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

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 Shutter SpeedAperture Setting Depth of Field Blurred, fuzzy1/8f/22Large 1/15f/16 1/30f/11 1/60f/8 1/125f/5.6 1/250f/4 1/500f/2.8 1/1000f/2 Sharp, clear1/2000f/1.4Shallow