Transcript Camera Basics - Texas A&M University

Camera Basics
How cameras work
Film vs Digital
Taking control
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
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
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
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
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
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
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
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
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
Example
Uncompressed
Sheep, sheep, sheep, sheep, sheep
Lossless compression
Seven sheep
JPEG
sheep
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
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.
Aperture
f/22
f/8
f/11
f/5.6
f/2.8
f/2
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
Equivalent Exposure Settings
Appearance of
subject
Blurred, fuzzy
Sharp, clear
Shutter Speed
Aperture
Setting
1/8
f/22
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
1/2000
f/1.4
Depth of Field
Large
Shallow