Camera
Content
Analog
The real world is analog. Light and sound come in waves that our senses interpret.
Unfortunately it’s difficult to invent a technology that records an analog wave
Fortunately, storing a series of numbers is much simpler. You can carve them in stone,
write them on paper, or store them on a CD
When you record, them there’s no loss of data
Digitizing = the process of converting something into numbers
Film vs Digital
Film and digital cameras record an image by using a lens to focus light onto a focal
plane
The lens focuses the light through an aperture and a shutter onto a piece of film held on
the focal place
In a digital camera, instead of a piece of film, an image sensor sits on the focal plane. An
image sensor is a special type of silicon chip with light-sensitive capabilities
The most common kind of image sensor is called a CCD, a charge coupled device
When you take a picture, the image sensor samples the light coming through the lens
and converts that light into electrical signals
After the image sensor is exposed, these signals are boosted by an amplifier and sent to
an analog - to digital converter that turns the signals into digits
Once the camera’s on-board computer has calculated the final image, the new image
data is stored on a memory card
Day 2
From Black and White to Color
James Clerk Maxwell asked photographer Thomas Sutton to take three photographs of
the same piece of fabric
o He took three photographs with three different filters: red, blue and green. Then,
he projected them onto a screen with three different projectors covered in
corresponding filters, leading to the first color image … in 1869!
How are colors mixed
Red, green, and blue - the three additive primary colors - can be mixed to make other
colors. here the colors overlap creates new colors: cyan, magenta, and yellow. These
are the primary colors of ink
Photosites, Arrays, Interpolation and the Photoelectric Effect
Photographic film is covered with an emulsion of light-sensitive, silver-laden crystals.
When light hits the film the silver atoms clump together. The more light there is the
bigger the clumps
The photoelectric effect occurs when some metals release electrons when exposed to
light (founded by Einstein → got him that Noble Prize doh)
Photosites - the image sensor in your digital camera is a silicon chip that is covered with
a grid of small electrodes (one for each pixel)
Before you can shoot a picture, your camera charges the surface of the CCD with
electrons. Thanks to the photoelectric effect, when light strikes a particular photosite, the
metal in the site relates some of its electrons
Because each photosite is bounded by non-conducting metal, the electrons remain
trapped. Each photosite is like a little well, strong up more and more electrons as more
and more photons hit it
After exposing the CCD to light, your camera simply has to measure the voltage at each
site to determine how many electrons are there, and, thus, how much light hit that
particular site
The term “charge-coupled device” is derived from the way the camera reads the charges
of individual photosites
Interpolation - filling in the missing pixels (all digital cameras do it to make color images)
Each photosite on your camera’s image sensor is covered by a filter -- red, green, or
blue. This combination of filers is called a color filter array
A common pattern is the Bayer Pattern
Your digital camera will calculate the color of any given pixel by analysing something
They eye is most sensitive to green (for humans)
The real world is analog. Light and sound come in waves that our senses interpret.
Unfortunately it’s difficult to invent a technology that records an analog wave
Fortunately, storing a series of numbers is much simpler. You can carve them in stone,
write them on paper, or store them on a CD
When you record, them there’s no loss of data
Digitizing = the process of converting something into numbers
Film vs Digital
Film and digital cameras record an image by using a lens to focus light onto a focal
plane
The lens focuses the light through an aperture and a shutter onto a piece of film held on
the focal place
In a digital camera, instead of a piece of film, an image sensor sits on the focal plane. An
image sensor is a special type of silicon chip with light-sensitive capabilities
The most common kind of image sensor is called a CCD, a charge coupled device
When you take a picture, the image sensor samples the light coming through the lens
and converts that light into electrical signals
After the image sensor is exposed, these signals are boosted by an amplifier and sent to
an analog - to digital converter that turns the signals into digits
Once the camera’s on-board computer has calculated the final image, the new image
data is stored on a memory card
Day 2
From Black and White to Color
James Clerk Maxwell asked photographer Thomas Sutton to take three photographs of
the same piece of fabric
o He took three photographs with three different filters: red, blue and green. Then,
he projected them onto a screen with three different projectors covered in
corresponding filters, leading to the first color image … in 1869!
How are colors mixed
Red, green, and blue - the three additive primary colors - can be mixed to make other
colors. here the colors overlap creates new colors: cyan, magenta, and yellow. These
are the primary colors of ink
Photosites, Arrays, Interpolation and the Photoelectric Effect
Photographic film is covered with an emulsion of light-sensitive, silver-laden crystals.
When light hits the film the silver atoms clump together. The more light there is the
bigger the clumps
The photoelectric effect occurs when some metals release electrons when exposed to
light (founded by Einstein → got him that Noble Prize doh)
Photosites - the image sensor in your digital camera is a silicon chip that is covered with
a grid of small electrodes (one for each pixel)
Before you can shoot a picture, your camera charges the surface of the CCD with
electrons. Thanks to the photoelectric effect, when light strikes a particular photosite, the
metal in the site relates some of its electrons
Because each photosite is bounded by non-conducting metal, the electrons remain
trapped. Each photosite is like a little well, strong up more and more electrons as more
and more photons hit it
After exposing the CCD to light, your camera simply has to measure the voltage at each
site to determine how many electrons are there, and, thus, how much light hit that
particular site
The term “charge-coupled device” is derived from the way the camera reads the charges
of individual photosites
Interpolation - filling in the missing pixels (all digital cameras do it to make color images)
Each photosite on your camera’s image sensor is covered by a filter -- red, green, or
blue. This combination of filers is called a color filter array
A common pattern is the Bayer Pattern
Your digital camera will calculate the color of any given pixel by analysing something
They eye is most sensitive to green (for humans)
