You cannot place a new order from your country. United States

 By: Jo Chew
Date: 7/4/2005

Cameras usually carry a Lux rating, which determines how sensitive the camera is to low light conditions. Here I will ‘shed some light’ on the matter.

What is light?
Light is a form of electromagnetic radiation. The human eye is very sensitive towards this radiation, and the various frequencies that our eyes interpret as colours. Electromagnetic radiation comes in different wavelengths. The electromagnetic spectrum is very large, and human visible light is only a tiny fraction of the spectrum. The window of human visible light, is roughly 400nm to 700nm.

Light & Lux

The human eye
In the human visible 400nm to 700nm range, 400nm corresponds to violet, and 700nm to the colour red. There is actually a continuous change from violet, blue, green, yellow, orange to red, as the wavelength increases. You can see this in the diagram above.

The color green, excites the eye the most. This means, if we have all the wavelengths of the light with an equal amount of energy, green will produce the highest output on the retina.

Frequencies below 400nm or above 700nm are not able to be seen by the average human eye. Average because everybody is different. People who are colour blind can't see certain colors. Whereas an artist or photographer might develop a sensitivity towards frequencies (colors) which may look the same to another person. It is possible some people may even extend their minimum and maximum detectable limit.

It is interesting to note other animals, such as the cat family, who are known for having good night vision. Which would mean they can see beyond the 700nm range of humans, which makes them sensitive to infrared light.

How is light measured?
You always see that cameras have a Lux level. The way lux is calculated is actually rather technical, it is roughly the amount of light created by a candle at a distance of 1 meter. To provide some typical light levels:

100000 Lux – Sunny day
10000-100000 Lux – Sunny day with some clouds
100-10000 Lux – Overcast sky
100-1000 Lux – Home/Office lighting
1-10 Lux – Street lighting
0.1 Lux – Full moon
0.01 Lux - Young moon
0.001 Lux – Clear night without moon
0.0001 Lux – Dark cloudy night

Keep in mind that black and white cameras will function better in low light conditions. Colour cameras will start to give a grainy image as light levels drop.