Photography for Multimedia

B.Sc. (Hons) Multimedia Computing

Media Technologies

Photographic Principles

Agenda

Photography Evolution Camera Types Lens Principles Exposure Control Lenses

B.Sc. (Hons) Multimedia Computing

Media Technologies

The first photograph (Niepce, 1816)

Early photograph (Daguerre, 1830’s)

35mm:Nikon F2AS (Film)

35mm : Nikon F6 (Film)

35mm:Nikon DX2s Digital (12MP)

Medium Format: Film 6 x 6 cm

Medium Format: Digital 39MP

Large Format Film:5x4 & 10x8

Large Format Digital

Premise

Even the World’s most sophisticated camera is in essence just a light-tight box

Fundamentals

Expose the light sensitive material with a quantity of light for a given time

Film, or… Digital – it’s the same concept

Camera Principles

light

Light sensitive material

Light-tight enclosure

Camera Obscura

The Pinhole Camera

Camera Principles

Scene Image

Pinhole Camera

Resulting image is mirrored and inverted

Small aperture results in very long exposures

Light Rays

Camera Principles

Scene Image

Pinhole Camera

Increasing the pinhole size provides more light to shorten exposure times but introduces distortion of light rays resulting in poor image qualityLight Rays

Lens Principles

Scene Image

Simple Lens

Simple lens refracts light to reduce distortions

Light Rays

Lens Principles

Scene Image

Compound Lens

Compound lens designed to control variety of lens aberrations which affect both image sharpness and colour

Light Rays

Camera Elements

Lens Shutter Viewfinder system Focusing mechanism Transport Light Meter

Basic Elements of a Camera

viewfinder

shutter aperture

lens

focusing mechanism

light sensitive medium

transport

Camera Types

Rangefinders Single Lens Reflex (SLR) Twin Lens Reflex (TLR) Monorail

Rangefinder

Single Lens Reflex

Twin Lens Reflex (Medium Format)

Taking Lens

Viewing Lens

Monorail: 5 x 4 & 10 x 8

35mm v Medium Format

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

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

Aperture Control

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

Exposure Balance

f stop shutter speed

Sensitivity of film

f 5.6 1 / 500th

100 ISO

Exposure Balance

f 8 1 / 250th

200 ISO

f 11 1 / 250th100 ISO

200 ISO

f 8 1 / 500th

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

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

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

Standard Lenses (35mm)

50mm f1.250mm f1.8 50mm f1.4

Wide Angle Lenses

15mm F 3.528mm F 2.8 20mm F 3.5

Telephoto

85 mm F 2 85 mm F 1.4 300 mm F4.5

Lens Features: Angle of View

Angle of View for 35mm

Shorter focal length lenses have angle of view which gives steeper perspective

Longer focal length lenses have narrow angle of view which gives flatter perspective

50mm provides natural perspective for the 35mm format

Advanced features

Autofocus Image stabilisation Intelligent recognition of faces and

scenes

Autofocus (1) – Blurred image

Autofocus (2) – sharp image

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.

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)

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.

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.

Intelligent recognition

Equipment Taking pictures

Cameras (bodies) Lenses: fix focal and zoom lenses Lightmeters Flashguns Motordrives Gadgets (tripods, filters, bags, close-up equipment

Developing pictures Darkroom ( dry and wet equipment) Developing tanks, spools Enlargers ( lenses)

References

B.Sc. (Hons) Multimedia Computing

Media Technologies

Digital Multimedia 3rd EditionChapman N. Chapman J. Wiley. 2004

http://www.nikon.com http://www.olympus..com http://www.pentax.com http://www.minolta.com http://www.canon.com