Camera Basics

How cameras workFilm vs DigitalTaking 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 camerasBUT, lenses refract light onto computer

chips rather than filmContains a logic board with

microprocessors and transistors.Microcontroller unit (MCU) – main chipImage sensor – converts light refracted

by lens element into a series of electrical charges

Parts of the camera

DiaphragmOpens and closes to control the amount of

light entering the cameraDiameter of the diaphragm is the aperture

ShutterControls how long the film is exposed to

lightDigital – shields the image sensor from

constant exposure

Making Images

Film responds chemicallyActive ingredient – gelatinous emulsion

filled with light-sensitive crystalsCrystals contain traces of silverWhen light hits the film impurities in the

crystals attract the silver atoms into clumpsStronger light = larger clumpsDevelopment process enlarges the clumps

making them visible

Image Sensor

Image sensor responds electronicallySensor is composed of a layer of silicon

covered with a grid of square electrodesSilicon has negatively charged particles –

electronsWhen light passes through the electrodes -

the electrons scatterVoltage applied to the electrodes attracts

the free electrons into clusters - photosites

Image Information

Images are stored as a collection of tiny squaresPixels = 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

JPEGJoint Photographic Experts GroupCompresses image dataSmaller picture filesUtilizes a lossy compression scheme

Some image data is sacrificed during the compression process

Common WWW format

Image size and Compression

TIFFTagged Image File FormatUncompressed image information

Can utilize LZW compressionLossless compression schemeOnly redundant image data is dumped

Larger file sizesUsed when quality is importantPrint and publishing format

Example

UncompressedSheep, sheep, sheep, sheep, sheep

Lossless compressionSeven sheep

JPEGsheep

Exposure

ISO – International Standards Organization ratingsThe image sensors’ sensitivityComparable to film ratingLower ISO – more light necessary for

pictureOrdinary 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 exposureClosed shutter means no light

Numbers indicate fractions of a secondEach 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

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