Lighting Calculator

Calculator

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(Consumption Watt - Lumens/Watt)

Luminous Flux (Lumens) Candelas (cd)

Illuminance (Lux) footcandles (fc)

LED Beam Angle

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Distance from Surface to Light (m)

m (ft)

Beam Width

m (ft)

Beam angle
Beam angle of a light indicates the spread of light from the light source.

The beam range is usually between 15° to 120°. A narrow beam is between 15° to 45° and a wide beam is between 60° to 120°.
Lights with narrow beam angle (spot lights) are usually used for spot lighting and for focusing your lighting to objects or certain areas. Narrow beam lighting is also used when the subject is far away from the light source.
Lights with wide beam angle (flood lights) are used for area lighting and studio lighting where uniformity of lighting is very important. Wide beam lighting is also used when the subject is near to the light source.
Two lights with same luminous flux (lumens) but different beam angles have different illuminance (lux). The light with the narrower beam angle will have more illuminance (lux) in a certain distance.
Lights with wider beam angle create wider beam width lighting.

Beam Width
Beam Width is the spread of the light in a certain distance from the light source. When the light hits to a wall it is measured by the width of the lighted surface. Light with wider beam angles create larger light beam widths in a certain distance from it.

Distance from surface
Distance from Surface is the distance between the light and the subject that is lighted.

The farther the subject is from the light source, the lower the illuminance (lux).
When the subject is away from the light source (more than 5m away), lights with narrow beam angle are preferred. When only flood lights are available, you can use lenses or reflectors which convert wide beam angles to narrow ones, increasing the illuminance (lux).
When the subject is near to the light source (less than 5m away), lights with wide beam angle are preferred. When only spot lights are available, you can use diffusers or softboxes to soften the lighting.

Luminous Flux (Lumens)
Lumen (lm) is a unit of measurement of the total power of visible light that is emmited from a light source. Luminous Flux. Just like watt is a unit of measurement of the power consumption of an electronic device, the number of lumens show us how powerful is a light - how much light power it emmits. (Energy/time or Watt/steradians or candelas⋅steradians).

Luminous Flux in Lumens is not affected from the beam angle of the light.
Luminous Flux in Lumens can be measured directly in front of the light source, in zero distance from it, before the light being spread to the area to different directions.
When a light source of one Candela Intensity is spread in all directions (a sphere), total luminous flux is 4π⋅cd⋅sr =12.5656 lumens.

Luminous Intensity (Candelas)

Candelas (cd) is a unit of measurement of the total power of visible light that is emmited from a light source per solid angle (steradian). Luminous intensity. So Luminous intensity = Luminous flux/steradian and cd=lm/sr. The number of candelas show us how powerful is a light talking in to consideration its beam angle.

Luminous intensity in Candelas is affected from the light beam angle.
Luminous intensity in Candelas is not affected from the distance between the subject and the light source.
Luminous intensity in Candelas can be measured directly in front of the light source in one steradian angle.
Luminous intensity in Candelas is a more efficient tool for comparing the power of light sources. When two lights with same Luminous Flux in lumens have different beam angles, the light with narrower light beam will have more Luminous intensity in Candelas.

Illuminance (Lux)

Lux (lx) is a unit of measurement of the total power of visible light that is emmited from a light source per square meter. Illuminance. So Illuminance =Luminous flux/square meter and lx=lm/m2. The number of lux show us how powerful is a light talking in to consideration its beam angle and at the same time the distance between the light and the subject. For example we usually say: illuminance at one meter is 2000 lux or illuminace at two meters is 1000 lux and we write: 2000lx @1m, 1000lx @2m.

Illuminance in Lux are affected from the beam angle of the light source and the distance between the subject and the light source.
Illuminance in Lux can be measured from a certain distance from the light source with a photometer.
Illuminance in Lux is the most efficient tool for comparing the power of light sources and the power of the incident light. When two lights with same Luminous Flux in lumens have different beam angles, the light with narrower light beam will have more Illuminance in Lux in certain a distance.
When two lights have same Luminous Flux in lumens and same beam angles, the light which is closer to the subject generates more Illuminance in Lux to the subject.

Illuminance (Foot candles)

Foot candles (fc) is a unit of measurement of the total power of visible light that is emmited from a light source per square foot. Illuminance. So Illuminance = Luminous flux/square foot and fc=lm/ft2. The number of foot candles show us how powerful is a light talking in to consideration its beam angle and at the same time the distance between the light and the subject. For example we usually say: illuminance at one foot is 2000 foot candles or illuminance at two feet is 1000 foot candles and we write: 2000fc @1ft, 1000fc @2ft.

Illuminance in Foot candles are affected from the beam angle of the light source and the distance between the subject and the light source.
Illuminance in Foot candles can be measured from a certain distance from the light source with a photometer.
Illuminance in Foot candles is the most efficient tool for comparing the power of light sources and the power of the incident light. When two lights with same Luminous Flux in lumens have different beam angles, the light with narrower light beam will have more Illuminance in Foot candles in a certain distance.
When two lights have same Luminous Flux in lumens and same beam angles, the light which is closer to the subject generates more Illuminance in Foot candles to the subject.