Photography for Multimedia B.Sc. (Hons) Multimedia ComputingMedia Technologies Photographic Principles

Agenda Photography Evolution Camera Types Lens Principles Exposure Control Lenses B.Sc. (Hons) Multimedia ComputingMedia 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 SceneImage Pinhole Camera Resulting image is mirrored and inverted Small aperture results in very long exposures Light Rays

Camera Principles SceneImage Pinhole Camera Increasing the pinhole size provides more light to shorten exposure times but introduces distortion of light rays resulting in poor image quality Light Rays

Lens Principles SceneImage Simple Lens Simple lens refracts light to reduce distortions Light Rays

Lens Principles SceneImage 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 shutteraperture 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 stopshutter speed Sensitivity of film f 5.61 / 500th 100 ISO

Exposure Balance f 81 / 250th 200 ISO f 111 / 250th 100 ISO 200 ISO f 81 / 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 f1.850mm f1.4

Wide Angle Lenses 15mm F 3.528mm F 2.820mm F 3.5

Telephoto 85 mm F 285 mm F 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 ComputingMedia Technologies Digital Multimedia 3rd Edition Chapman N. Chapman J. Wiley