A digital camera sensor contains an array of light-sensitive photosite squares, each containing a photo diode that converts light photons into electrons. The electrons are stored in an electron well within the photosite. A processor then examines data from neighboring pixels to estimate the red, green, and blue color values for each pixel through a process called demosaicing. The sensor operates similarly to the human visual system by gathering light information and processing it to produce an image.

1. How a digital sensor works
The lens in a camera focuses light on
a plane behind the rear element

2. Typical Sensor Array in a Digital Camera
an array of light-sensitive spots, called photosites usually
square in shape and laid out in rows and columns

3. Sensor Architecture
Light-sensing portion of the photosite is called
photo diode.

4. ELECTRONS = the “wild children” of the atom family

5. Photo Diode
With some sensors the active light gathering area is as little as
25% of the total surface area of the chip. There is non-light
responsive space between adjacent photo diodes.

6. Light to photosite in sensor
photo diode in photosite converts
the light photons to electrons
Photosite stores electrons in the
electron well buried in the photosite

7. NOISE . . . Hot pixels and lost data

8. Light to photosite in sensor
photo diode in photosite converts the light photons to electrons
Photosite stores electrons in the electron well buried in the photosite
PROCESSING
Processor looks at blocks of this data and tries to guess the
actual RGB color value of each pixel by comparing
(demosaicing) it examines a block of adjacent pixels and uses
that data to build the missing two values for each location.
( interpolation in mathematics, software routine that does this
is more correctly called demosaicing.)

9. Sensors are designed to operate like the human brain

10. Light to photosite in sensor
photo diode in photosite converts the light photons to electrons
Photosite stores electrons in the electron well buried in the photosite
PROCESSING
“guess” the actual RGB color value of each
pixel demosaicing
JPEG PROCESSING
Compression = pixels destroyed or eliminated
by guessing actual color value

11. Depth of Field and Focal Length
DOF = depth of field
FOV = Field of View
Bokeh

12. How much
gear do
you really
need?

13. The longer the focal length, the creamier the bokeh
Focal Length: 600 mm (300mm lens with 2.0 teleconverter)
Iso 800
F/8 at 1/80

14. Narrow depth of field isolates the subject
Focal Length: 300mm
Iso 400
f/4 at 1/4000

15. Focal length: 280mm
Iso: 800
f/5.6 at 1/60

16. Focal Length: 60mm (macro)
Iso: 200
f/8 at 1/200

17. Focal length: 18mm
Iso: 100
f/6.3 at 1/100

18. Focal Length: 24mm
Iso: 100
f/1.4 at 1/800

19. Focal Length: 85mm
Iso 100
f/1.8 at 1/200

20. Focal Length: 85mm
Iso 1600
f/1.8 at 1/125

21. Focal Length: 10mm
Iso 100
f/5 at 1/200

22. The “Holy Trinity” or the exposure Triangle
ISO (sensitivity to light)
Good combination = good photo
Shutter Speed Aperture (f-stop)