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Digital Photography DeCal. EECS98 Nathan Yan. How it works. All cameras, film or digital, work the same: Photons are projected onto a photo-sensitive plane which records the light information. How it works. - PowerPoint PPT Presentation
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Digital Photography DeCal
EECS98Nathan Yan
All cameras, film or digital, work the same:Photons are projected onto a photo-sensitive plane which records the light information
How it works
How it worksBy confining light to only photons which pass through a certain point, we begin to resolve “detail”
Image process
or
History of Camera Development• Many pinhole-type cameras dating back to the 11th century• Joseph Niépce recorded the first photograph in 1826, using a
photo-sensitive silver/chalk mixture (8 hour exposure)• Development of recording mediums more responsive to light:
wet plates, dry plates• George Eastman introduces photographic film in 1885, and
debuts the “Kodak” camera in 1888 – a cheap and easy to operate camera that began to popularize cameras
• Oskar Barnack developed the Leica camera in 1925, which popularized 35mm film standard
• Ihagee introduced the first single-lens reflex camera, Exakta, in 1933, allowing photographers to view image “through the lens”
• Auto-focus developed in the Konica C35AF in 1977
History of Digital Camera Development• Began with charged couple device (CCD) cameras that recorded to analog
media• Steve Sasson produced the first for Kodak in 1973
• Solid state CCD that recorded output onto cassette tape• Resolution: 10,000 pixels, or 0.01 megapixels
• First practical use in 1984, for journalism• Canon RC-701 recorded images onto “video floppies”• During 1984 Olympics images could be transmitted via telephone lines, and
image quality (780x585, .4MP) was acceptable for newsprint• JPEG image compression standard introduced in 1988• First true digital camera: Fuji DS-1P debuted in 1988, recording a computerized
image file to onboard memory• First camera with live image feed to LCD: Casio QV-10 in 1995• First “professional” digital SLR camera natively designed: 2.74MP Nikon D1 in
1999• First affordable “consumer” digital SLR: 6MP Canon Digital Rebel 300D in 2003
- $1000
Input:Light «photons»
Output:Electrical
signals
The Imaging Sensor
Si
Si
Si
Si
Si
Photowell
Bucketloads of Electrons!
Many electronsVoltage: HighImplication: Many photons detected, bright exposureResult: bright image
Few electronsVoltage: LowImplication: Few photons detected, dark exposureResult: dark image
Max electronsVoltage: MaxImplication: Max photons detected, brightest exposureResult: White image
No electronsVoltage: ZeroImplication: No photons detected, darkest exposureResult: Black image
Bigger aperture = more light!
Aperture
Longer shutter speed (exposure time) = more light collected!
Shutter speed
Electrical signal
Accumulated charge
Amplifier Voltage
Measurement
Amplified electrical signal
ISO is a “sensitivity” – higher ISO means more signal (brightness) for the input (light) you actually get
ISO sensitivity
x010
x010
x100
x111
x111
x111
x111
x111
x000
x000
x100
x110
x100
x111
x111
x111
Use software to multiply the pixel values
2x4x8x16x
Digital Multiplication
Si
Si
Si
1010
1010
0100
Image process
or
PhotonsPhotoelectrons
Electrical signal
Accumulated charge
Dig
ital r
epre
sent
atio
n of
ele
ctric
al s
igna
l
Image file
Amplifier
Analog-to-Digital
Converter
Amplified electrical signal
Photons
Electrons
Voltage Reading
Voltage Signal
Image Brightness
Shutter speed
Aperture
Quantum efficiency
Signal Amplificatio
n
Digital Multiplicatio
n
Exposure “Stops”
Stops Exposure
Shutter speed Aperture ISO sensitivity
-4 1/16x 1/1600s f/22 ISO50-3 1/8x 1/800s f/16 ISO100-2 1/4x 1/400s f/11 ISO200-1 1/2x 1/200s f/8.0 ISO4000 1x 1/100s f/5.6 ISO800+1 2x 1/50s f/4.0 ISO1600+2 4x 1/25s f/2.8 ISO3200+3 8x 1/12s f/2.0 ISO6400+4 16x 1/6s f/1.4 ISO12800