Useful tips

# How do you calculate illuminance?

## How do you calculate illuminance?

The equation of the illuminance, E, of a small light source is E = P/ 4(pie)d^2, where P is the luminous flux (in lumens, lm) of the source and d is its distance from the surface.

### What is the formula for lux?

One lux is equal to one lumen per square metre: 1 lx = 1 lm/m2 = 1 cd·sr/m2. A flux of 1000 lumens, spread uniformly over an area of 1 square metre, lights up that square metre with an illuminance of 1000 lux.

#### How does illuminance change with distance?

There is an inverse relationship between distance and light intensity – as the distance increases, light intensity decreases. This is because as the distance away from a light source increases, photons of light become spread over a wider area.

How is illuminance and luminance calculated?

Illuminance (lux) x reflectance = luminance (apostilbs).

How is maximum illuminance calculated?

Thus, by using the formula, we can calculate U1 = Minimum / Average lux = 551 / 624 = 0.88, and U2 = Minimum / Maximum lux = 551 / 708 = 0.78….3. How to Calculate Lighting Uniformity.

Value Illuminance
Maximum 708 lux

## What is the SI unit of illuminance?

Lux
Lux (abbreviation lx): The SI unit of illumination value; it is equal to one lumen per square metre.

### What does 1 lux look like?

A measurement of 1 lux is equal to the illumination of a one metre square surface that is one metre away from a single candle. The diagram below helps to visualise this more easily….Definition of Lux.

Natural Light Condition Typical Lux
Sunset & Sunrise 400
Moonlight (Full moon) 1
Night (No moon) < 0.01

#### How many lux is a 60 watt bulb?

How Much Light Do I Need?

Old Incandescent Bulbs (Watts) ENERGY STAR Bulb Brightness (Minimum Lumens)
40 450
60 800
75 1,100
100 1,600

What is the unit of illuminance?

Does distance affect luminosity?

The difference between luminosity and apparent brightness depends on distance. If you put an automobile headlight 10 feet away and a flashlight 10 feet away, the flashlight will appear fainter because its luminosity is smaller. Stars have a wide range of apparent brightness measured here on Earth.

## How do you find the minimum and maximum illuminance?

### What is the equation for point source illuminance?

It is the point source Illuminance equation. Where, I θ is the luminous intensity of the source in the direction of the illuminated point, Ɵ is the angle between the normal to the plane containing the illuminated point and the line joining the source to the illuminated point, and d is the distance to the illuminated point.

#### How to graph a function in equation Grapher?

If you just want to graph a function in “y=…” style you may prefer Function Grapher and Calculator Use the zoom slider (to the left zooms in, to the right zooms out). To reset the zoom to the original bounds click on the Reset button. Click-and-drag to move the graph around.

What is the inverse square law of illumination?

The Inverse Square Law of Illuminance This law states that the Illuminance (E) at any point on a plane perpendicular to the line joining the point and source is inversely proportional to the square of the distance between the source and plane. Where, I is the luminous intensity in a given direction.

How is illuminance related to the square of the illuminated point?

It is seen that Illuminance varies inversely as the square of the illuminated point from the source. If the light source is not a point source, then we can assume this large source as the summation of many point sources. This relationship can be applied to all light sources.