Inverse square law & lighting techniques

Inverse square law
The inverse square law says that an object that is twice the distance from a point source of light will receive a quarter of the illumination. What this means is that if you were to move your subject from 3 meters to six meters away that you would need four times the amount of light for the same exposure. To achieve this you can open the lens aperture by two f-stops. According to the law, the power of the light will be inversely proportional to the square of the distance.
DSC_0196_edited-1 DSC_0201_edited-1

As you can see the char closest to the light source is correctly exposed and as the chairs get further away from the light source the darker they appear. The first chair is correctly exposed at f/5.6 so for the middle chair I would need to open my lens aperture by 2 f-stops or change my ISO from 400.~
DSC_0209_edited-1 DSC_0210_edited-1 DSC_0211

The law didn’t appear to work for these images in this scenario. I don’t think the law worked for these images because the lighting wasn’t from one single spot, it was from all of the windows as well as the lights down the corridor.

Lighting Techniques


In this image the light source is quite a distance away from the subject causing them to cast a large shadow. Because the light source is further back it allows it to spread all over the subjects causing their left side and some of their right side to become illuminated.

In this image the light source is closer but not directly pointing at the subject and because the wall is black no light is reflected back. The subjects have a much shorter shadow as the light source is much closer.

The light appears on the wall in a long long line because the shutter was open for a long amount of time while the light source was moved up and down next to the subject. This technique is known as painting with light/light painting.

This image was created by using a phone torch as the only source of light and moving it all over the subjects in a circular motion which has created a faint glow around the subjects. This is able to be seen because of the low shutter speed I have used which has allowed the camera to pick up the movement of the light.


These images were created by using a phone torch and moving it around on the left side of the subjects. The torch has created a faint line of light on the side it was moved around on and has illuminated the subjects enough so they can be seen clearly. On the first image  the phone light appears like it moved in a faster rate than the second image as the light is spread far less on the second image.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s