Photographers who have a little knowledge about elementary physics would surely have a clue about the inverse square law. The inverse square law in physics is being used for various physical entities like gravitation, electrostatics and light. It is useful to know about the inverse square law of light for photography, especially while using flash or studio lights. The inverse square law basically states that the intensity of light from a point source of light is inversely proportional the square of its distance from the subject.

To explain the law more clearly, with increasing distance from a point source of light, its intensity decreases by the square of the increase in distance between the light source and the subject.

Now if you see the image, you can see that as the distance increases the light coming from the light source fans out quickly. The object that is closer to the source is receiving more concentrated light than the farther one. So if the second object is kept at double the distance from light source, as compared to the 1st object, then the 2nd object receives 1/4th of the light received by the first one. This is because, according to the inverse law the distance is double and square of 2 is 4; hence the intensity of light being inversely proportional to the square of distance will be 1/4th.

Now the reason why photographers need to study this is because it might become necessary for them to adjust the camera’s exposure settings, based on the amount of light on in the object. Digital cameras, like the Samsung S760, typically take care of this automatically, but if you are shooting on manual you will need to know in a studio with a fixed point source, then you will need to adjust your aperture depending on the distance to the object. If you do need to shift position, then with each fold that you move closer to or farther away from the light source, you will have to open or close your aperture with as many stops.