includes all scattered, wasted light.

Lux (symbol: lux, lx) is a unit of measurement of illumination in the SI system.

Lux is equal to the illumination of a surface with an area of ​​1 m² when the luminous flux of radiation incident on it is equal to 1 lumen.

100 lumens were collected and projected onto a 1-meter square area.

The illumination of the area will be 100 lux.

The same 100 lumens aimed at 10 square meters will give an illumination of 10 lux.

Candela (symbol: cd, cd) - one of the seven basic units of measurement of the SI system, is equal to the intensity of light emitted in a given direction by a source of monochromatic radiation with a frequency of 540·1012 hertz, the energy intensity of which in this direction is (1/683) W/ Wed

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 greater energy intensity is required to achieve the same luminous intensity.

Previously, candela was defined as the intensity of light emitted by a black body perpendicular to a surface with an area of ​​1/60 cm? at the melting point of platinum (2042.5 K). In the modern definition, the coefficient of 1/683 is chosen so that the new definition matches the old one.

The intensity of light emitted by a candle is approximately equal to one candela (Latin candela - candle), so this unit of measurement was previously called a “candle”, now this name is outdated and is not used.

Warning on line 35

Warning: preg_replace(): Unknown modifier "2" in /var/www/u0413025/data/www/site/wp-content/plugins/realbigForWP/textEditing.php on line 35

Lumen is a unit of measurement for the brightness of radiation. It is a light quantity in the international system of units. Lumen characterizes the amount of light emitted by a source. It is a more accurate value than power, since light sources with the same power, but different efficiency and spectral characteristics, emit a different flux of light.

What is a lumen?

There are several units for measuring illumination. The main values ​​are lux and lumen. Their difference is that lux shows the illumination of a unit surface area, and lumen is a unit of measurement of the entire radiation flux of a light source. Thus, the higher the lux value, the brighter the surface is illuminated, and the higher the lumen, the brighter the lamp itself. This difference helps to evaluate the effectiveness of lighting devices of various designs.

It is necessary to consider what lumens are in LED lamps. This will help to understand the fact that such light sources are characterized by directional radiation. Incandescent and fluorescent lamps emit light in all directions. To obtain the same surface illumination, LED elements of lower brightness are required, since the radiation is concentrated in one direction.

Incandescent and economical lamps produce non-directional radiation, which requires the use of reflectors (reflectors) that redirect the flow of light in the required direction. When using LED devices, there is no need for reflectors.

Parameters that determine the luminous flux indicator and its calculation

Lighting parameters are affected not only by the brightness level of lighting sources. Should be taken into account:

1. The wavelength of the emitted light. Lighting with a color temperature of 4200 K, which corresponds to natural white color, is better perceived by vision than something closer to the red or blue part of the spectrum.
2. Direction of light propagation. Narrowly focused lighting fixtures allow you to concentrate the light emission in the right place without installing brighter lamps.

Luminous flux in lumens is rarely indicated by manufacturers, since most buyers are guided by the power of the lamps and their color temperature.

How many lumens in 1 W LED light bulb

Manufacturers of lighting equipment do not always include a complete list of characteristics on product packaging. This could be for several reasons:

• the habit of buyers to evaluate the brightness of light bulbs by power consumption;
• Unscrupulous manufacturers do not bother to take the necessary measurements.

The problem is that the level of radiation from LEDs and structures made on their basis is unequal:

• part of the flow is delayed by a protective flask;
• There are several LEDs in an LED lamp;
• part of the power is dissipated on the LED driver;
• Brightness depends on the amount of current flowing through the LED.

An accurate determination is only possible with the help of measuring instruments (lux meters), but for some types of LEDs it will be possible to provide approximate data:

• LEDs in a frosted bulb – 80-90 Lm/W;
• LEDs in a transparent bulb – 100-110 Lm/W;
• single LEDs – up to 150 Lm/W;
• experimental models - 220 Lm/W.

The listed data can be used to determine the current consumption when using LED devices for which the brightness value is determined. If an LED spotlight with transparent protective glass is installed and its brightness parameter is stated as 3000 lumens, then the power consumption will be 30 W. Knowing the power and supply voltage, it is easy to determine the current consumption.

Converting lumens to watts

To compare the efficiency of light sources of various types and designs, it is convenient to have in front of you a table that contains data on the power of lighting devices with the same brightness values.

Residential lighting standards

The illumination of rooms for different purposes is not the same and can vary by an order of magnitude. The number of lumens per square meter by type of residential premises is as follows:

• office, library, workshop – 300;
• children's room – 200;
• kitchen, bedroom – 150;
• bathhouse, sauna, swimming pool – 100;
• wardrobe, corridor – 75;
• hall, corridor, bathroom, toilet – 50;
• staircase, basement, attic – 20.

Calculation of illumination for premises

To determine the illumination of a room, you need to know the following parameters:

1. E – standard value of illumination (how many lumens are needed per 1 square meter).
2. S – area of ​​the room.
3. k – height coefficient:
   • k = 1 with a ceiling height of 2.5 – 2.7m;
   • k = 1.2 with a ceiling height of 2.7 – 3.0 m;
   • k = 1.5 with a ceiling height of 3.0 – 3.5 m;
   • k = 2 with a ceiling height of 3.5 – 4.5 m;

The formula for calculation is simple:

Knowing the illumination, you can select the required luminous flux and power of lighting lamps, taking into account their differences in production technologies and operating principles. One should take into account the peculiarities of human vision, for whom light sources with a bluish tint (from a color temperature of 4700K and above) seem less bright.

Comparative characteristics of an incandescent lamp and an LED lamp

Above was a table that compared the power of different types of devices for the same brightness value. The table shows how many lumens are in an incandescent lamp, in fluorescent and LED lamps.

The efficiency of devices varies by more than an order of magnitude. It is immediately clear that the comparison is in favor of modern light sources. And this doesn’t even take into account the long durability of LED lighting sources. According to some manufacturers, the lifespan of LED elements can be tens of thousands of hours. The energy savings over the service life pay for the high cost of LED light sources many times over.

100 W incandescent lamps are the most suitable for lighting domestic premises. Unsatisfactory efficiency and low service life have led to the fact that light sources with incandescent filament are being replaced by more modern, efficient and durable devices. A 12 W LED lamp produces the same brightness as lumens in a 100 Watt incandescent lamp.

Often, lighting in a house or apartment is determined by a minimum of parameters. This is the lighting design and placement. And even knowing about illumination standards, many simply do not take them into account. This is certainly not a critical error. But if you select lighting according to the rules and standards of illumination, correctly calculate how much light is needed for a certain room in an apartment, you can achieve a stable psycho-emotional and physical state for a person.

How many lumens are needed for 1m2

An integral part of a comfortable stay at home or at work is lighting. Few people know that the right light helps relieve psychological stress or, on the contrary, concentrate on work. But before moving on to calculations, it is necessary to understand the measurement values. Lumen (Lm) is a unit of measurement of luminous flux, Lux (Lx) - the illumination of a surface is measured in lux. 1 lux is equal to 1 lumen per square meter.

Calculation (measurement) of lighting intensity is carried out using a simple formula (AxBxC) in which:

• A – required illumination according to SNiP standards;
• B – room area (sq. m);
• C – Height coefficient.

The height coefficient is a correction value and is calculated depending on the height of the ceiling. 2.5 and 2.7 – the coefficient is equal to one; if 2.7 and 3 meters - 1.2; ceilings with a height of 3 and 3.5 meters - 1.5; from 3.5 to 4.5 meters – coefficient is 2.

Table of illumination standards according to SNiP in lux (Lx):

We make a calculation. Suppose you need to find out the required amount of light for a children's room, the area of ​​which is 15 square meters, with a ceiling height of 2.7 m. For accuracy, we use a calculator. We multiply the amount of illumination by square meters and by the height coefficient - 200 x 15 x 1 = 3000. Accordingly, the luminous flux should be 3000 lumens (Lm).

Divide rooms of irregular shape into shapes (for example, a square and a triangle), and perform the calculation separately for each.

You can measure the level of illumination at home with a lux meter.

Living space lighting

Lighting in the house is as important as the interior. First of all, they divide the entire space into areas that differ not only in size, but also in functionality.

Namely:

1. Hallway– its location implies a lack of natural lighting, so artificial lighting is created in the hallway. For this purpose, directional lighting devices with wide dispersion angles are used.
2. Living room (hall)- a room with many functions. Therefore, maximum functionality is achieved with lighting, combining general with spot lighting.
3. Kitchen- an area that has separate work areas, in which spot lighting is added to the general one.
4. Bedroom– intended directly for rest and sleep. For bedrooms, soft and warm tones of artificial light are selected. Also, it makes sense for them to adjust the lighting intensity.
5. Bathroom– as in previous cases, local lighting is added to the main one.

When choosing a lighting fixture for a bathroom, you need to make sure that this sample has a high degree of protection (IP) from humidity.

Proper lighting in the apartment will help not only emphasize or highlight a certain area, but also erase visual boundaries.

LED lamps for residential premises

Some time ago, LED lighting was considered unacceptable for the home. The main factors were the high price, as well as the brightness and color of the lighting.

But today, such lighting is becoming relatively inexpensive. And the choice in power, design, range and size is simply huge. The only limitation can be your imagination, where and how to use LED lamps. Also, such lamps have a number of advantages.

Advantages:

• Low energy consumption (allows long-term use to quickly recoup the cost of the lamp);
• Durability (if you choose a quality product, the service life is many times longer than that of conventional incandescent, fluorescent and halogen lamps);
• Does not heat up during operation (which increases the possibilities of placement in accordance with the design).

And these are not all indicators. The optimal lighting option can be selected based on spectrum and brightness (all values ​​are indicated on the product packaging). For your home, choose lamps that provide warm light.

When choosing LED lamps, pay attention to the manufacturer. The more famous the brand, the better the product.

An important factor is environmental friendliness. LED lamps do not emit UV radiation, and they do not create fluctuations in light output.

If you decide to make good lighting in your home, then it is better to choose LED lamps.

Illumination standards for office premises: required value

It is not so common to find offices in which special attention was paid to lighting. Usually these are luminous squares with luminescent flickering, built into the ceiling. But light affects both the psychological and emotional state of a person. With proper lighting, you can achieve high employee productivity throughout the day.

The level of illumination in the office is determined by two standards:

• Russian – illumination level (required scale), recommended within 300 – 400 lux (Lx);
• International standard (European standards) – 500 lux (Lx).

Lighting is divided into both general (direct and reflected), light from light sources is scattered throughout the entire office area, and local (lighting directly at the workplaces themselves), illumination is carried out by various lighting devices for local lighting (table lamps and lamps).

The placement of lighting fixtures parallel to the windows is the most correct; this ensures that the light from the lamps matches the light from the windows.

An individual approach to each workplace in the office is also important, this is due to the difference in lighting needs for each employee. This is influenced by factors such as vision and age.

Children's playground lighting: standards

Modern playgrounds, of course, differ from sports ones, but in terms of their functionality they can be equated to each other. In addition to the usual slides, swings and carousels, many sports equipment are added for the physical development of children. Therefore, competent and effective lighting for children's playgrounds is simply necessary.

With such characteristics, there are important parameters to consider for children's playgrounds.

List of parameters:

• Ensuring comfort and safety;
• Injury prevention;
• Possibility to be on site in the evening (especially in winter).

The lighting standard for children's playgrounds according to the Russian standard is 10 lux. But as sites are improved, the required (normal) level of illumination should be 70 - 100 lux.

The level of color rendering is of great importance when lighting children's playgrounds. For easy identification of small and moving objects.

In accordance with the size, the optimal ratio of height and location of lighting fixtures is selected for various playgrounds. These include cantilever (up to 10 meters high) and local (up to 4 meters high). The power of a separate street lighting device is calculated according to SNiP standards.

If the site is not sufficiently illuminated, the lighting must be improved by adding lighting fixtures.

It is worth taking into account the aesthetic component by choosing lamps that highlight the exterior of the site.

How many watts are needed to light a room: converting lumens to watts

The questions - how to determine what kind of lighting should be in a separate room or one room, how to convert lux into watts, how to select and calculate the required number of lamps - have fairly simple answers.

Let's do the calculation using an example. We need to illuminate a hall of 20 m2 with a chandelier with five incandescent light bulbs. What power in watts should I choose for lamps?

To calculate you will need:

• Illumination level;
• Area in square meters.

We multiply the illumination rate by square meters. 150 x 20 = 3000. The total luminous flux should be 3000 Lumens. This means that for normal lighting you will need 5 lamps of 60 watts each. If we convert to European standards, we get 4000 lumens.

Due to outdated standards, multiply the illumination rate by 1.5 times.

Do not forget, unlike incandescent lamps, there are several other types of artificial lighting sources that are more reliable and economical.

What are lighting standards (video)

The right light is needed not only at home or in the office. It is necessary for a comfortable stay in a hotel, walking along the street, its use in kindergartens and shopping malls is important. The only difference is purpose and functionality. Based on the tests conducted, psychologists have proven that with well-designed lighting, not only the psycho-emotional, but also the general condition of a person improves.

Length and distance converter Mass converter Converter of volume measures of bulk products and food products Area converter Converter of volume and units of measurement in culinary recipes Temperature converter Converter of pressure, mechanical stress, Young's modulus Converter of energy and work Converter of power Converter of force Converter of time Linear speed converter Flat angle Converter thermal efficiency and fuel efficiency Converter of numbers in various number systems Converter of units of measurement of quantity of information Currency rates Women's clothing and shoe sizes Men's clothing and shoe sizes Angular velocity and rotational speed 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 converter (by mass) Energy density and specific heat of combustion converter (by volume) Temperature difference converter Coefficient of thermal expansion converter Thermal resistance converter Thermal conductivity converter Specific heat capacity converter Energy exposure and thermal radiation power converter Heat flux density converter Heat transfer coefficient converter Volume flow rate converter Mass flow rate converter Molar flow rate converter Mass flow density converter Molar concentration converter Mass concentration in solution converter Dynamic (absolute) viscosity converter 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 Illuminance Converter Computer Graphics Resolution Converter Frequency and Wavelength Converter Diopter Power and Focal Length Diopter Power and Lens Magnification (×) Electric charge converter Linear charge density converter Surface charge density converter Volume charge density converter Electric current converter Linear current density converter Surface current density converter Electric field strength converter Electrostatic potential and voltage converter Electrical resistance converter Electrical resistivity converter Electrical conductivity converter Electrical conductivity converter Electric capacitance Inductance converter American wire gauge converter Levels in dBm (dBm or dBm), 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 converter Radiation. Exposure dose converter Radiation. Absorbed dose converter Decimal prefix converter Data transfer Typography and image processing unit converter Timber volume unit converter Calculation of molar mass D. I. Mendeleev’s periodic table of chemical elements

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

Initial value

Converted value

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

Specific fuel consumption

More about illumination

General information

Illuminance is a luminous quantity that determines the amount of light falling on a certain surface area of ​​the body. It depends on the wavelength of light, since the human eye perceives the brightness of light waves of different lengths, that is, different colors, differently. 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 produced 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 on which the light falls. That is, when illuminating a 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 illuminance

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 ​​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 eyes of the person looking at the light or the amount of light in the environment. The less light there is, 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 reflecting (planets) ability of the surface of celestial bodies and is measured on the photometric scale of stellar brightnesses. Moreover, the brighter the star, the lower the value of its photometric brightness. The brightest stars have a negative stellar brightness value.

Units

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

Photometer

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

Lighting and safety in the workplace

Working in a dark room threatens vision impairment, depression and other physiological and psychological problems. That is why many labor safety regulations include requirements for minimum safe illumination of the workplace. Measurements are usually carried out with a photometer, which produces the final result depending on the area of ​​light propagation. This is necessary in order to ensure sufficient illumination throughout the room.

Lighting in photography and video shooting

Most modern cameras have built-in exposure meters, making the work of the photographer or operator easier. An exposure meter is necessary so that the photographer or operator can determine how much light needs to be let into the film or photo matrix, depending on the illumination of the subject being photographed. 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. Typically, the combinations offered depend on the settings in the camera, as well as what the photographer or cinematographer wants to depict. Studios and film sets often use an external or in-camera light meter to determine whether the light sources being used provide sufficient illumination.

To take good photographs or video in poor lighting conditions, sufficient light must reach the film or sensor. This is not difficult to achieve with a camera - you just need to set the correct exposure. With video cameras the situation is more complicated. To shoot 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 specifically designed for shooting in low light conditions.

Cameras designed for shooting in low light conditions

There are two types of low-light cameras: some use higher-end optics, and others use more advanced electronics. The optics let more light into the lens, and the electronics better handle even the little light that gets into the camera. It is usually the electronics that cause the problems and side effects described below. High-aperture optics allow you to shoot higher-quality video, 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 affected by the single-matrix or three-matrix photomatrix installed in video and photo cameras. In a three-matrix array, all incoming light is divided into three colors by a prism - 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 the prism than when it is processed by the filter in a single-array camera.

There are two main types of photomatrices - charge-coupled device (CCD) and those based on CMOS (complementary metal oxide semiconductor) technology. The first usually contains a sensor that 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 generally produce better images, while CMOS cameras have the advantage of being cheaper and consuming less power.

The size of the photo matrix also affects 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. Large matrices 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 that were shot entirely 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 the minimum conditions in which the camera can operate, for example, with illumination of 2 lux or more. This information is not standardized, that is, the manufacturer decides for himself which video is considered high-quality. Sometimes two cameras with the same minimum illumination level produce different shooting quality. The Electronic Industries Association (EIA) in the United States has proposed a standardized system for determining the light sensitivity of cameras, but so far it is used only by some manufacturers and is not universally accepted. Therefore, in order to compare two cameras with the same light characteristics, you often need to try them in action.

At the moment, any camera, even one designed for low-light conditions, can produce low-quality images with high grain and afterglow. To solve some of these problems, you can take the following steps:

• Shoot on a tripod;
• Work in manual mode;
• Do not use zoom mode, but instead move the camera as close to the subject as possible;
• Do not use automatic focusing and automatic ISO selection - with a higher ISO value, noise increases;
• Shoot at 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.

Although there is no standardization about how cameras are sensitive to light, for night photography it is still best to choose a camera that says it operates at 2 lux or lower. Another thing to remember is that even if a camera is really good at shooting in dark conditions, its light sensitivity, listed in lux, is sensitivity to light directed at the subject, but the camera is actually receiving light reflected from the subject. When reflected, part of the light is scattered, and the further the camera is from the object, the less light enters the lens, which deteriorates the quality of shooting.

Exposure number

Exposure number(eng. Exposure Value, EV) - an integer characterizing possible combinations excerpts And aperture in a photo, film or video camera. All combinations of shutter speed and aperture that expose the same amount of light to the film or sensor have the same exposure number.

Several combinations of shutter speed and aperture in the camera at the same exposure number allow you to obtain an image of approximately the same density. However, the images will be different. This is due to the fact that at different aperture values, the depth of the imaged space will be different; at different shutter speeds, the image will remain on the film or matrix for different times, as a result of which it will be blurred to varying degrees or not blurred at all. For example, the combinations f/22 - 1/30 and f/2.8 - 1/2000 are characterized by the same exposure number, but the first image will have a large 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) of EV100 = 13 can be used when shooting landscapes if the sky is cloudy, and EV100 = –4 is suitable for shooting bright aurora.

A-priory,

EV = log 2 ( N 2 /t)

2 EV = N 2 /t, (1)

Where
• N- aperture 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 number

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

This number can be used to shoot night scenes and illuminated storefronts. Combining f/5.6 with a shutter speed of 1/250 gives the exposure number

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 shoot 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 number 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 between the exposure number and the brightness and illumination of the subject

Determining exposure by the brightness of light reflected from the subject

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

N 2 /t = L.S./K (2)

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

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

EV = log 2 ( L.S./K)

2 EV = L.S./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 .

Lighting and museum exhibits

The rate at which museum exhibits deteriorate, fade, and otherwise deteriorate depends on their illumination and the strength of the light sources. Museum staff measure the illumination of exhibits to ensure that a safe amount of light is reaching the exhibits, but also to ensure that there is enough light for visitors to see the exhibit well. Illumination can be measured with a photometer, but in many cases this is not easy as it needs to be as close to the exhibit as possible, and this often requires removing the protective glass and turning off the alarm, as well as obtaining permission to do so. To make things easier, 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 falls on the exhibit. But in order to check whether a more serious check with a photometer is needed, a camera is quite enough.

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

Lighting in other areas of activity

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

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