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• Lens


  The basic function is to gather light rays from a subject, form and focus those rays into an image, and project this image onto film inside the camera
• Optical glass


  • Can bend or change the direction of light rays that pass through it
  • When shaped with concave or convex surfaces, light rays may be directed up, down, or straight, depending on the configuration of the lenses
• Lens


  A system of one or more pieces of glass bounded by spherical surfaces, the center of which is at a common axis, termed the lens axis
• Lens


  A mechanism or system which converges or diverges light passing through it to form an image
• Two Main Types of Lenses According to Shape

  • Convergent/Positive/Convex Lens
  • Divergent/Negative/Concave Lens
• Convergent/Positive/Convex Lens


  • Thicker at the center and thinner at the sides
  • Light passing through it are bended toward each other on the other side of lens meeting at a point
  • Produces a real image on the opposite side of the lens or where light is coming from
• Divergent/Negative/Concave Lens


  • Thinner at the center and thicker at the sides
  • Light passing through it are bended away from each other as if coming from a point
  • Produces a virtual image on the same side of the lens or where light is coming from
• Lens Characteristics


  • Focal length
  • Relative aperture
  • Depth of field
  • Hyper focal distance
  • Focusing
• Focal length


  The distance measured from the optical center of the lens to the film plane when the lens is set or focused at infinity position
• Types of Lenses According to Focal Length

  • Wide-angle lens
  • Normal lens
  • Long or Telephoto lens
• Relative aperture


  The light-gathering power of the lens expressed in the F-number system
• Relative aperture


  • Controlling the amount of light passing through the lens
  • Controlling the depth of field
  • Controlling the degree of sharpness due to lens defects
• Depth of field


  The distance measured from the nearest to the farthest object in apparent sharp focus when the lens is set or focused at a particular distance
• Hyper focal distance


  The nearest distance at which a lens is focused with a given particular diaphragm opening which will give the maximum depth of field
• Focusing Methods


  • Focusing scale or scale bed
  • Range-finders
• Focusing scale or scale bed


  A scale on the lens barrel indicating pre-settled distance in feet or meters
• Types of Range-finders


  • Split-image
  • Co-incident image
• Lens Defects


  • Astigmatism
  • Coma
  • Curvature of Field
  • Longitudinal Chromatic Aberration
  • Lateral Chromatic Aberration
  • Spherical Aberration
  • Distortion
  • Flare
• Astigmatism


  The lens is unable to bring both vertical and horizontal lines into focus on the same plane, caused by axial rays
• Astigmatism


  • Can be mitigated by stopping down the lens (using a smaller lens opening, resulting in a larger F number)
• Coma


  Distorts parallel oblique rays passing through the lens, resulting in an image that is not focused as a point but rather as a comet-shaped (oval) image
• Coma


  • Stopping down the lens can help improve coma
• Curvature of Field


  The plane of sharpest focus becomes curved instead of flat, caused by rays from the outer limits of the subject plane coming into focus nearer to the lens than the axial rays
• Stopping down the lens does not improve curvature of field
• Longitudinal Chromatic Aberration


  The lens's inability to focus all colors (wavelengths) at the same plane on the lens axis
• Longitudinal chromatic aberration is not improved by stopping down the lens and is typically more noticeable in long telephoto lenses
• Lateral Chromatic Aberration


  The lateral displacement of color images at the focal plane, occurring due to the different sizes of images produced by different colors, even though all the images are on the same plane
• Lateral chromatic aberration results in color fringing, typically red or blue, and is not improved by stopping down the lens
• Spherical Aberration


  The inability of all rays to focus at the same point, where marginal rays come to focus closer to the lens than paraxial rays
• Distortion


  Causes the image of a straight line, particularly at the edges of the field (CCD), to bow in or out, resulting in pincushion distortion (bowed in) or barrel distortion (bowed out)
• Distortion is not improved by stopping down and is common in extreme wide-angle lenses and lenses with wide-angle adapters
• Flare


  Non-image-forming light that reduces contrast and color saturation, caused by very bright subject areas and resulting in internal reflections within the lens
• Flare does not affect sharpness but can alter the shape of the image, and is not improved by stopping down
• Special Types of Lenses

  • Macro Lenses
  • Zoom Lenses
• Macro Lenses


  Designed with extended focusing capabilities to shoot a few inches from the subject
• Types of Macro Lenses

  • Hand-held tripod mounted camera lenses (40mm to 90mm)
  • Wide angle or longer lenses (100mm or more) with close-up bellows attachment
• Zoom Lenses


  Allow quick adjustment to give a wide or narrow field of vision, by moving back and forth while other elements stay in place
• Camera Parts and Features

  • LCD Display
  • Viewfinder
  • Power Switch
  • Cross Keys
  • Erase Button
  • Play Button
  • Lens
  • Lens Release Button
  • Flash Button
  • Lens Focus Mode Switch
  • Flash
  • Mode Dial
  • Main Dial
  • Shutter Button
• LCD Display


  A screen on the back of the camera that displays various settings, menus, and images captured by the camera
• Viewfinder


  An optical or electronic device located at the top of the camera, which allows the photographer to frame and compose the shot by looking through it