Image Capture Media

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• Image Capture Media

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• Describe the differences between digital image
  capture and the traditional chemical method of
  image capture.
• Explain the operation of a sensor in capturing an
  image.
• Distinguish between the physical structures of
  black-and-white film and color film.
• Explain the method by which a latent image is
  formed.

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• Describe the film speed rating system as a
  measure of sensitivity to light.
• List the various types and forms of film.
• List the advantages and disadvantages of color
  negative and color positive films.
• Demonstrate the film loading procedures for
  common types of cameras.

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Digital vs. Film Image Capture

• Electronic arrays capture images on photo sites
• Digital sensor captures image
• Camera processes image
• File stored on removable device
• Film records a latent image
• Made permanent by chemical processing

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Digital vs. Film Image Capture (Cont.)

• Photography long considered an image-capture
  process requiring chemicals and light
• Digital photography far more popular than film
• Pixels arranged to form area array
• Digital images stores as files

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Film Capture and Processing
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Digital Imaging Process

• Light strikes pixel
• Generates electrical charge
• Charge strength varies with brightness
• Electrical charge converted to analog signal
• Analog signal converted to digital signal
  processed by cameras firmware
• CCD and CMOS devices process signals differently

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Digital Imaging Process (Cont.)
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Digital Cameras See Only Gray

• Bit depth determines gray levels
• 1-bit pixel 2 shades (black or white)
• 8-bit pixel 256 shades
• Color information records filtered light to
  obtain grayscale channels

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Bayer Pattern

• Filter decals on pixels
• Twice as many green filters

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Sensor Sizes

• Full-frame print (24 mm ? 36 mm)
• Same as 35 mm film
• Most professional cameras
• APS-size (17 mm ? 30 mm)
• Compact and prosumer cameras

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Pixel Sizes

• Full-frame pixels 1/3 larger than APS
• More light-sensitive
• Existing pixel values averaged to create new
  pixels through interpolation

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Scanning Backs and Studio Cameras

• Linear arrays used exclusively
• Trilinear arrays preferred to area arrays
• Long exposures generate heat which can cause
  digital noise and blooming

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Digital Image Storage

• Memory card flexible removable memory device

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Digital File Formats

• Files may be compressed to use less storage space
• RAW
• TIFF (.tif)
• JPEG (.jpg)

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Removable Storage Devices

• Secure Digital (SD)
• CompactFlash (CF)
• Capacities from 128 Mb64 gigabytes (GB)
• Memory Stick?
• xD-Picture
• Microdrive
• SmartMedia

Lexar/SanDisk/Fujifilm/Sony Corporation/Hitachi
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Storage Capacities

• Depends on sensor size and file type

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Card Speed

• Transfer rate from camera to card
• Useful for sports and action photography
• Cameras also possess a buffer, or internal memory

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Film Image Capture

• Evolution of film
• Daguerrotype/tintype
• Wet (collodion) glass plates
• Dry (silver bromide) glass plates
• Roll film

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Physical Structure of Film

• Flexible base material
• Light-sensitive (emulsion) layer(s)
• Special-purpose layers

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Black-and-White Film

• Film base
• Single emulsion layer
• Three additional layers
• Supercoat
• Subbing layer
• Antihalation layer
• Surfactant used as wetting agent

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Color Film

• Film base
• Three emulsion layers
• Five additional layers

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How Light Affects Film

• Photons affect silver halides
• Silver bromide ions
• Silver bromide crystals contain sensitivity
  specks
• Silver clumps form latent image
• Negative density proportional to light
• Positive (print) will reverse values

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Characteristic Curve

• Relates exposure to density
• Different for each film
• First section film base plus fog
• Middle-density section straight-line section
• Right end shoulder

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Characteristic Curve (Cont.)
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Film Speed Ratings

• Measurement of light-sensitivity
• Lower number less sensitive
• Higher number more sensitive
• Sensitivity doubles/halves with each ISO step
• Film grain increases with speed
• Based on requirements by International Standards
  Organization (ISO)

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Film Speed/Grain Relationship

• Grain increases along with film speed
• Film emulsion improvements reduce grains at high
  speeds
• Tabular grains
• Chromogenic film produces a grainless
  black-and-white image

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Reversal Film

• Transparency is first generation image
• Exposure more critical than print film
• Two-step development process
• Negative silver image
• Color dyes (positive) replace silver

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Negative/Positive Film

• Most common film type
• Monochrome and color
• Wide range of speeds
• Processing readily available
• Developed film is negative
• Print is positive (second generation) image
• High-contrast lithographic film

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Instant-Print Film

• Film developer
• Print in 60 seconds or less
• Monochrome and color
• Mostly replaced by digital imaging

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Forms of Film

• Cartridge film
• Almost obsolete
• Film in cassettes
• 35 mm and APS
• Drop-in loading
• Lighttight cassette protects film
• Film loader required

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Forms of Film (Cont.)

• Roll film
• Medium-format cameras
• Paper backing holds/protects film
• Sheet film
• Individual, thicker film sheets
• Must be used in holders
• 4? ? 5? most common today

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• Where do the similarities between traditional and
  digital image capture end?
• When the light rays reflected from the subject
  reach the cameras image receiver.

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• Many digital camera sensors have red, blue, or
  green color filter decals applied over the
  individual pixels in an arrangement called a
  _____ pattern.
• A. Bartel
• B. Bayer
• C. Boxcar
• D. Bizet
• B. Bayer

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• Color film may have as many as nine layers,
  including _____ separate emulsion layers.
• three

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• True or False? Photons of light striking the film
  emulsion form a latent image.
• True

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• Film with an ISO rating of 400 is ____ times more
  sensitive to light than an ISO 100 film.
• four

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• Antihalation layer
• The bottommost layer of film, located on the back
  side of the base. This layer prevents light rays
  from being reflected back through the base and
  emulsion. Without this layer, reflected light
  could form halos (halation) around bright objects
  in the photograph.
• APS-size
• Sensor used in most digital cameras. The sensor
  is approximately 17 mm ? 30 mm in size, like the
  film used in Advanced Photo System cameras.
  (Full-frame sensors are 24 mm ? 36 mm,
  corresponding to the 35 mm film frame.)

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• Area array
• A grid made up of rows and columns of electronic
  sensors.
• Bit depth
• A numeric expression of the number of shades of
  gray a pixel is capable of displaying.
• Blooming
• In a digital photo, the smearing or bleeding of
  some color pixels, especially red, into adjacent
  parts of the image.

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• Buffer
• Internal memory in the camera that functions as a
  holding tank for image information already
  processed but not yet transferred to the memory
  card.
• Card speed
• A measure of how rapidly image files can be
  transferred from the camera to the memory card.
• Characteristic curve
• An S-shaped graph that serves as a snapshot of
  a given films reaction to light. It shows the
  relationship between exposure and density
  increase.

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• Chromogenic film
• A type of black-and-white film that produces an
  essentially grainless image composed of dyes,
  rather than silver.
• Collodion
• A basic emulsion ingredient of the wet-plate
  process, consisting of cellulose nitrate
  dissolved in ether or alcohol. A halogen salt
  such as potassium iodide also is dissolved in the
  mixture.

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• Color information
• Red, green, and blue values recorded by filtering
  the light striking the digital sensor to obtain
  three different grayscale channels.
• CompactFlash (CF)
• A small, solid-state memory card, available in a
  wide range of capacities, that is slipped into a
  slot on the camera.

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• Compressed file
• One that has been converted to a format that
  allows it to be saved in a smaller size to take
  up less storage space or to speed up transfer
  time.
• Digital noise
• Tiny light-colored spots especially noticeable in
  shadow areas of a scan or image capture.

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• Digital signal
• Image information that is encoded as a series of
  on/off states (usually represented by 1 or 0),
  rather than varying continuously (an analog
  signal).
• Drop-in loading
• A feature of Advanced Photo System cameras that
  allows the consumer to merely open a film door on
  the camera and insert the cassette. The film is
  then automatically loaded and advanced to the
  first frame.

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• Electronic array
• An arrangement of millions of tiny solid-state
  photo sites used to capture an image in a digital
  camera.
• File
• An individual digital image that can be stored,
  transferred, or manipulated.
• File formats
• Different modes of saving image data, such as
  JPEG or TIFF.

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• Film
• A light-sensitive, silver-based emulsion coated
  on a smooth, usually flexible plastic, base.
• Film base plus fog
• The minimal density of a clear film area, such as
  the strip between frames. The tiny amount of
  density is caused by the processing chemicals
  (rather than light). Also, a short, horizontal
  section at the left end of the characteristic
  curve.

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• Film loader
• A lighttight device that holds a roll of bulk
  film and allows a desired number of frames of
  film to be wound into a cassette.
• Film speed
• The films sensitivity to lightthe higher the
  film speed, the less light is needed to create a
  latent image on the emulsion.

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• Filter decals
• Transparent color overlays applied in a
  checkerboard pattern over individual sensors in a
  CCD or CMOS array. There are usually twice as
  many green filters as red or blue filters,
  because human vision is most sensitive to the
  light values contained in the green channel of a
  color image.
• Firmware
• The built-in program found in a digital camera or
  similar device.

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• Full-frame print
• A print made without cropping. A full-frame print
  from a 35 mm negative on an 8? ? 10? sheet would
  result in an image approximately 6 ½? ? 9 ½?.
• Gigabytes (GB)
• A quantity used to describe storage capacity of
  digital devices, such as computer memory or
  camera memory cards approximately equal to 1
  million bytes.
• Gray levels
• The distinct steps between pure white and pure
  black.

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• Image-capture process
• Using a camera to record a scene on film or a
  digital sensor.
• International Standards Organization (ISO)
• A body that publishes standard sets of
  requirements to ensure uniformity of such items
  as film speeds.
• Interpolation
• In scanning or image-editing applications, the
  creation of new image pixels by averaging the
  values of the surrounding existing pixels.

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• Ions
• Atoms carrying a positive or negative electrical
  charge.
• JPEG
• The most common compressed file format, developed
  by the Joint Photographic Experts Group. It can
  be used to reduce file size by a small or large
  amount.
• Latent image
• A photographic image that will not become visible
  until developing chemicals are used to bring it
  out and make it permanent.

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• Linear array
• Image-capture arrangement consisting of a long
  array containing only one to three rows of CCDs.
  Linear arrays are used in scanning-back cameras
  for studio work, and in flatbed scanners.
• Lithographic film
• A high-contrast material that produces an image
  without graduated tones. The film is either black
  or clear. Sometimes referred to as lith film.
• Memory card
• A digital storage device used in cameras
  available in a number of forms and a wide range
  of capacities.

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• Memory Stick?
• A form of memory card used primarily in Sony
  cameras.
• Microdrive
• A tiny hard drive the size of a CompactFlash
  memory card.
• RAW
• File containing the basic image information
  captured by the cameras sensor and saved with a
  minimal processing.

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• Scanning backs
• Studio capture devices that make use of a
  trilinear array, rather than an area array.
• Secure Digital (SD)
• Memory cards that are physically smaller and
  thinner than CompactFlash cards, and are
  available with capacities from 128Mb to 8Gb.
• Sensitivity specks
• Impurities believed to play the important role of
  focal points or sites for the formation of the
  silver clumps making up the latent (undeveloped)
  photographic image.

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• Shoulder
• The right end, or high-density portion, of the
  characteristic curve, representing the highlights
  of a scene.
• Silver halide salt
• A light-sensitive chemical compound used as a key
  ingredient of photographic emulsions.
• SmartMedia
• An early form of removable memory card for
  digital cameras.

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• Straight-line section
• The middle-density portion of the characteristic
  curve, where the density/exposure relationship is
  most nearly proportional.
• Subbing layer
• A very thin coating of pure gelatin that helps
  bond the emulsion to the base.

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• Supercoat
• The very thin, tough topmost layer of the film.
  Its primary purpose is to protect the emulsion
  from abrasion during exposure and processing.
• Surfactant
• An ingredient of the films supercoat that
  promotes absorption of processing chemicals to
  help ensure even development.
• Tabular grains
• A thinner flatter form of silver halide grains,
  developed to allow an increase in film speed
  without a corresponding increase in visible
  grain.

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• TIFF
• Tagged Image File Format.
• Trilinear array
• In a scanner or scanning back, a bar containing
  three rows of sensors that is moved across the
  image capture area. One row of sensors is
  filtered to capture red wavelengths one is
  filtered for green, and the third is filtered for
  blue.
• xD-Picture
• Tiny memory cards, about the size of a postage
  stamp, used in some digital cameras. They are
  available in capacities of 16Mb to 2Gb.