Optics and Depth of Field

Your Lens

•Your lens is made up of curved glass that is moved when you focus and zoom

Focal Length

• Focal length refers to the strength of magnification by a lens

24mm

50mm

200mm

800mm

Focal Length and Angle of View

• The Shorter the Focal Length the wider the angle of view

Other features of focal length

• Short Focal length = wide angle– Wide angle lenses tend to distort objects

especially if they are close to the lens

• Long focal length tends to compression image

Wide Angle Distortion

Wide Angle Distortion

Long Focal Length/Telephoto Compression

Telephoto Compression

Special Lenses

Tilt Shift Lens

Tilt Shift

Tilt Shift

Lensbaby

Fisheye

Fisheye

Depth of Field

• The portion of a scene that appears sharp in the image

• A lens can precisely focus at only one distance, but the decrease in sharpness is gradual on either side of the focused distance

• Not easily perceived by the human eye

Long/Deep Depth of Field Shallow Depth of Field

Depth of Field is Controlled by Three Things

1. Aperture

2. Focal Length-zoom

3. Closeness of subject to camera

Controlling Depth of Field with Aperture

• A low aperture (1.8 to 5.6) gives you low.short/shallow depth of field

• A high aperture (11-32) gives you a long/deep depth of field

F 3.5

F 22

Controlling Depth of Field with Focal Length

• Longer lenses tend to give you a shorter depth of field resulting in blurrier backgrounds

• Wider lenses are better at keeping more depth in focus

Controlling Depth of Field with Proximity to Subject

• Similarly, the closer you are to the object the less depth of field will be present

• This is the same idea as focal length

More Examples

DOF

Low DOF

Low DOF

Low DOF

Low DOF

Low DOF

Long DOF

Long DOF

Long DOF

Long DOF

Long DOF