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Illuminator calculation

 Luminaire parameters

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Illuminator calculation

 Luminaire parameters

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Illuminator calculation

 Luminaire parameters

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Luminaire parameters are located on the Luminaire panel, on the right half of the Illuminator calculation box.

 

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To allow for lamp aging, supply voltage deviation, as well as luminaire dirt depreciation in operation it is necessary to set Maintenance factor of illuminators on the 3D modeling tab of the Options box according to CIE 97.

 

In case of modeling infra-red illuminator, see IR illuminators.

 

Lamp quantity

Efficiency factor

Light flux emitted by Illuminator (lm)

 

Omnidirectional light source

Light intensity (cd)

 

Projector

Angle of radiation (deg.)

Concentration

Axial light intensity (cd)

 

Illumination at distance

Distance (m. or ft.)

Illumination (lux)

 


Lamp quantity

 

Number of lamps in the Luminaire.

 

Lamp parameters are set on the Lamp panel.

 

Efficiency factor

 

Efficiency of the luminaire.

 

A part of the luminous flux emitted by lamps is consumed inside the luminaire or is emitted outside the angle of radiation.

 

Efficiency factor of the luminaire is a ratio of the light flux emitted within the limits of radiation angle to the total light flux of all lamps.

 

Typical values of efficiency factor for new luminaires:

 

For luminaires with angle of radiation of more than 100 degrees - 0.6-0.9;
For luminaires with angle of radiation of 50-100 degrees - 0.5;
For luminaires with angle of radiation of 20-50 degrees - 0.4;
For luminaires with smaller angle of radiation, the efficiency factor can reach up to 0.2.

 

For IR illuminators the recommended efficiency factor is 0.3-0.5.

 

In IR illuminators a part of consumed power is lost in internal circuits and filter.

 

In operation the luminaire efficiency factor is reduced depending on environment contamination.

 

It is possible to allow for environment contamination through the maintenance factor of illuminators.

 

The efficiency factor is sometimes given in the luminaire specification, but the light intensity curves with the lamp with full light flux of 1000 lumen are given more often. In this case, it is necessary to select efficiency factor in this box to obtain light intensity value, recalculated according to light flux of the lamp in the luminaire.

 

For example: The total light flux of all lamps is F=3000 lumen. In this case an axial light intensity value obtained from the light intensity curves (with the lamp of 1000 lumen) has to be multiplied by 3.

 

Light flux emitted by Illuminator (lm)

 

The light flux of the illuminator within the limits of angle of radiation. The light flux of the illuminator equals to the total light flux of all lamps, multiplied by efficiency factor of the luminaire.

 

Omnidirectional light source

 

The illuminator emits light in all directions with equal light intensity.

For example, a lamp without reflector.

 

An omnidirectional illuminator has one parameter - light intensity (candela).

 

Light intensity (cd)

 

Light intensity of the omnidirectional illuminator, equal in every direction. It is the most important parameter of the illuminator.

 

Projector

 

An illuminator with limited angle of radiation. The majority of real luminaires have limited angle of radiation.

 

Angle of radiation (deg.)

 

The full angle of radiation at the top of the light cone. The light flux of the illuminator is emitted within the limits of this angle.

The angle of radiation influences illumination area and light intensity of the illuminator. Having identical lamps, the luminaire with a smaller angle of radiation will have higher light intensity and, therefore, produces higher illumination.

 

Concentration

 

The ratio of light intensity on the borders of the radiation cone to light intensity on the axis of the radiation cone.

Real luminaires have irregular light distribution within the limits of the radiation cone. As a rule, light intensity is maximal in the center of the cone.

 

In luminaire specification the light intensity curves with the lamp with full light flux of 1000 lumen are given. During construction or editing of the illuminator in the Graphics window, the light intensity curves of the luminaire model are displayed.

By moving grips in the Graphics window (Ctrl is pressed) or by changing concentration it is possible to reach closer light intensity distribution. High precision is not required; a rough correspondence of the light intensity curves is enough. The axial light intensity should be selected more precisely.

 

When changing concentration, the full light flux of the illuminator is not changed. If light intensity increases on the radiation axis, it weakens on the borders of the radiation cone and vice versa.

 

Using one illuminator model in VideoCAD it is possible to model only a point light source with round symmetrical light intensity distribution. Luminaires with non-round symmetrical light intensity distribution can be modeled by one illuminator only roughly. For accurate modeling several illuminators should be used.  Recount their light fluxes, reaching the light intensity value similar to light intensity value of the real luminaire.

 

Axial light intensity (cd)

 

Light intensity on axis of radiation.

It is the most important parameter of the luminaire. All the previous parameters are used for estimation of the light intensity.

 

If there are the light intensity curves with the lamp with full light flux of 1000 lumen in the luminaire specification, light intensity should be recalculated in proportion to the total light flux of the real lamps in the luminaire.

 

For example: the total light flux of lamps is 3000 lumen. In this case the axial light intensity value obtained from light intensity curve (with lamp of 1000 lumen) has to be multiplied by 3.

 

Then by selecting the efficiency factor, it is necessary to reach an equal value of the axial light intensity.

 

If there are no light intensity curves in the specification, but there is an axial light intensity value, it is necessary to select an efficiency factor value for obtaining the equal axial light intensity.

 

If in the specification there are no such parameters, or the specification is absent, only estimation is possible. Specify  0.5 as the efficiency factor value and concentration =0.5. In practice, the estimation is usually enough.

 

Illumination at distance

 

On the panel you can calculate illumination produced by the illuminator on the specified distance. For projector illumination is calculated on axis of radiation.

 

Values on this panel are given only for information and do not influence parameters of the illuminator model.

 

Illumination is calculated on the plane perpendicular to axis of radiation.

 

By means of luxmeter you can verify illumination value on the specified distance from the real luminaire and by selecting parameters reach complete identity of the model and the real luminaire.

 

Distance (m. or ft.)

 

Distance from the luminaire on which illumination is calculated. The distance is measured in meters or foots depending on measuring formats in the project.

 

Illumination (lux)

 

The calculated illumination. As in CCTV the sensitivity of cameras is measured only in lux, illumination is displayed in luxes irrespective of the measuring format in the project.

 

1 foot-candela equals 10.76 lux.

 

 

See also: Illuminator calculation, Lamp parameters, IR illuminators, Illuminator, Current construction parameter panel>Illuminator, 3D Video>Image parameters panel>Scene.

External link: "The principles of CCTV design in VideoCAD. Part 4. Illumination and camera sensitivity in CCTV"(*.pdf) .