The Eye and Camera: Similarities and Evolution

The Eye and the Camera

• The eye and the camera share similarities such as having a lens, eyelid (shutter), pupil (aperture), and retina (light-sensitive surface).
• The eye is a product of organic evolution, while the camera is a product of electrical evolution.

Camera Defined and Evolution

• "Camera" originates from the Latin word for "Chamber".
• A camera is a light-tight box used to capture images by focusing light through a pinhole or lens onto a sensitized material, with a shutter controlling light exposure.

Essential Parts of a Camera

• Light Tight Box: Enclosure that blocks extraneous light from reaching the film before and after exposure.
• Lens: Focuses reflected light from an object to form a sharp image on the film.
• Shutter: Controls the duration of light exposure on the film.
• Holder of the Sensitized Material: Keeps the film firmly in place during exposure.
• Viewfinder: Determines the camera's field of view.

Lens Types and Function

• Lenses focus light rays to create sharp images on the film.
• Convergent/Positive/Convex Lens: Thicker at the center, bends light inward, and produces a real image.
• Divergent/Negative/Concave Lens: Thinner at the center, bends light outward, and produces a virtual image.

Focusing Methods

• Focusing involves setting the proper distance to form a sharp image.
• Scale Bed/Focusing Scale: Uses a scale on the lens barrel with pre-set distances for focusing based on estimated or measured object distance.
• Rangefinders: Measure the angle of light convergence to determine focus.
  • Split Image: Divides the object's image into halves that align when in focus.
  • Coincident/Double Image: Shows a doubled image that coincides when in focus.
• Ground Glass: Focuses by directly observing the image on a screen behind the lens.
• Zone: Uses preset focus settings for close, medium, and distant objects, typically with wide-angle lenses.

F-Numbers/F-Stops and Depth of Field

• F-numbers indicate a lens's light-gathering power, controlled by a diaphragm.
• Depth of Field: Zone of acceptable focus, from the nearest to the farthest sharply focused object.
• Increased depth of field: Shorter focal length, small lens aperture, greater subject distance.
• Decreased depth of field: Longer focal length, larger lens aperture, shorter subject distance.

Circle of Confusion and Depth of Focus

• Circle of Confusion: Describes sharpness, aiming for a tiny point on the subject to be a tiny point in the image.
• Depth of Focus: The amount the film plane can move without blurring the image, assuming the subject is stationary.

Hyperfocal Distance

• Hyperfocal Distance: The closest distance at which a lens focused at infinity provides maximum depth of field.

Lens Classification by Focal Length

• Focal Length: Distance from the lens's optical center to the film plane when focused at infinity, measured in millimeters.
• Wide-Angle Lens: Focal length shorter than the negative material's diagonal, providing a wide field of view with low magnification (14mm–35mm).
• Characteristics of Wide-Angle Lens: Reduced scale, increased area, increased depth of field, distortion at edges, reduced illumination toward edges.
• Fisheye Lens: Extreme wide-angle lens, up to 180-degree view, with focal lengths of 8mm-10mm, significant image distortion.
• Normal Lens: Focal length approximately equal to the negative material's length (45-55mm), offering realistic views with minimal distortion.
• Long/Telephoto Lens: Focal length equal to or more than twice the negative material's diagonal, narrow angle of view, great magnification.
• Characteristics of Long or Telephoto Lens: Decreased depth of field, increased scale, reduced area, angle of view less than 45 degrees, image quality can deteriorate if subject is in motion.
• Zoom Lens: Variable focal length, allowing quick focal length changes without swapping lenses.

Inherent Lens Defects

• Spherical Aberration: Light rays focus at different points, resulting in a distorted, fuzzy image.
• Coma/Lateral Spherical Aberration: Angled light rays cause blurred, comet-shaped images for off-axis points.
• Chromatic Aberration: Color fringing around edges due to the lens's inability to focus all colors at the same point.
• Curvature of Field: A curved lens distorts the image onto a curved plane instead of a flat one.
• Astigmatism: Light focuses into lines or ellipses instead of points, occurring with wide fields or angled light.
• Distortion: Alters the shape of the image, making straight lines appear curved due to varying focal lengths.
  • Positive/Pincushion Distortion: Image points displaced outward from the center.
  • Negative/Barrel Distortion: Image points displaced inward toward the center.

Lens Correction Degrees

• Achromatic Lens: Corrected for Chromatic Aberration.
• Rapid Rectilinear Lens: Corrected for Distortion.
• Anastigmat Lens: Corrected for Astigmatism.
• Apochromatic Lens: Corrected for Astigmatism with higher color correction.
• Aspherical Lens: Corrected for Spherical Aberration using a non-spherical lens element to focus light at the film plane.

Shutter Types and Function

• Shutter: Blocks light from the lens, exposing the film for a set time.
• Central Shutter: Located within the lens, metal leaves that open from the center and close back to the center.
• Focal Plane Shutter: Located near the film, typically a cloth curtain or metal, moving vertically or horizontally to control exposure.

Shutter Speed

• Shutter Speed: Controls the duration of light exposure, adjustable via a selector, with standard settings like 1, 1/2, 1/4, up to 1/2000.
• B-Setting: Keeps the shutter open while the button is pressed.
• T-Setting: Opens the shutter with one press and closes with another.

Film Holder

• Film Holder: Secures the film during exposure to prevent blur.

Additional Camera Parts

• Viewfinder: Shows the scene that will be recorded.
• Film Advancer: Moves exposed film and prepares new film for exposure.
• Lens Aperture: Controls the amount of light entering the lens.
• Shutter Speed Selector: Adjusts the shutter's opening and closing speed.
• Focusing Mechanism: Provides image sharpness.

Camera Accessories

• Tripods: Stabilize the camera, eliminating shake and locking in composition.
• Cable Release: Fires the camera remotely to avoid movement during longer exposures.
• Flash Units: Provide additional light, synchronize with the shutter, and freeze motion.
• Light Meter/Exposure Meter: Measures light intensity to determine correct exposure.
  • Extinction Meter: Estimates light by observing shadows.
  • Photoelectric Meter: Converts collected light into electrical energy for a meter reading.
• Extension Tubes: Increase the lens-to-film distance for magnified close-up shots.
• Camera Grip: Holds the camera firmly to prevent vibration.
• Lens Hood: Prevents extraneous light from causing flare.
• Filters: Transparent media that transmit and absorb different light wavelengths, and alter light characteristics.
• Types of Filters:
  • Correction Filter: Adjusts film response for accurate color recording.
  • Contrast Filter: Changes brightness to create tonal differences.
  • Haze/UV Filter: Reduces atmospheric haze.
  • Neutral Density Filter: Reduces light uniformly without changing color.
  • Polarizing Filters: Reduce reflections from reflective surfaces.

Camera Types

• Viewfinder Camera: Simple, compact, inexpensive, suffers from parallax error, limiting close-up photography.
• Single Lens Reflex (SLR): Uses a mirror to allow viewing and focusing through the same lens, eliminating parallax error, ideal for police work and precise framing.
• Twin Lens Reflex: Uses two lenses, one for viewing, and the other for taking image, suffers from parallax error, and projects a reversed image.
• View/Press Camera: Large, sophisticated, uses a viewing screen, does not suffer from parallax error, useful for document reproduction and photomicrography, bulky and unsuitable for action shots, and projects an upside-down image.