Digital Cameras

1
Digital Cameras

• Basic Info on Operations

2
How do digital cameras work?

• Digital Cameras convert analog information
  (represented by a fluctuating wave) into digital
  information (represented by ones and zeros, or
  bits).
• CDs, DVDs, HDTV, MP3s and DVRs are all built
  around the same basic process

3
Whats the difference b/w a digital camera and a
regular film camera?

• Film cameras depend on chemical and mechanical
  processes
• Film cameras do not even need electricity
• Digital Cameras have a built in computer which
  record images electronically

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What happens when a Digital Cameras takes a
picture?

• Once a pic is taken the image /pic must be
  converted into a form the computer
  recognizesbits and bytes
• A digital pic is just a long string of pixels 1s
  and 0s
• All of these pixels make up the image

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To help the process along

• A Digital Cameras has different lenses that help
  focus the light to create the image of a scene
• A 35 mm camera would focus the light onto a
  piece of film.a Digital Cameras focus the light
  onto a semi-conductor device that records the
  light electronically
• A computer breaks this info down into digital data

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What breaks down the info into digital data?

• A sensor converts the light into electrical
  charges
• Digital Cameras use CCDs (Charged Couple Devices)
  or CMOS (Complementary Metal Oxide Semiconductor)
• Both convert light into electrons
• Value is read of each cell in the image
• Both operate similarly converting the light into
  readable form

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Whats the real difference

• Because each pixel on a CMOS sensor has several
  transistors located next to it, the light
  sensitivity of a CMOS chip is lower. Many of the
  photons hit the transistors instead of the
  photodiode.
• CMOS sensors traditionally consume little power.
  CCDs, on the other hand, use a process that
  consumes lots of power. CCDs consume as much as
  100 times more power than an equivalent CMOS
  sensor.

• CCD sensors create high-quality, low-noise
  images. CMOS sensors are generally more
  susceptible to noise.
• CCD sensors have been mass produced for a longer
  period of time, so they are more mature. They
  tend to have higher quality pixels, and more of
  them.

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Confused?

• Although numerous differences exist between the
  two sensors, they both play the same role in the
  camera -- they turn light into electricity.
• To understand how a digital camera works, you can
  think of them as nearly identical devices.

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What else is important in a Digital Cameras?

• Resolution
• The amount of detail that the camera can capture
  and it is measured in pixels.
• The more pixels a camera has, the more detail it
  can capture and the larger pictures can be
  without becoming blurry or "grainy."

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Common Resolutions

• 256x256 - Found on very cheap cameras, this
  resolution is so low that the picture quality is
  almost always unacceptable. This is 65,000 total
  pixels.
• 640x480 - This is the low end on most "real"
  cameras. This resolution is ideal for e-mailing
  pictures or posting pictures on a Web site.
• 1216x912 - This is a "megapixel" image size --
  1,109,000 total pixels -- good for printing
  pictures.
• 1600x1200 - With almost 2 million total pixels,
  this is "high resolution." You can print a 4x5
  inch print taken at this resolution with the same
  quality that you would get from a photo lab.
• 2240x1680 - Found on 4 megapixel cameras -- the
  current standard -- this allows even larger
  printed photos, with good quality for prints up
  to 16x20 inches.
• 4064x2704 - A top-of-the-line digital camera with
  11.1 megapixels takes pictures at this
  resolution. At this setting, you can create
  13.5x9 inch prints with no loss of picture
  quality.

11
How do Digital Camerascapture color?

• Photosets are blind
• Photosites only keep track of the total intensity
  of light that strikes the surface
• To get full color of an image, most sensors use
  filtering to look at the light in its three
  primary colors
• All three colors get recorded and combined to
  create the full spectrum

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Capturing Color

• Beam splitter directs light to different
  sensors and each sensor only responds to one of
  the primary colors
• Rotate all three colors (red, green , blue) get
  rotated in front of a single sensor 3 separate
  images get recorded
• Color filter array most economical and
  practical method used to permanently place a
  filter over each photosite.
• Sensor gets broken up into r,g, b pixels
• Bayer filter pattern
• Most common and alternates a row of red and green
  filters with a row of blue and green filters.
• pixels are not evenly divided (as many green as
  there are blue and red combined)
• Why?
• Human eye is not a sensitive to all three colors
• Necessary to include all of green so as to create
  an image that they eye will perceive a true color

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Exposure Focus

• digital camera has to control the amount of light
  that reaches the sensor.
• The two components it uses to do this, the
  aperture and shutter speed, and are also present
  on conventional cameras.

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Exposure Focus

• Aperture The size of the opening in the camera.
  The aperture is automatic in most digital
  cameras, but some allow manual adjustment to give
  professionals and hobbyists more control over the
  final image.
• Shutter speed The amount of time that light can
  pass through the aperture. Unlike film, the light
  sensor in a digital camera can be reset
  electronically, so digital cameras have a digital
  shutter rather than a mechanical shutter

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Exposure Focus

• Aperture and shutter speed work together to
  capture the right amount of light needed to make
  a good image
• The camera also adjusts the lenses to control how
  the light is focused on the sensor.
• Most Digital Cameras use auto focus lenses

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Focal Length

• This is the biggest difference between a digital
  camera and a regular conventional camera
• So what is focal length
• The distance between the lens and the surface of
  the sensor
• This determines the magnification (zoom)
• Increasing the focal length increases the zoom /
  magnification and vice versa

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Digital Camera Lenses

• Fixed-focus, fixed-zoom lenses - These are the
  kinds of lenses on disposable and inexpensive
  film cameras -- inexpensive and great for
  snapshots, but fairly limited.

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Digital Camera Lenses

• Optical-zoom lenses with automatic focus -
  Similar to the lens on a video camcorder, these
  have "wide" and "telephoto" options and automatic
  focus. The camera may or may not support manual
  focus. These actually change the focal length of
  the lens rather than just magnifying the
  information that hits the sensor.

19
Digital Camera Lenses

• Digital-zoom lenses - With digital zoom, the
  camera takes pixels from the center of the image
  sensor and interpolates them to make a full-sized
  image. Depending on the resolution of the image
  and the sensor, this approach may create a grainy
  or fuzzy image. You can manually do the same
  thing with image processing software -- simply
  snap a picture, cut out the center and magnify
  it.

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Digital Camera Lenses

• Replaceable lens systems - These are similar to
  the replaceable lenses on a 35mm camera. Some
  digital cameras can use 35mm camera lenses.

21
Storage

• Early generations of digital cameras had fixed
  storage inside the camera.
• You needed to connect the camera directly to a
  computer with cables to transfer the images.

22
Storage

• Today's cameras are capable of connecting through
  serial, parallel, SCSI, USB or FireWire
  connections
• They usually also use some sort of removable
  storage device.

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Storage

• Digital cameras use various storage systems.
• These are like reusable, digital film, and they
  use a caddy or card reader to transfer the data
  to a computer.
• Many involve fixed or removable flash memory.
• Digital camera manufacturers often develop their
  own proprietary flash memory devices, including
  SmartMedia cards, CompactFlash cards and Memory
  Sticks.

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Storage

• Removable storage devices include
• Floppy disks
• Hard disks, or microdrives
• Writeable CDs and DVDs