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/11 f/8 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 1/8 1/15 1/30 1/60 1/125 1/250 1/500 1/1000 1/2000 Aperture Setting f/22 f/16 f/11 f/8 f/5.6

f/4 f/2.8

f/2 f/1.4

Depth of Field Large Shallow