Digital SingleLens Reflex Camera

1
Digital Single-Lens Reflex Camera

• Peter Hsieh
• Writing 2E

2
Introduction

• Digital Single-lens Reflex Camera, or DSLR, is a
  type of digital camera that provides the
  capability of interchanging lenses and wider
  photo-shooting options than normal consumer
  cameras.
• It serves the purpose of capturing images in
  digital format
• A DSLR contains a photographic lens, a
  viewfinder, a shutter, and an image sensor.

3
Design of a DSLR
When DSLR is not Capturing Image

• The photographic lens located in front of the
  camera directs lights into the camera body. Light
  is then reflected by the mirror to the pentaprism
  and finally travels to the viewfinder where
  photographers can observe the scene. Notice that
  the mirror is flipped down and the shutter covers
  the image sensor from recording lights.

Diagram originally from www.yesmag.bc.ca,
modified by Peter Hsieh
4
Design of a DSLR
When Capturing an Image

• The image capturing process starts when the
  shutter release button is pressed. Notice the
  mirror is flipped up from its original position,
  allowing light to travel to the sensor area. The
  shutter that covers the image sensor is now fully
  opened, and the image sensor is exposed under
  light and will be capturing the image.

Diagram originally from www.yesmag.bc.ca,
modified by Peter Hsieh
5
Specific Part
The Image Sensor The Introduction

• Image Sensor is the key device in DSLR, and
  serves the same function of capturing images as
  traditional films
• Image sensor is basically a silicon chip
  containing millions of light sensitive element
  called photosite, and is covered by a layer of
  color filter

Howstuffwork How Digital Camera Work
http//electronics.howstuffworks.com/digital-camer
a2.htm
6
Specific Part
The Image Sensor The Bayer Layer

• Bayer Layer is a common type of color filter used
  in a DSLR.
• It refers to a specific arrangement for the red,
  blue, and green color filters.
• Bayer Layer contains twice as many green filters
  as blue and red to best simulate the human sight.
  It is because human eyes are most sensitive to
  green lights.
• Once the incoming light hits the Bayer Layer,
  each single color filter on the layer will allow
  one specific color to pass through to the image
  sensor.

The upper layer is the Bayer layer. The lower
layer is the image sensor.
http//en.wikipedia.org/wiki/Bayer_filter
7
Specific Part
The Image Sensor The image capturing process

• Once the light passes through the Bayer layer,
  the photosites located beneath will start
  recording the brightness of the light by
  accumulating a charge. The charge goes higher
  when the image sensor is exposed longer under
  lights. Each charge will become a single pixel
  after processing, and all pixels will finally
  form a digital image and be stored in the memory
  card for future reconstruction and editing.

http//en.wikipedia.org/wiki/Bayer_filter
8
Specific Part
The Image Sensor The size

• There are two common sizes of image sensor used
  by DSLR.
• 135 size image sensor has a dimension of 36mm
  24mm and is also called the full-frame sensor.
• APS-C size image sensor has a dimension of 22mm
  15mm.
• The size of an image sensor has no effect on the
  size of the captured image, but affects the size
  of scene that will be captured.

This diagram illustrates the different sizes of
scene that a full frame and an APS-C sensor are
able to capture. The gray circle indicates the
total view, or the field of view, of the camera.
http//en.wikipedia.org/wiki/Bayer_filter
9
Specific Part
The Image Sensor The size

• The image displayed on the left illustrates a
  real example of the different fields of view that
  a full frame size sensor and an APS-C size sensor
  are able to capture.
• The image inside the box is equivalent to the
  scene captured by an APS-C sensor
• The overall image is equivalent to the scene
  captured by a full frame size sensor.
• Full frame size sensor has the advantage in
  wide-angle shooting. It is able to capture wider
  scene, and is often used for landscape
  photography.
• APS-C sensors capture narrower view, so objects
  in the image appear to be larger. It gives APS-C
  an advantage in long-distance shooting such as
  bird portraits because it is easier to emphasize
  on the photographed subject.

http//en.wikipedia.org/wiki/Bayer_filter
10
Specific Part
The Image Sensor The Pixel/Photosite Relations

• Every digital photograph is a combination of
  millions of pixel. Each pixel is produced by a
  single photosite on the image sensor so that each
  photograph will have a number of pixels
  equivalent to the number of photosites. DSLR is
  sometimes categorized by the number of million
  pixels. The number is referred to the number of
  photosite contained by the image sensor.
• The Canon 20D DSLR camera is categorized as an
  8.2 million pixel digital camera because its
  image sensor contains exactly of 8.2 million
  photosites. This specific camera is able to
  capture digital photographs with a maximum of 8.2
  million pixels. In general, a digital camera with
  more pixels is able to capture more details while
  provides sharper images.

Curtin, P. Dennis (2006). Image SensorCapturing
the Photograph. ensors/sensors.htm
11
Work Cited

• Curtin, P. Dennis (2006). Image SensorCapturing
  the Photograph. Retrieved March 7th, 2006, from
  tm
• Halley, Hd (2005). What is the Crop Factor The
  Expense of Digital Image Sensors. Retrieved March
  5th, 2006, from .html
• Wilson, Tracy, Nice, K., Gurevich G. (n.d.).
  Howstuffwork How Digital Camera Work. Retrieved
  March 5th, 2006, from works.com/digital-camera2.htm
• Wikipedia.org Bayer Filter, (2006) Retrieved
  March 6, 2006, from Bayer_filter