1 Digital Cameras Consumer digital cameras have been

1 Digital Cameras • Consumer digital cameras have been around since 1995 • What features make a good camera? • How do we optimize good features with a limited budget?

1 Exposure • How many photons contribute to each pixel? – More is better! • Exposure is a combination of several factors – – – Aperature Size Shutter speed Lens size Sensor Sensitivity Sensor size (bigger is generally better)

1 Lens • The lens gathers light • The lens focuses the image • Sharpess of the image depends on the lens • Larger lenses gather more light • Smaller lenses allow for a smaller camera

1 Lens Focal Length • Focal length – Macro • have short focal lengths • Allow imaging small objects – Normal • have intermediate focal lengths • Most cameras have one – Telephoto • have large focal lengths • Allow imaging far away objects

1 Field of View

1 Vignetting • A gradual fading of the image away from the center • Caused by lens optics

1 Optical Zoom • Changes lens focal length • More lenses can lead to glare and loss of sharpness • Large zoom can benefit from image stabilization

1 Digital Zoom • Digital zoom extracts a region • Similar to cropping • Use optical zoom if possible

1 Shutter Speed • Controls how long the sensor is exposed • Short – Need lots of light – Good for moving objects • Long – Good for stationary objects – Need less light

1 Aperture • Controls amount of light entering camera • Provides field of view – Small aperture • acts like a pinhole • Entire image in focus – Large aperture • Narrow range in focus • Provides emphasis on foreground objects

1 Viewfinder • Allows us to identify the content of the image • Optical – Through the lens – Off axis • Electronic – Small – Full-size

1 Camera Display • • Small Screen Review of images Camera control Viewfinder

1 Sensor • Acquires the image • Electronic equivalent of film • CCD – Charge-coupled device • CMOS – Complementary Metal Oxide Semiconductor http: //www. shortcourses. com/how/sensors/ccdwaffer. jpg

1 CCD vs. CMOS

1 Mosaic vs. Foveon

1 Analog to Digital Conversion • Electronic cameras convert energy from an analog signal to digital – Discrete in time – Discrete in amplitude

1 Quantum Noise • Based on the number of photons • Variation is the square root of the number of photons http: //telin. rug. ac. be/~frooms/research/steer/www/

1 Other Noise • Electronic – Heat – Cheap Electronics – Design • Senosor – Bad pixels • Hot • Cold – Bad line http: //www. starizona. com/ccd/software/biasframe. jpg • See http: //www. imatest. com/docs/tour_lightfall. html

1 Camera Speed • Time to read sensor • Time to write image to media • Faster is better

1 Compression • JPEG 2 • Is the image always compressed?

1 Data Storage Media • Physical device where images are stored • Tradeoffs – – – Physical size (smaller is better) Speed (faster is better) Data size (larger is better) Cost per GB (more is better) Reliability • How permanent is the storage? • What is the failure rate? – Availability • What other devices can use the media?

1 Noise • Statisitcal variations in the pixel values • Noise obscures detail

1 Battery Power • Provides camera with power • Disposable – Costly in long run – Low power • Rechargeable – Lithium – Ni. MH • Important question – How many pictures can be taken on one charge?

1 Camera Settings • What special features does the camera provide? – – – Shutter priority Aperture priority Movies Red-eye reduction Delayed shutter

1 Connectivity • How does the camera interface with computers? – – USB Firewire Serial Removable media

1 Flash • Does camera use a flash? – Internal – External

1 Tripod • Holds camera • Useful for – long exposures – Repeated shots

1 Carrying Case • Holds camera and other supplies – – – Tripod Batteries Recharger Manual Extra media

1 Hybrid Cameras • Digital camera that can directly print to polaroid film any desired photos • Preview of film images before processing • Dual film/digital camera where one can easily switch between the two modes • A 35 mm cassette that has the same form factor as a film camera, yet acquires digital images • Direct digital conversion of film during processing