Moving Images, Understanding Media

Chapter 4 Storytelling with Light 129

Th e standard range of f-stops is: 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, and 22.

Each higher f-stop cuts the light by one half, and they are typically used with

increments of one-half or one-third between each standard f-stop number.

A low f-stop corresponds to a greater amount of light being allowed to pass

through the lens, while a high f-stop corresponds to a reduced amount of

light passing through the lens. Th us, in a dimly-lit scene, the f-stop might be

2.8, while a brightly lit exterior could have an f-stop of 22.

Shutter Speed and Frames per Second

Shutter speed is the length of time that the shutter on the camera is open

to allow light to pass into the camera and onto the light-sensitive surface.

On a camera, the standard shutter blade is a semi-circle shape so that as

it rotates it exposes then blocks the fi lm gate to control the light passing

through to the surface of the advancing fi lm. Normal camera speed for

Figure 4-9 Here, we are looking straight through a 50 mm lens: (a) the iris is completely open to an

f-stop of 2.0 for this lens. (b) the aperture is reduced one stop to 2.8 (c) the aperture is reduce two more

stops to 5.6. (d) the aperture only allows the small patch of white to be seen behind the lens when it is

set at f/22. Regulating the size of the aperture on a lens is one way to control exposure.

a

c

b

d

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