Aperture

Aperture is:

Put simply, a hole that allows light to reach the recording medium. It can get larger or smaller in nearly all lenses.

Aperture controls:

First and foremost, the aperture’s main function is to control the amount of light entering the camera by increasing or decreasing the size of the hole.

Depth of Field:

Aperture is one way to control depth of field. The larger the aperture, the more shallow the depth of field will be. The smaller the aperture, the deeper the depth.

Camera Obscura

The Camera Obscura is simply a light tight box with a hole opposite of the recording medium. Occasionally, they may have a lens.

Aperture basics

In week one, we turned the entire room into a Camera Obscura, a primitive camera. The windows and doors were blackened with paper and a large hole was cut into the paper covering the window.

This large hole was our aperture.

We used an old screen printing silk to project the image onto so that students could see how the image changed. Using pieces of paper with smaller and smaller holes, students could watch the resulting projected image become sharper yet more dark each time the hole diameter was decreased.

See the photos below for reference:

F-Stops

F-stops is the function of the lens’ focal length divided by the physical diameter of the aperture. For instance, a 500mm lens with a 50mm aperture diameter will be at f/10. A 200mm lens with a 50mm aperture diameter will be at f/4.

F-stops do not change between lenses. What I mean by that is if you have a 28mm lens at f/10 and a shutter speed of 1/60 and you change to a 300mm lens, your settings will not need to be changed (f/10, 1/60th). {note, this may not be exactly accurate because of light transmission properties or T-stops}.

F-Stop

Focal length/aperture diameter = f-stop number and are interchangeable between lenses

Depth of Field

Depth of Field (DoF) refers to how much of an image is in focus from near to far.

Depth of Field as it Relates to Apertures

A large aperture diameter (or lower f-stop number) will let in more light but the image will have a very narrow depth of field. Conversely, a small aperture diameter will create a deeper depth of field but will allow less light to reach the recording media.

For instance, if you are shooting a group of eight people, you will need a deeper depth of field to get them all in focus (a good rule of thumb for group numbers is f-stop = the number of people in the photo). If you are photographing a single person and want to isolate them from the background, a wide aperture will blur the background (bokeh) but keep the person in focus.