Optics and Depth of Field
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