17. Camera Principles
Scene Image
Resulting image is
mirrored and inverted
Small aperture results in
very long exposures
Light Rays
Pinhole
Camera
18. Camera Principles
Scene Image
Increasing the pinhole
size provides more light to
shorten exposure times
but introduces distortion of
light rays resulting in poor
Light Rays
Pinhole image quality
Camera
19. Lens Principles
Scene Image
Simple lens refracts light
to reduce distortions
Light Rays
Simple Lens
20. Lens Principles
Scene Image
Compound lens
designed to control
variety of lens
aberrations which
Light Rays affect both image
Compound Lens sharpness and colour
21. Camera Elements
Lens
Shutter
Viewfinder system
Focusing mechanism
Transport
Light Meter
22. Basic Elements of a Camera
viewfinder
transport
shutter aperture
lens
light
sensitive
medium
focusing mechanism
23. Camera Types
Rangefinders
Single Lens Reflex (SLR)
Twin Lens Reflex (TLR)
Monorail
29. Exposure Control
Aperture value controls amount of light
Shutter speed controls duration exposure of time
Combination of aperture and shutter speed gives
correct exposure - for a particular light sensitivity
Combination defined as an exposure value (EV)
Standard light sensitivity is 100 ISO (ASA)
Higher light sensitivity provide faster exposure times
Lower light sensitivity provide slower exposure times
Fast film has a more grainy structure than slow film
30. Exposure Control: Aperture
Aperture controls amount of light via lens iris
Iris adjusted by changing aperture value on lens
Large f number = smaller iris size = less light
Small f number = larger iris size = more light
32. Exposure Control: Shutter
Shutter controls time light exposed to medium
Typical ranges 1 second - 1/2000th sec
Shorter (faster) shutter speeds = less time
Longer (slower) shutter speeds = more time
Shutter positioned at the focal plane or between the
lens (medium format)
Focal plane shutters can be horizontal run or vertical
run
34. Exposure Balance
f8 1 / 250th
f 11 100 ISO 1 / 250th
f8 200 ISO 1 / 500th
200 ISO
35. Exposure Balance: Three-Way
Exposure balanced between medium sensitivity
aperture value and shutter speed
Double or half the sensitivity = one ‘stop’
Double or half the shutter speed = one stop
Aperture values change by a factor of 1.4 = one stop
36. Exposure Modes
Manual - you set aperture and shutter speed based
on light reading
Aperture Priority - you set aperture and camera
calculates and sets the shutter speed based on light
reading
Shutter Priority - you set the shutter speed and
camera calculates and selects aperture based on
light reading
Fully Programmed - Camera selects both aperture
and shutter speed based on light reading
37. Lenses
Lenses interchangeable on SLR cameras
Lens bayonet - mounts to camera body
Each manufacture’s lens mount is unique
Lenses available from independent lens
manufactures and for several different lens mount
Lenses provided by independent manufactures are
generally less expensive than camera’s own brand
May not be as good optically or have same build
quality as cameras own brand lenses
42. Angle of View for 35mm
50mm provides
natural perspective
Shorter focal length lenses have angle of view which gives for the 35mm
format
steeper perspective
Longer focal length lenses have narrow angle of view which
gives flatter perspective
43. Advanced features
Autofocus
Image stabilisation
Intelligent recognition of faces and
scenes
46. Autofocus (3)
The microprocessor in the camera looks at the strip of pixels and looks
at the difference in intensity among the adjacent pixels. If the scene is
out of focus, adjacent pixels have very similar intensities. The
microprocessor moves the lens, looks at the CCD's pixels again and
sees if the difference in intensity between adjacent pixels improved or
got worse. The microprocessor then searches for the point where there
is maximum intensity difference between adjacent pixels -- that's
the point of best focus. Look at the difference in the pixels in the two
red boxes above: In the upper box, the difference in intensity between
adjacent pixels is very slight, while in the bottom box it is much
greater. That is what the microprocessor is looking for as it drives the
lens back and forth.
47. Autofocus (4)
Passive autofocus must have light and image contrast in order to do
its job. The image needs to have some detail in it that provides
contrast. If you try to take a picture of a blank wall or a large object of
uniform color, the camera cannot compare adjacent pixels so it cannot
focus.
There is no distance-to-subject limitation with passive autofocus like
there is with the infrared beam of an active autofocus system. Passive
autofocus also works fine through a window, since the system "sees"
the subject through the window just like you do.
(Courtesy How Stuff Works)
48. Image stabilisation
Canon’s newly developed Hybrid IS technology optimally compensates
for angular camera shake (rotational) and shift camera shake (linear).
Sudden changes in camera angle can cause significant blur in images
taken during standard shooting, whereas blur caused by shift-based
shaking, when a camera moves parallel to the subject, is more
pronounced in macro and other close-up photography.
49. IS: How is it done?
The new Hybrid IS technology incorporates an angular velocity sensor
that detects the extent of angular camera shake which is found in all
previous optical Image Stabilizer mechanisms, as well as a new
acceleration sensor that determines the amount of shift-based camera
shake.
Hybrid IS also employs a newly developed algorithm that combines the
output of the two sensors and moves the lens elements to compensate
for both types of movement. Hybrid IS dramatically enhances the
effects of Image Stabilizer especially during macro shooting, which is
difficult for conventional image stabilisation technologies.
