Principles of Photography

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Principles of Photography
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Principles of Photography

• What is photography, and how are photographs
  made?
• Photographs are captured moments in time.
• Photographs are made with Light, Camera, Film and
  Knowledge.

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What is Light, and why is it important
to photography?

• Light is a form of energy released by the sun or
  man made sources.
• Without light, the chemical reaction necessary in
  forming images on a piece of acetate (film) or
  within a digital imaging camera cannot take
  place.

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Electro Magnetic Spectrum

• - The Sun releases various wavelengths of energy,
  which are measure in nanometers.

VISIBLE LIGHT
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Visible Light

• Light propagates as a wavelength and is
  characterized by the length between two peaks.

0.0000000001 meters ( 10 -9 m in scientific
notation )
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White Light

• The three primary colors (Red, Green and Blue)
  when evenly mixed produced white light.
• The three primary, or additive colors also
  produce other colors when equally mixed or
  unequally.

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Light Sources

• Daylight
• Electronic Flash
• Fluorescent
• Tungsten
• Metal Halide, Sodium or Mercury Vapor
  Illumination
• Alternate Light Sources

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Kelvin Temperature

• All light sources have temperatures, which are
  measured on a color temperature scale.
• The color temp. scale is known as the Kelvin
  scale.

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Daylight Balanced Film

• Color films are normally balanced for only
  Sunlight or Flash photography.
• If Daylight balanced film is used with the
  artificial lighting, true color rendition is
  more difficult to achieve.

Daylight film with tungsten lighting.
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Film Pages 8-11
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Types of Film

• Negative
• Positive (transparency)
• Instant
• Digital

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Film

• Film comes in a variety of ISOs.
• Fast speed films
• Medium speed films
• Slow speed films

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Film and Film Speed

• EI Exposure Index (100 is the rating)
• ASA American Standard Assoc.
• ISO International Standards Org.
• DIN Deutsche Industrie Normen

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What is ISO?
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Film and Film Speeds

• Film with lower ISOs (25, 64, 100 and 200) are
  less sensitive to light, and therefore need more
  light. These films are called slow films.
• Film with higher ISOs (400, 800, 1000, P3200)
  are more sensitive to light. These films are
  called fast films.

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Film and Film Speeds

• The most popular ISOs are 100, 200 and 400.
  However, there are a variety of ISOs available
  for differing conditions and applications.

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Film

• HOW DOES THE FILM RECORD THE IMAGES WE SEE?

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What is film, and how does it work?

• Film is several layers of acetate sandwiched
  together. One layer, the emulsion layer, contains
  silver halide crystals (bromine, iodine or
  chlorine).

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Silver Halide Crystals

• Silver halide crystals upon exposure to light
  darken and form a latent image. Upon
  development, a permanent negative or positive
  image is formed.

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Silver Halide Crystals

• The amount of grain, and the size of the grain
  effect the sensitivity of film to light. Grain
  also effects the quality of the print to be
  produced from particular films.

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Film ISOs (Full Stops) Page 8

• 12
• 24 (25) (2x sensitivity)
• 50 (2x sensitivity)
• 100 (2x sensitivity)
• 200 (2x sensitivity)
• 400 (2x sensitivity)

• 800 (2x sensitivity)
• 1600 (2x sensitivity)
• 3200 (2x sensitivity)
• 6400 (2x sensitivity)
• 12800 (2x sensitivity)
• 25605 (2x sensitivity)

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Film Latitude

• The ability of a light sensitive material to
  compensate for over and under exposure
• BW films have the greatest exposure latitude.
  Typically, BW films can reproduce acceptable
  positive prints from up to 4 stops underexposed.
• Color negative films do not have the same
  latitude as BW films. However, acceptable
  prints can be made from up to 2 or 3 stops
  underexposed.

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What is over and under exposure?

• Over-exposure is when a light sensitive material
  receives too much exposure. Resulting in dense
  negatives with opaque highlights and blocked up
  shadows.
• Under-exposure is when a light sensitive material
  receives too little light. Resulting in a thin
  negative, a dark slide or a muddy (grayish)
  looking print.

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Film Storage

• Film must be stored in a cool, dry place.
• Long term storage in a freezers.
• Short term storage in a refrigerator.
• Never store film in direct sunlight, or in areas
  that have constant temps above 60 degrees.

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Evaluating Negatives

• Dark areas in a negative will appear lighter on
  the print, and light areas of the negative will
  be dark on a print. Always evaluate a negative
  by the amount of detail in the shadow areas.

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Exposure

• What is exposure?
• The amount of light reaching a light sensitive
  material specifically, the intensity of light
  multiplied by the time light falls on a material.
  
• What controls exposure?

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Exposure Controls

• Light (Quality and Quantity)
• Film (Sensitivity)
• Diaphragm (Aperture-F/Stops)
• Shutter Curtain (Speeds)

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Exposure Controls - Light

• Remember, film needs light in order to create an
  image.
• The amount/type of light present determines how
  much exposure in needed to create an acceptable
  image.

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How can light intensity change?
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Inverse Square Law

• Illumination intensity on a surface will vary
  inversely with the square distance from the light
  source to the illuminated surface
• In other words, as light travels in distance, the
  intensity of the light source diminishes.

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Diaphragm

• The diaphragm controls the amount of light that
  penetrates through the lens.
• The F/stop ring on lens controls the size of
  opening of the diaphragm.
• The relative size opening of the diaphragm is
  called the aperture. The aperture size is
  expressed in fractions, known as F/stops

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Aperture
Maximum Aperture Minimum Aperture
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Aperture

• The lower the F/stop number, the wider the
  diaphragm opening on the lens. This wider
  opening allows more light to make exposures.
• The widest opening of a given lens is called the
  maximum aperture.

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Aperture

• The higher the F/Stop number, the smaller the
  diaphragm opening in the lens. This smaller
  opening allows less light to make exposures.
• The smallest opening of a given lens is called
  the minimum aperture.

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F/Stops or Aperture Sizes (Full Stops) Page 24

• 1.0 (widest opening)
• 1.4 (1/2 amt. of previous)
• 2.0 (1/2 amt.)
• 2.8 (1/2 amt.)
• 4.0 (1/2 amt.)
• 5.6 (1/2 amt.)
• 8.0 (1/2 amt.)
• 11 (1/2 amt.)
• 16 (1/2 amt.)

• 22 (1/2 amt.)
• 32 (1/2 amt.)
• 45 (1/2 amt.)
• 64 (1/2 amt.)
• 90 (1/2 amt.)

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Depth-of-Field

• The diaphragm also controls depth- of- field.
• D.O.F. is the area of acceptable sharpness in an
  image.

F/2.8
F/22
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Depth of Field

• Three things control depth of field
• Aperture size
• Lens Focal Length
• Lens to subject distance

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Depth of Field
F/2

• F/stops such as F/1.4, F/2.0, F/2.8, F/3.5...
  etc., allow more light to enter through the lens,
  but give shallow depth of field.

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Depth of Field
F/16

• F/stops such as F/11, F/16, F/22 etc., allow
  less light to enter the lens, but give greater
  depth of field.

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Depth of Field
Same F/stop setting was used on all three lenses.
Note the difference in depth of field.
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The Shutter Curtain Pages 27-29

• The shutter controls the amount of light that is
  to pass through the camera body.
• Similar to the diaphragm, the shutter is
  controlled by the photographer. The shutter
  allows the photographer to give more or less
  exposure to the film when needed.

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Focal Plane Shutters
Focal Plane Shutters are located directly in
front of the film in the back of the camera.
Focal plane shutters can move either horizontally
or vertically.
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Shutter
Leaf shutters are located inside of the lens.
Leaf shutters are limited in shutter speeds when
compared to focal plane shutters.
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Shutter Curtain

• At lower shutter speeds, i.e... 1/15, 1/30, 1/60
  of a second, more light is exposed to the film.

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Shutter Speeds (Full Stops) Page 28

• 1 Second
• 1/2 (Sec.) (1/2 amt.)
• 1/4 (Sec.) (1/2 amt.)
• 1/8th (Sec.) (1/2 amt.)
• 1/15th (Sec.) (1/2 amt.)
• 1/30th (Sec.) (1/2 amt.)
• 1/60th (Sec.) (1/2 amt.)
• 1/125th (Sec.) (1/2 amt.)
• 1/250th (Sec.) (1/2 amt.)

• 1/500th (Sec.) (1/2 amt.)
• 1/1000th (Sec.) (1/2 amt.)
• 1/2000th (Sec.) (1/2 amt.)
• 1/4000th (Sec.) (1/2 amt.)
• 1/8000th (Sec.) (1/2 amt.)

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Shutter Speeds (Stopping Motion)

• The shutter also controls motion. That is, the
  shutter determines how much motion is to be
  stopped. The higher the number (1/125, 1/250,
  1/500 etc..), the more motion will be stopped.

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Shutter Speeds (Stopping Motion)
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Reciprocity Law

• Time (T) x Intensity (I) Exposure (E)
• If the time is doubled and the intensity is cut
  in half (and vice versa), the exposure remains
  the same.
• Your camera has control equivalents for exposure
  control. When used together properly proper
  exposure can be achieved.

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Reciprocity Law Failure

• The balance of exposure as you change either the
  f/stop or shutter speed.
• One requires the reciprocal change of the other.
• Failure occurs more frequently at long or short
  exposure times.

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Exposure Review

• The intensity of light and length of time that
  light is subjected to a piece of film, determines
  the exposure necessary to create an image.
• Lens diaphragm (F/8, F/5.6 etc..)
• Shutter curtain (1/125, 1/250, 1/500 etc.)
• Film (100, 200 ISO etc..)
• Light, the quality and quantity of light control
  exposure.

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The Camera

• The Camera is a Electro-Mechanical device that
  allows us to make an image that preserves what
  our eyes see of a given seen. With use of a box
  (the camera), a hole (aperture) a means of
  focusing (lens), and film, we are able to
  preserve on film what we see at a given moment,
  but that which our mind forgets.

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The Camera

• Small Format Camera or 35 mm camera
• versatility/portability
• film selection
• lens selection
• accessories

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The Camera

• Medium Format or 120mm Camera
• Slightly larger in size than 35mm
• Larger Negative
• Fewer lenses
• Fewer functions
• Fewer films to select from

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The Camera

• Large Format Camera or 4x5 8x10 inch Cameras
• Very cumbersome
• Is not user friendly
• Fewer accessories
• Smaller film selection than even medium format

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The Camera

• Digital Cameras
• Instant images
• portability
• Cost! The cost can be extremely high for equal
  quality images
• Integrity issues

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The Camera

• Polaroid
• Instant images
• Lacks negative
• Quality of images
• Cost

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The Lens

• A lens is a device that uses convex glass or
  mirrors, enabling us to focus on the subject at
  hand.

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Lenses

• Refractive Lenses
• Catadioptric

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Lens Types

• Short (wide angle)
• Normal
• Telephoto
• Zoom
• Special Purpose

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Fixed Focal Lens
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Zoom Lenses
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Slow/Fast Lenses

• Lenses with f/stops such as f/1.4 though f/2.8
  are considered fast lenses. Fast lenses are
  called such because they have greater light
  gathering capabilities.
• Lenses with f/stops above F/4.0 are considered
  slow lenses. Slow lenses do not always have
  ideal light gathering capabilities, especially in
  low light situations.

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Digital Photography Terms

• PPI pixels per inch
• Digital cameras
• DPI dots per inch
• Scanners laser printers
• LPI lines per inch
• Screen pattern for printing newspapers
  magazines
• 1 pixel 8 DPI

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Altering Images

• Enhancement Make image better or greater in
  value desirability or attractiveness
• Lighten/darken a picture to see image better
• Manipulation Change by artful means so as to
  serve ones own purpose
• Change a color or take out a person in a picture

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Digital Photography/Imaging

• Digital Cameras rated in Pixels
• Companies round (e.g. a 2.0 megapixel camera may
  only be 1.6 megapixels)
• Printers best quality is only 300 dpi
• Media to record images
• Compact flash cards, smart media, memory sticks,
  etc.

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Types of files

• TIFF Compresses files w/o losing as much
  information (21 compression)
• JPEG most common used keep most information
  in a reasonable size file (301 compression)
• RAW must have specific software to use
• PSD Photoshop proprietary format must use
  Adobe Photoshop software

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Archiving Images

• Save image on CD-R or WORM
• This will be the negative Cant overwrite or
  alter image
• Best media to store images
• External Drive not as good, but adequate
• Software must be available to anyone buy of
  the shelf not software just for law
  enforcement
• Constantly update to new technology

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Advantages to using Digital

• Replaces the Polaroid cameras
• No film to load (media cards)
• See image instantly
• Can be used as a backup to film
• Some cameras are as good as ISO 400 film

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Disadvantages to Digital

• Cannot replace film
• Not good for enlargements, esp. court displays
• Must have a high quality printer ()
• Camera must be a minimum of 2.0 mega pixels
• High cost of all equipment

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Summary

• Hybrid system best Use 35mm, digital, and
  scanners / film scanner
• Use digital camera as backup / document scene
• Still use 35mm (scene evidence)
• Camera must be 2.0 megapixels or higher better if
  over 6.0 megapixels
• Negative is the first image made (save)