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`Apple Inc. v. Corephotonics
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`Langford'’s
`Advanced
`Photography
`
`Seventh Edition
`
`APPL-1009 / Page 2 of 26
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`APPL-1009 / Page 2 of 26
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`

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`_Langford'’s
`Advanced
`Photography
`
`Seventh Edition
`
`Michael Langford FBIPP, HonFRPS
`Royal College of Art, London
`
`Efthimia Bilissi MSc PhD AIS ARPS
`Senior Lecturer
`
`University of Westminster, London
`
`Contributors
`Elizabeth Allen BSc MSc
`Course Leader BSc (Hons) PhotographyandDigital Imaging
`University of Westminster, London
`
`Andy Golding
`Head of Department of Photography and Film
`University of Westminster, London
`
`Hani Muammar BSc MSc PhD MIET
`Senior Scientist
`
`Kodak European Research
`
`Sophie Triantaphillidou BSc PhD ASIS FRPS
`Leader Imaging Technology Research Group
`University of Westminster, London
`
` AMSTERDAM ® BOSTON ® HEIDELBERG ® LONDON ® NEW YORK ® OXFORD
`
`PARIS ® SAN DIEGO ® SAN FRANCISCO ® SINGAPORE ® SYDNEY ® TOKYO
`Focal Press is an imprint of Elsevier
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`<
`ELSEVIER
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`aa APPL-1009 / Page 3 of 26
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`Focal
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` Focal Pressis an imprint of Elsevier
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`
`
`
`
`Working together to grow
`libraries in developing countries
`www.elsevier.com | www.bookaid.org | www.sabre.org
`
`
`
`ELSEVIER
`BOONE
`Sabre Foundation
`
`
`
`First published 1969
`Secondedition 1972
`Third edition 1974
`Fourth edition 1980
`Fifth edition 1989
`Reprinted 1992, 1993, 1994, 1995
`Sixth edition 1998
`Reprinted 1999, 2001, 2003, 2004, 2005, 2006
`Seventh edition 2008
`
`Copyright © 2008, Pamela Langford, Dr. EfthimiaBilissi.
`Contributors: Elizabeth Allen, Dr. Sophie Triantiphilidou, Andy Golding and Dr. Hani Muammar.
`Published byElsevier Ltd. All right reserved
`The right of Dr. Efthimia Bilissi, Michael Langford, Elizabeth Allen, Dr. Sophie
`Triantiphilidou, Andy Golding and Dr. Hani Muammar to be identified as the authors
`of this work has beenasserted in accordance with the Copyright, Designs and Patents Act 1988
`Nopartof this publication may be reproduced,storedin a retrieval system or transmitted
`in any form or by any means electronic, mechanical, photocopying, recording or
`otherwise withoutthe prior written permission of the publisher
`Permissions may be sought directly from Elsevier’s Science & Technology Rights
`Departmentin Oxford, UK: phone:(+44) (0) 1865 843830; fax: (+44) (0) 1865 853333;
`email: permissions@elsevier.com. Alternatively you can submit your request online by
`visiting the Elsevier websiteat http://elsevier.com/locate/permissions, andselecting
`Obtaining permission to use Elsevier material
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`Noresponsibility is assumed by the publisher for any injury and/or damage to persons or
`property as a matter of products liability, negligence or otherwise, or from any use or
`operation of any methods, products, instructions or ideas contained in the material herein.
`Becauseof rapid advancesin the medical sciences, in particular, independentverification
`of diagnoses and drug dosages should be made
`British Library Cataloguing in Publication Data
`Langford, Michael John, 1933—
`Langford’s advanced photography. — 7th ed.
`1. Photography
`I. Title II. Bilissi, Efthimia II. Langford, Michael John,
`1933-. A dvanced photography
`771
`
`Library of Congress Number: 2007938571
`ISBN: 978-0-240-52038-4
`
`For information onall Focal Press publications
`visit our website at www.focalpress.com
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`Picture credits
`Introduction
`
`xiii
`aa
`
`
`
` Al
`Amateur and professional photography
`Differences in approach
`ee
`How photographs are read
`fa.
`a Markets for professional photography
`/
`Roles within a photographic business
`ig Turning professional
`
`
`4
`3
`2
`11
`13
`
`14
`
`Summary
`
`2
`
`es
`
`2 Camera equipment
`
`15
`
`15
`16
`24
`26
`26
`28
`35
`38
`39
`41
`
`42
`
`42
`47
`48
`Ho
`56
`63
`64
`65
`67
`
` Camera design
`
`
`Image format
`Specialized accessories
`Which one is best?
`Avoiding camera failures
`The digital revolution
`Digital camera equipment
`Comparing digital and silver halide camera equipment
`Summary
`Projects
`
`3 Choosing lenses
`
`The lens designer’s problems
`Checking lens image quality
`Understanding modulation transfer function
`Buying lenses
`Special lens types
`Influences on image sharpness
`Using lenses created for 35mm systems on DSLRs
`Summary
`Projects
`
`APPL-1009 / Page 5 of 26
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`The human visual system
`Light sources and their characteristics
`Colour temperature
`Standardilluminants
`
`GOSSEN
`
`is]
`
`Classification of colour
`
`How wesee colour
`
`Summary
`Projects
`
` CONTENTS
`Corollaae Light and colour
`
`Spectral sensitivity
`Reciprocity failure
`Product coding
`Special materials
`Summary
`Projects
`
`Film design
`Choosing films
`Understanding technical descriptions
`Film MTF
`
`Characteristic curves
`
`An introduction to image sensors
`Alternative sensor technologies
`Image artefacts associated with sensors
`Summary
`Projects
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`APPL-1009 / Page 6 of 26
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`
`
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`Size of light sources
`Direction and angle of light
`
`Distribution oflight
`
`Contrast and exposure
`
`Colour and colour temperature
`
`Practical control of colour
`
`Guidelines for lighting
`
`Lighting equipment
`Lighting principles in practice
`Summary
`
`Projects
`
`Practical influences
`
`Tone control theory
`
`Precision measurement of exposure
`
`The zone system
`Putting the zone system to work
`Limitations to the zone system
`Tone changesafter film processing
`Controls during enlarging
`
`Summary
`
`Projects
`
`129
`
`132
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`133
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`134
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`137
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`139
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`140
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`142
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`144
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`154
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`155
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`178 APPL-1009 / Page 7 of 26
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`156
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`159
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`163
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`165
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`171
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`173
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`174
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`176
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`177
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`APPL-1009 / Page 7 of 26
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`
`
`Photo-journalism/documentary
`Portraiture
`Weddings
`Landscapes
`Architecture
`Built studio sets
`Studio stilllifes
`Natural history
`Aerial subjects
`Night skies
`Summary
`Projects
`
` Sport and action
`
`
`10 Digital imaging systems
`
`The computer workstation
`Inputs
`Types of scanners
`Scanner characteristics
`Setting up the scanner
`Image outputting — Displays
`Characteristics of display systems
`Image outputting — Digital printers
`Printer characteristics
`Summary
`Projects
`
`APPL-1009 / Page 8 of 26
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`
`
`
`Whatis workflow?
`General considerations in determining workflow
`Capture workflow
`Digital image files
`Choosing file format
`Image compression
`Properties of common image file formats
`Image processing
`Image processing workflow
`Digital colour
`
`Summary
`
`Projects
`
`The processes themselves
`Points to watch
`
`Equipment
`Making a choice
`Process control
`
`Silver recovery
`Colour printing equipment
`Print materials
`Negative/positive colour printing
`Positive/positive colour printing
`Shading and printing-in
`Making a ring-around
`Additional points to watch
`Colour/exposure analysing aids
`Other colour lab procedures
`
`Summary
`
`Projects
`
`229
`
`229
`
`233
`
`237
`
`240
`
`241
`
`246
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`247
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`249
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`256
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`264
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`266
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`267
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`272
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`275
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`279
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`280
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`284
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`285
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`288
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`289
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`292
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`293
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`293
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`295
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`296
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`298
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`299
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`APPL-1009 / Page 9 of 26
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`
`
`Photographing the invisible
`Underwater photography
`Panoramic photography
`Stereo photography
`‘Hand-made’ image processes
`Summary
`Projects
`
`Reproduction of the printed page
`Supplying photographsfor reproduction
`Picture libraries
`Images on the World Wide Web
`Multimedia
`Permanence, storage and archiving
`Summary
`Projects
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Starting out
`Working as an assistant
`Becoming a photographer
`Running a business
`Book-keeping
`Charging for jobs
`Commissioned work
`Copyright
`Marketing your business
`Summary
`
`365
`
`369
`
`APPL-1009 / Page 10 of 26
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`APPL-1009 / Page 10 of 26
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`

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`Appendices
`
`Appendix A: Optical calculations
`Appendix B: Gamma and average gradient
`Appendix C: Chemical formulae: Health and safety
`Appendix D: Lighting and safety
`Appendix E: Batteries
`Appendix F: Colour conversionfilter chart
`Appendix G: Ring around chart
`
`Glossary
`
`Index
`
`372
`
`377
`
`377
`
`378
`
`379
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`380
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`370
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`370
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`372
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`407 APPL-1009 / Page 11 of 26
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`
`loadingfilm. Fitting a hood of correct diameter will reducethe risk of somethinggettingin front
`of the lens.
`Rememberthe value of having an instant-picture back,to allow you to confirm visually that
`lens and bodyare working correctly — plus checkinglighting, exposure and composition — at any
`time during a shoot. Someprofessional photographershabitually expose oneinstant pictureat
`the beginning and anotheratthe end of every assignment, as insurance.It is also a good idea to
`carry another complete camera (a 35mm SLR,for example) as emergency back-up.
`
`The digital revolution
`
`he first patents for devices capturing imageselectronically werefiled as far back as 1973.
`Kodak created a prototype digital camera in 1975 using a charge-coupled device (CCD),
`recording black and white images on to digital cassette tape; howeverit was built to test
`the feasibility of digital capture usingsolid state sensors, rather than as a camera for manufacture
`(duetoit’s bulky size and a weight of nearly 3.6 kg). It was not until 1981 that Sony developed a
`camera using a CCD,suitable to be hand-held and available to the consumer. Thebirth ofdigital
`still cameras as we know them today happenedin 1988, when Fuji showcasedtheir camera, the
`DS-1P, at Photokina. Early digital formats could not compete with their film equivalents in terms
`of cost or quality; digital camerasas a practical option for consumerswerenotreally available
`until the mid-1990s. Since then the digital market and technologies have grown exponentially.
`The moveto digital imaging by many photographershas involved a preceding step via
`‘hybrid’ imaging - thatis, capture onfilm followed by digitization using a scanner. However,
`in the last ten years, huge advances in sensor technology, computing capabilities and the
`widespread adoption of broadband (ADSL) Internet connection by the consumer have meant
`that digital imaging hasfinally arrived. For example, most householdsin Britain now ownat
`least one computer and the majority of new mobile phoneshavea built-in digital camera. The
`digital camera market has therefore been advanced by the consumer market and of course the
`widespread useof imaging on the Internet.
`Immediate results and the ability to easily manipulate, store and transmit images have
`becomea priority in manydisciplines, with somesacrifice in the quality that we expectin our
`images.In the professional market there have also been compromises betweenversatility of
`systems and image quality, but progress towards the uptakeofentirely digital systems has been
`somewhatslower. In sometypes of photography imagequality is still more important than
`speedy processing andthe lack of equipmentavailable in larger formats has meantthatfilm-
`based systemsare still common.Sports photography and photojournalism, however, have
`embraced a predominantly digital workflow from captureto output.
`
`Instead of exposing onto silver halide coated film, currently the majority of digital cameras contain
`oneof twotypesoflight sensitive array, either a charge-coupled device, known as a CCD, which
`is commonin earlier digital cameras, or fast overtakingit, the complementary metal-oxide
`semiconductor or CMOSimagesensor.Thesensoris in the same position asthefilm in an analogue
`camera. Manyofthe key external features of digital and film camerasare similar, but digital cameras
`have a whole otherlayer of complexity in terms of user controls in the camera software.
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`Both types of digital image sensorare based on the same material, silicon, which when
`amounts of other elements, can be madesensitive to light. When exposed to
`‘doped’ with small
`light,
`it produces @ small amountofelectrical charge proportionalto the amountoflightfalling
`it, whichis stored, transported off the sensor, convertedinto a stream of binary digits (1’s or
`on
`0’s, hence the name ‘digital imaging’), and written intoa digital imagefile. The processis a
`complex one, and the structure and operation of the sensoris covered in more detail in Chapter6.
`There are many fundamentaldifferences betweenfilm-based anddigital imaging, notleast that
`where a frame of film both captures andstores the image, andis therefore not reusable, a digital
`sensor captures the image, butit is then transported awayandstored as an image‘file’
`somewhereoff the chip. Theoretically, if an imagefile is not compressed and is continually
`copied and migrated across different media, it is permanent and can be reproduced as many
`times as required, without any degradation in quality.
`
`
`
`
`
`eS
`
`Eee
`
`
`
`:
`
`ae
`:
`Dae sone erie
`; Ang
`
`8s
`
` ees
`
`Sampled images
`Anotherkey difference between digital and analogue imagingis the fact that the digital image is
`tured across a regular grid of pixels (Picture Elements). Each pixel is an individual image-
`cap
`sensing element, which produces
`a response based on the average
`amountoflight falling onit.
`Wherefilm ‘grains’ are distributed
`randomly through a film emulsion
`and overlap each otherto create
`the impression of continuous
`tones, pixels are non-overlapping
`and if a digital image is magnified,
`individual pixels will become very
`evident. Digital images are a
`discrete representation. This is
`further accentuated by the fact
`that pixels are not only discrete
`units across the spatial
`dimensions of the image, but that
`they can only take certain values
`and are solid blocks of colour. The
`processofallocating a continuous
`input range of tone and colour to
`
`APPL-1009 / Page 13 of 26
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`/
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`-_|
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`.
`
`:
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`4
`
`eas
`ee
`
`
`=
`
`a discrete output range which
`changesin steps, is known as
`quantization (see Figure 2.12). The
`whole pixel will be the same
`colour, regardless of the fact that
`Figure 2.12 Sampling and quantizationin a digital image: (a) The imageis
`the light falling on it in the
`spatially sampledinto a grid ofdiscrete pixels; (b) The continuous colour range from
`original scene may havevaried
`the original scene is quantized into a limited set of discrete levels, based on the bit
`
`depth of the image.
`acrossthe pixel area.
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`APPL-1009 / Page 13 of 26
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`colour values. The stepped changesin colour values and the non-overlapping natureofthe pixels
`are limiting factorsin the quality and resolution ofa digital image. The spatial sampling rateis
`determined by the physical dimensionsof the sensor. The quantization levels depend upon the
`sensitivity of the sensor, analogueto digital conversion, image processing in the capture device
`and ultimately on the outputfile format.
`
` A digital imageis therefore ‘sampled’ both acrossits physical dimensions andin terms of its
`
`whyfilm grain is important, although a poor quality lens, as any photographerknows,is a
`primary causeofloss of sharpness. There are a numberof measures of resolution, but two
`commonly used and covered in moredetail in the chapters on lenses and film are resolving power
`and Modulation Transfer Function (MTF).
`Whereresolutionin traditional film-based imagingis well-defined, the different ways in
`whichthe term is used andits range of meanings when referring to digital systems can be
`confusing.It is helpful to understand these differences and to be clear about what resolution
`meansat different stages in the imaging chain. You will see the term explained and used in
`different contexts throughout this book, but to summarize.
`Fundamentally, digital images do not have an absolute resolution, but a numberofpixels.
`The level of detail that is represented will depend upon howthis number of pixels are captured
`or viewed. Therefore, imageresolution is often quoted in pixel numbers, calculated by numberof
`rows X numberof columns. It may bereferred to in terms of megapixels, a megapixel being a
`million pixels; this is a value often quoted by digital camera manufacturers.
`At different stages in the imaging chain, resolution may also be measured as a function of
`distance. Scanner or monitorresolution, for example, may be quoted in terms of numbers of
`pixels per inch (ppi) and printers are often specified in terms of dots perinch(dpi). The
`combinationsof these different resolutions in the output image determinethefinal image quality
`and also output imagesize. These relationships are examined in moredetail in the chapter on
`digital imaging systems. When quoted by manufacturers of these devices, they will usually quote
`the upperlimit for that device, althoughit will be possible to capture and output imagesat a
`range of resolutions below this.
`A clever trick that manufacturers often use to enhancethe apparentcharacteristics of
`their devices is to quote interpolated resolution. This applies to cameras and scanners. The
`actual(or optical) resolution of a device is defined by the numberofindividual elements and
`their spacing; howeverit is possible to rescale an imagebyinterpolating values between the
`actual values,in effect creating false pixels. The visualeffects of this are a slight blurring of
`the image, becausethe interpolation process averages adjacent pixels values to create the
`new pixels.
`
`Resolution is the capability of an imaging system to distinguish between two adjacent points in
`an image andis a measureofthe detail-recordingability of a system. It defines how sharp your
`images will appear and whatleveloffine detail will be represented. In any imaging system thisis
`affected by every componentthrough whichlight passes;in a film-based system the lens and the
`film will be the key factors, but anything placed overthe lens or sensor, suchasa filter, may also
`
` affect it. It is usually the resolution of the imagesensorthatis the ultimate limiting factor, whichis
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`In camerastoo, the effective resolution may be quoted, although manufacturers may not
`identifyit as anything other than resolution. Again,this is a form of interpolated resolution, but
`refers in this case to the fact that in the majority of cameras, the sensor is filtered, so that each
`pixel captures only one colour, usually red, green or blue. To obtain the other colour values at
`eachpixelin the captured RGB image, adjacent pixels of each colour are used and the missing
`values interpolated. As with all interpolation there is an associated blurring and loss of quality.
`There is an exception, however: in the last few years, a new sensor, the Foveon™chip, has been
`developed, which captures colourat different depthsin the sensor and therefore captures all
`GB values at every pixel. This sensor, however,is only available in a few cameras
`three R
`ly on the market, so for the majority, effective resolution still applies.
`current
`
`
`
`How many pixels?
`Whenbuying a digital camera, resolution is a primary consideration, and a key factor in image
`quality, howeverthe previous discussion indicates the confusion around the subject. The highest
`numberof megapixels does not necessarily represent the highest quality or automatically mean
`that the largestlevel of detail will be reproduced. Otherfactors are involved as well.
`The pixel pitch, whichis the centre-to-centre distance between pixels andrelates to the
`overall pixelsize, is important in determining the maximumlevelof detail that the system is able
`to reproduce. Tied up with this however, is the imaging area of each pixel, which in some
`cameras may be as low as 20%, due to the inclusion of other components and wiring at each
`pixel and channels in betweenimagingareas. Also, the pixel shape; whether there are
`microlenses above each pixel to focus and maximizethe light captured; even the interpolation
`algorithmsusedin calculating missing colour values, which vary between manufacturers, these
`will have an effect on final image resolution. These factors combineto influence the shape of the
`sensor’s MTFandit is this that is a far better indicator of how well a camera will perform. The
`quality of the lens must additionally be taken into account. Finally, and really important, is the
`pixel size relative to the overallsize of the imaging area on the sensor.
`Whatthe above discussion highlights is the complicated nature of resolution as a measure
`of image quality in digital cameras. Do not make a choice based solely on the numberof
`megapixels. Make informed decisions instead, based on results from technical reviews and from
`your own observations throughtesting out different camera models. You needto decide
`beforehand how you wantto use the camera, for what type of subjects, what type of
`photography and what type of output.
`Bearingall this in mind,it is still useful to have an idea of the physical size of output images
`that different sensor resolutions will produce. Print resolution requirements are much greater
`than thosefor screen images. Althoughit is now widely accepted that images of adequate
`quality can be printed at 240 dpi, or perhaps even lower, a resolution of 300 dpi is commonly
`given as required output for high-quality prints. Some picture libraries and agencies may,
`instead of specifying required imagesize in terms of output resolution and dimensions,state a
`requiredfile size instead. It is important to note that this is uncompressed file size. It is also
`necessary to identify the bit depth being specified as this will have an influenceonfile size.
`Figure 2.13 provides some examples for printed output.
`
`
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`APPL-1009 / Page 15 of 26
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`
`
`INPUT: CMOS or CCD image sensor
`
`Megapixels
`
`16.6
`12.7
`10.1
`8.2
`re
`
`Sensorsize
`Sensorresolution
`mm
`Pixels
`w
`h
`w
`36
`3328
`4992
`35.8
`2912
`4368
`22.2
`2592
`3888
`22.5
`2336
`3504
`5.7
`2304
`3072
`Sensorresolution, dimensions,file size and printed output.
`
`OUTPUT:8 bits per channel RGB images
`printed at 300 dpi
`File size
`Outputprint size
`MB
`inches
`w
`16.6
`14.6
`13.0
`11.7
`10.2
`
`47.5
`36.4
`28.8
`23.4
`20.3
`
`h
`24
`23.9
`14.8
`15
`4.3
`
`Digital image capture is a complex process. The signal from the sensor undergoes a numberof
`processesbeforeit is finally written to an imagefile. The processes are carried out either on the
`sensoritself, in the camera’s built-in firmwareor via camera software, in responseto user
`settings. They are designedto optimize the final image accordingto the imaging conditions,
`camera and sensorcharacteristics and output required by the user. The actual processes and the
`waythey are implementedwill vary widely from camera to camera. Some are common to most
`digital cameras however. Theywill be covered in moredetail in other chapters, but are
`summarized below. Theyinclude:
`
`Signal amplification: This may be applied to the signal before or after analogue-to-digital conversion;this is a
`result of auto exposuresetting within the camera and ensures that the sensor usesits full dynamic range.In
`effect the contrast of the sensoris corrected for the particular lighting conditions.
`Analogue-to-digital conversion: The process of sampling and converting analogue voltagesinto digital values.
`Noise suppression: There are multiple sources of noise in digital cameras. The level of noise depends upon the
`sensor type and the imaging conditions. Adaptive imageprocessing techniques are used to removedifferent
`types of noise. Noise is enhancedif the camera gets hot (the sensoris sometimes cooled to reduce the noise
`levels), also if long exposures or high ISO settings are used.
`Unsharp maskfiltering: Used to sharpen edges and counteractblurring caused by interpolation.
`Colourinterpolation (demosaicing): This is the processof calculating missing colour values from adjacent colour-
`filtered pixels.
`
`Theseare sensorspecific, in-built and not user controlled. Additionally, settings by the userwill
`implementprocessescontrolling:
`
`White balance: The image colours (the gamut) are shifted to correct for the white oftheilluminant and ensure
`that neutrals remain neutral. White point setting maybe viaalist of preset colour temperatures, calculated by
`capturing a frame containing a white object, or measured by the camera from the scene.In film cameras,this
`requires a combination ofselecting film for a particular colour temperature and using colour-balancing or colour-
`correction filters.
`/SO speed: The sensitivity of the sensoris set by amplifying the signal to produce a required range of output
`values underparticular exposure conditions. Againin film cameras, this would be achieved by changingto a film
`
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`

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`of a different ISO. ISO settings usually range from 100 up to 800. Some cameras will allow ISO values up to
`1600 or even 3200. The native ISO of the sensor howeveris usually 100-200. Anything above this is a result of
`amplification. Amplifying the signal also amplifies the noise levels and this may show upas coloured patternsin
`flat areas within the image.
`sure and the image histogram: This is a process of shifting the output values by amplification of the input
`Expo.
`maximum range of output values is produced,ideally without clipping the values at the
`signal, to ensure that the
`ge. The actual exposure measurements are taken through the lensas fora film camera
`top or bottom of the ran
`and image processing takes care of the rest. To optimize this process the image histogram is provided in SLRs
`and larger formats to allow exposure compensation and user adjustment. This is a graphical representation,a
`bar chart of the distribution of output levels and is an accurate method of ensuring correct exposure and
`contrast, as viewing the imagein the low resolution and poor viewing conditions of the LCD preview window
`may produce inaccurate results. In particular, it can be difficult to tell in the preview whenhighlight values are
`clipped, a situation to be avoided. The histogram will easily alert you to this and allow you to make necessary
`adjustments for a perfect exposure. For more information on exposure and the histogram, see Chapter 11.
`Image resolution: Many cameras, will allow a numberofresolution settings, lower than the native resolution of
`the camera to save onfile size. These lowerresolutions will be achieved by down-sampling,either dropping pixel
`values completely if the imageis being downsampledby a factorof 2, or by interpolating values from the
`existing sensor values.
`Capture into a standard colour space: With the necessary adoption of colour-managed workflow,a numberof
`standard colour spaces have emerged. Capturing into a standard colour space means that the image gamut has
`the best chance of being reproducedaccurately throughout the imaging chain (see Chapter 11 for further details).
`The two most commonly used standard colour spacesin digital camerasare sRGB and Adobe RGB (1998). sRGB is
`optimized for images to be viewed onscreen. Theslightly larger gamut of Adobe RGB encompassed the rangeof
`colours reproduced by mostprinters andis therefore seen as more suitable for images that are to be printed.
`File quality (if image is to be compressed) andfile format: Most cameraswill offer a range of different outputfile
`formats. The most common onesin digital cameras are JPEG, TIFF and RAW formats. The merits of these different
`formats are discussed in detail in Chapter 11. Of the three, JPEG is the only one that compresses the image,
`resulting in a loss of information. A quality setting defines the severity of theloss,file size and resulting artifacts.
`TIFF and RAW are uncompressed and thereforefile sizes are significantly larger. TIFF is a standard format that may
`be used for archiving images without loss. RAW is more than a file format, as it results in almost unprocessed data
`being taken from the camera. With RAW images, the majority of the image processing detailed aboveis
`performed by the user in separate software after the image has been downloaded from the camera.
`
`e
`
`°
`
`This short summary highlights someofthe differences between using film and working
`digitally. The immediacyof results from digital camerasis somewhat counterbalanced by the
`numberof settings required by the user before image capture. However it also highlights the
`high degree of control that you have. Manyof the adjustments that would have to be performed
`optically with a film-based system, or by changing film stock, may be achieved bytheflick of a
`switch or the press of a button.
`
`Digital sensor sizes
`Oneofthe initial problems in producing digital cameras with comparable image quality to film
`wasthe difficulty and expense in manufacturing CCDsof equivalent areas. Manydigital cameras
`have sensors whichare significantly smaller than 35 mm format. Thesizes are often expressed as
`factors, and they are based on the diagonal of a 1 in. optical image projected onto a sensor by a
`lens, which is close to 16mm. Examplesof the actual dimensions of some image sensors are
`
`shownin Figure 2.14, compared to typical film formats.
`
`APPL-1009 / Page 17 of 26
`
`APPL-1009 / Page 17 of 26
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`

`

`Sensor/format
`
`Film
`35mm
`120mm
`
`Large format
`
`Horizontal Vertical Diagonal Aspect Sensor Type
`(mm)
`(mm)
`(mm)
`Ratio
`
`36.0
`60.0
`
`120.0
`
`24.0
`60.0
`
`43.3
`84.9
`
`101.6
`
`162.6
`
`3:2
`11
`
`5:4
`
`Film
`Film
`
`Film
`
`1.9
`4.0
`4.8
`5:3
`6.6
`9.6
`14.8
`15.7
`
`3.2
`6.7
`8.0
`8.9
`11.0
`16.0
`26.7
`28.4
`
`4:3
`4:3
`4:3
`4:3
`4:3
`4:3
`3:2
`3:2
`
`CMOS
`CCD/CMOS
`CCD/CMOS
`CCD/CMOS
`CCD/CMOS
`CCD/CMOS
`CMOS
`CCD
`
`Digital sensors — consumer market
`1/5
`2.6
`1/2.7
`5.4
`1/2
`6.4
`1/1.8
`te
`2/3
`8.8
`1
`12.8
`1.8*
`22.2
`1.8”
`23.7
`Digital sensors — professional market
`CMOS
`3:2
`43.3
`24.0
`Full frame 35 mm
`36.0
`Full frame CCD
`1:1
`52.2
`36.9
`Medium/large format back
`36.9
`Full frame CCD
`4:3
`60.0
`36.0
`Medium/large format back
`48.0
`Trilinear array CCD Scanning back
`4:3
`61.0
`36.9
`Medium/large format back
`49.0
`Trilinear array CCD Scanning back
`4:3
`120.0
`72.0
`Large format back
`96.0
`Trilinear array CCD Scanning back
`4:3
`130.6
`84.0
`Large format back
`100.0
`“There are a variety of different sensors labelled 1.8 and sizes vary slightly between manufacturers
`
`
`
`Dimensionsof typical film formats and digital image sensors.
`
`The small sensorsizes meanthat in most digital cameras the focal lengths of lenses are
`significantly shorter thanin film-based systems. This has a numberof implications.Firstofall,it
`meansthat in the compact market, it has been possible to make much smaller camerabodies,
`and this is the reason that miniature cameras have proliferated (it has also madethetiny
`cameras used in mobile phonesa possibility, see below). As for film camera formats, a shorter
`focal length means greater depthoffield. The result ofthis is that using a shallow depthoffield
`for selective focus on a subject is much moredifficult in digital photography, because moreoften
`than not everything in frame appears sharp. Thisis one of the reasonsthat professionals often
`prefer a full-frame sensorof the samesize as the equivalent film format, becausein this case the
`lens focal lengths and depthoffield will be the sameas forfilm.
`A further implication of the smaller sensorsis that lens of focal lengths designed forfilm
`formats will produce a smaller angle of view when placed on a digital camera with a smaller
`sensor. This meansthat standard focal length lenses effectively becometelephotolenses(see
`Figure 2.15). The problem affects small-format SLRs, wherelenses from the equivalentfilm
`format might be used, and also the larger formats whenusing digital backs with a smaller
`imaging area than the associatedfilm back.It can also cause confusion when comparing the
`zoom lenses of two cameraswith different-sized sensors. Effective focal length is sometimes
`quoted instead. This expressesthe focal length as the sameas a focal length ofa lens onafilm
`camera, usually 35 mm, based on an equivalent angle of view.
`
`APPL-1009 / Page 18 of 26
`
`APPL-1009 / Page 18 of 26
`
`

`

`Projected imageis circular and
`covers the diagonal of the format
`
`y
`
`
`
`Film: 24 x 36mm
`image area using a >
`50 mm focal length
`.
`lens with 135film
`
`
`
`
`
`14 x 22mm image
`area of a 1.8 digital
`sensor gives a smaller
`angle of view. The
`effective focal length of
`the lens becomes 80 mm
`
`Figure 2.15 Changein angle of view as a result of smaller sensorsize and focallength. Manufacturers often quote ‘effective focal length’
`for digital lenses, which relates thefield of view ofthelens to that provided by the focal length of thelens in the relatedfilm format.
`Digital camera equipment
`igital camera equipmentisless easily classified by image
`format than film simply becauseof the hugevariation in
`sensor size. Cameras can, however, be put into broad
`categories based upon the market for which they are aimed and
`like film cameras, this dictates the level of sophistication and cost
`of the equipment.
`The equipmentfalls into a numberof main types(see
`Figure 2.16):
`
`1
`
`Specially designed compact type cameras for point-and-shoot
`snapshots. Mobile phone cameras — with fewerfeatures — can also be
`included in this category.
`2 Hybrid cameras. There are a range of different designs, but they often
`bridge the gap between compacts and SLRs, containing many of the
`featur