Post on 14-May-2015
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
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