In Episode 2, I explained how the aperture is the mechanism inside the camera, also called the diaphragm, that allows you to change the amount of light entering the camera through the lens by changing the size of opening. This is called the lens aperture. This lens aperture is what dictates the depth of field.
What is Depth of Field? Depth of Field is the front-to-back zone within which objects appear sharp.
When there is very little in focus, you have shallow DOF.
When you have wide or great DOF, lots or everything in the image is sharp.
DOF is controlled by 3 factors working together.
1) f/stop (lens aperture)
2) distance from camera to subject
3) focal length of lens
Let’s take a look at the f/stop number and it’s direct connection to DOF:
A smaller aperture, which is a big f/number, such as f/22 but has a small opening letting in less light, resulting in greater DOF
A large aperture, which is a small f/number, such as f/2.8 has a large opening letting in more light, and has a narrow or shallow DOF, with only a small zone of front-to-back that is in focus.
In the next episode, we’ll take a look at how the focal length of the lens can affect the DOF.