Camera Basics

1
Camera Basics

• How cameras work
• Film vs Digital
• Taking control

2
Film Camera

• Viewfinder Cameras
• Image viewed through a simple lens providing an
  image of how the final picture will look.
• Light travels from the subject through the lens
  to the film
• Parallax error

3
Film Camera

• Single Lens Reflex (SLR)
• Photographer looks directly through the lens to
  see the picture.
• Light from the lens reflects off an internal
  mirror up to the viewing system.
• Mirror swings out of the way to allow light to
  expose the film.
• Includes a prism to invert the reversed image

4
Digital Camera

• Lenses work just like film cameras
• BUT, lenses refract light onto computer chips
  rather than film
• Contains a logic board with microprocessors and
  transistors.
• Microcontroller unit (MCU) main chip
• Image sensor converts light refracted by lens
  element into a series of electrical charges

5
Parts of the camera

• Diaphragm
• Opens and closes to control the amount of light
  entering the camera
• Diameter of the diaphragm is the aperture
• Shutter
• Controls how long the film is exposed to light
• Digital shields the image sensor from constant
  exposure

6
Making Images

• Film responds chemically
• Active ingredient gelatinous emulsion filled
  with light-sensitive crystals
• Crystals contain traces of silver
• When light hits the film impurities in the
  crystals attract the silver atoms into clumps
• Stronger light larger clumps
• Development process enlarges the clumps making
  them visible

7
Image Sensor

• Image sensor responds electronically
• Sensor is composed of a layer of silicon covered
  with a grid of square electrodes
• Silicon has negatively charged particles
  electrons
• When light passes through the electrodes - the
  electrons scatter
• Voltage applied to the electrodes attracts the
  free electrons into clusters - photosites

8
Image Information

• Images are stored as a collection of tiny squares
• Pixels picture elements
• Resolution number of pixels captured by the
  image sensor.
• Masking pixels clipped away around the perimeter
  of the image
• Interpolation invention of extra pixels

9
Image size and Compression

• JPEG
• Joint Photographic Experts Group
• Compresses image data
• Smaller picture files
• Utilizes a lossy compression scheme
• Some image data is sacrificed during the
  compression process
• Common WWW format

10
Image size and Compression

• TIFF
• Tagged Image File Format
• Uncompressed image information
• Can utilize LZW compression
• Lossless compression scheme
• Only redundant image data is dumped
• Larger file sizes
• Used when quality is important
• Print and publishing format

11
Example

• Uncompressed
• Sheep, sheep, sheep, sheep, sheep
• Lossless compression
• Seven sheep
• JPEG
• sheep

12
Exposure

• ISO International Standards Organization
  ratings
• The image sensors sensitivity
• Comparable to film rating
• Lower ISO more light necessary for picture
• Ordinary film 200 - 400

13
Exposure

• Aperture
• Opening of the diaphragm to let in light
• F-stops
• Each stop represents a factor of 2 in the amount
  of light permitted.
• Affects the depth of field
• How much in front of or behind the object will be
  in focus.
• The smaller the aperture, the greater the depth
  of field, the more of the photograph is in focus.

14
Aperture
f/22
f/8
f/2.8
f/2
f/5.6
f/11
15
Shutter Speed

• Shutter speed controls the length of the exposure
• Closed shutter means no light
• Numbers indicate fractions of a second
• Each is either half or double the length of time
  of the one next to it.
• Parallel to the aperture

16
Equivalent Exposure Settings
Appearance of subject Shutter Speed Aperture Setting Depth of Field
Blurred, fuzzy 1/8 f/22 Large
1/15 f/16
1/30 f/11
1/60 f/8
1/125 f/5.6
1/250 f/4
1/500 f/2.8
1/1000 f/2
Sharp, clear 1/2000 f/1.4 Shallow