Photography Snapshot: Why is Light Important?

Experiments GeekMom Technology
Lego Pinhole Camera from andeecollard flickr photo stream. (CC BY-SA 2.0)

In an effort to learn how to take beautiful photos of my family and friends, I’ve spent the last six months learning as much as I can about photography. As you might imagine, the basics weren’t enough for a geekmom, so I dug into the science behind the photography.

Over the next few weeks, I’m going to share a number of lessons dealing with the essentials of photography, some of the science behind the images, and products that are likely to make your pictures easier or better. This first lesson will deal with the basic properties of light and the most basic ways to capture that light. Future lessons will talk about the exposure triangle: aperture, shutter speed and ISO.

Light is everywhere, even in the darkest recesses of space. There are a few basic properties of light that are important for photographers to remember while they are composing scenes. These principles are straightforward and it’s likely that you learned most of them in basic high school level science classes.

  • Light can only be seen if it reflects off of something or if we are looking directly at the original source.
  • Light can be reflected(bounced) or refracted(bent) in very predictable ways.
  • The roughness of a surface determines the amount that light will scatter after it bounces.
  • White light is made up of all of the visible colors combined.
  • Light is measured in by its energy level or wavelengths. Different colors are denoted by their wavelengths.
  • Shadows occur when something falls within the direct path of a light source and ourselves.
  • The human eye is amazingly versatile at adapting to differing brightness levels, far more effective then even the most advanced cameras.
Light from the sun turns into diffuse light when bounced off objects.

The basic idea of photography is turning light into an image. Of course creating an image is easy in theory. In practice, however, the art and science of photography is getting the image to look the way you predict regarding focus, brightness and depth of field. An image is actually an illusion, a representation of the external form of a person or thing. So the problem is: how do we turn randomly scattering light into a recognizable image.

Imagine looking at a stack of legos outside on a completely sunny day. The light that comes from the sun in the direction of the legos will reflect off the surfaces in all sorts of directions creating diffuse light.
Reflected light creates an image when projected through an aperture.

Now imagine standing in a box made of a completely light proof material. Lets assume that the box happens to have a pin point size hole in the side.

When a single ray of light come from the sun, that single ray will hit an object the light will scatter in all sorts of directions. one of those directions will be toward the pin sized hole in the box. That hole will only let a small ray of light through. When rays from an object all bounce toward that pin point hole, some will pass right through on the same path that they started on. The collection of rays will create a focal point at the location of that hole and at some distance behind the focal point an image will form. That distance is a ratio of the distance to the object in question and the size of the hole. The rays that pass directly through the hole, create an image that is upside down.

That box that we imagined is actually called a camera obscura and is one of the most primitive forms of photography.  You can create your own pinhole camera exactly as described above or turn an entire room into a camera obscura.

  1. Find a room in your house that only has one window.
  2. Cover that window with cardboard or foil.
  3. Put a 1-5mm hole in the foil.
  4. Look at the opposite wall. What do you see?
Assuming you followed the directions properly, the image you see on the wall will likely be an upside down version of the world outside. Since it is very unsafe to view the sun directly, the camera obscura is the safest method to observe the sun, especially during a solar eclipse or when viewing sun spots. The image will be pretty dim compared to the original object because the hole is so small and so few rays of light can pass through. However, while enlarging the hole will let more light in, it will also cause your image to become fuzzy since there are so many more directions that scattered light can pass through the hole.
This shows how the size of the hole, or aperture, effects the sharpness of an image.

A pinhole camera is a very simple version of this type of camera. The only difference between a camera obscera and a pinhole camera is that there is some additional element in the camera that captures the created image.  If you would like to create a pinhole camera, put a piece of light sensitive or photographic paper into the location where the image forms.

So how is any of this relevant to photography?

The tradeoff of sharpness or brightness is the everyday plight of a photographer. Every image is a balancing game between balancing the perfect amount of light with the sharpness of the image. The hole in the camera obscura is known as an aperture in any camera system. As the aperture of a camera increases in size, more light enters the optical system, but the depth of field decreases and the image will fall out of focus.

We will talk more about all of these elements and their specific relation to photography, we will cover each of these in depth over the next few weeks.

If you have a chance to create a pinhole camera, post a link with a picture you take! Only have a chance to create a camera obscura? Take a picture and share it with us, lets go through this photography journey together!

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