APPL-1009/Page 1 of 26
`Apple Inc. v. Corephotonics
`
`

`

`Lengfohd’e
`Advanced
`Photography
`
`Seventh Edition
`
`APPL-1009 / Page 2 of 26
`
`
`
`APPL-1009 / Page 2 of 26
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`

`

`Langfond’e
`Advanced
`Photography
`
`Seventh Edition
`
`Michael Langfond FBIPP,I-IonFRPS
`Royal College of Art, London
`
`Efthimia Bilieei MSc PhD AIS ARPS
`Senior Lecturer
`
`University of Westminster, London
`
`Conthibutor‘e
`Elizabeth Allen BSc MSc
`Course Leader BSc (Hons) Photography and Digital Imaging
`University of Westminster, London
`
`Andy Golding
`Head of Department of Photography and Film
`University of Westminster, London
`
`Hani Muarnrnar“ BSc MSc PhD MIET
`Senior Scientist
`
`Kodak European Research
`
`Sophie Tr‘iantaphillidou BSc PhD ASIS FRPS
`Leader Imaging Technology Research Group
`University of Westminster, London
`
` AMSTERDAM ° BOSTON ° HEIDELBERG ° LONDON ' NEW YORK ° OXFORD
`
`1s
`
`ELSEVIER
`
`PARIS ° SAN DIEGO ' SAN FRANCISCO ° SINGAPORE ° SYDNEY ' TOKYO
`Focal Press is an imprint of Elsevier
`
`Press
`
`Focal
`
`APPL-1009 / Page 3 of 26
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`APPL-1009 / Page 3 of 26
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`

`

`
`
`First published 1969
`Second edition 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. Efthimia Bilissi.
`Contributors: Elizabeth Allen, Dr. Sophie Triantiphilidou, Andy Golding and Dr. Hani Muammar.
`Published by Elsevier 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 been asserted in accordance with the Copyright, Designs and Patents Act 1988
`No part of this publication may be reproduced, stored in a retrieval system or transmitted
`in any form or by any means electronic, mechanical, photocopying, recording or
`otherwise without the prior written permission of the publisher
`Permissions may be sought directly from Elsevier’s Science & Technology Rights
`Department in 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 web site at http://elsevier.com/locate/permissions, and selecting
`Obtaining permission to use Elsevier material
`Notice
`
`No responsibility 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.
`Because of rapid advances in the medical sciences, in particular, independent verification
`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
`1. Title II. Bilissi, Efthimia III. Langford, Michael John,
`1933—. A dvanced photography
`771
`
`Library of Congress Number: 2007938571
`ISBN: 978—O«240—52038—4
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`For information on all Focal Press publications
`visit our website at www.focalpress.com
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`APPL-1009 / Page 4 of 26
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`APPL-1009 / Page 4 of 26
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`

`

`Picture credits
`Introduction
`
`xiii
`xv
`
`
`’1 Amateur and professional photography
`
`
`
`
`\ F
`fiyr
`Kg;
`I,
`(1
`
`\ ll
`
`Differences in approach
`How photographs are read
`Markets for professional photography
`Roles within a photographic business
`Turning professional
`
`Summary
`
`2 Camera equipment
`
`
`
`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 35 mm systems on DSLRs
`
`Summary
`
`Projects
`
`’I
`3
`5
`’I
`’l
`13
`
`14
`
`’I 5
`
`’l5
`
`18
`
`24
`26
`
`28
`28
`
`35
`
`38
`
`39
`
`4’l
`
`42
`
`42
`
`47
`
`48
`
`55
`
`55
`
`83
`
`84
`
`85
`
`87
`
`APPL-1009 / Page 5 of 26
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`APPL-1009 / Page 5 of 26
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`

`

`CDLOFMA—STEE;
`
`
`
`Light and colour
`
`The human visual system
`
`Light sources and their characteristics
`
`Colour temperature
`
`Standard illuminants
`
`Classification of colour
`
`How we see colour
`
`Summary
`
`Projects
`
`Film design
`
`Choosing films
`
`Understanding technical descriptions
`
`Film MTF
`
`Characteristic curves
`
`Spectral sensitivity
`
`Reciprocity failure
`
`Product coding
`
`Special materials
`
`Summary
`
`Projects
`
`An introduction to image sensors
`
`Alternative sensor technologies
`
`Image artefacts associated with sensors
`
`Summary
`
`Projects
`
`
`
`APPL-1009 / Page 6 of 26
`
`APPL-1009 / Page 6 of 26
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`

`

`
`
`
`Size of light sources
`
`Direction and angle of light
`
`Distribution of light
`
`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 changes after film processing
`
`Controls during enlarging
`
`Summary
`
`Projects
`
`129
`
`132
`
`133
`
`134
`
`137
`
`139
`
`140
`
`142
`
`144
`
`154
`
`155
`
`178
`
`158
`
`159
`
`183
`
`185
`
`171
`
`173
`
`174
`
`178
`
`177
`
`APPL-1009 / Page 7 of 26
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`APPL-1009 / Page 7 of 26
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`

`

`
`
`Sport and action
`
`Photo—journalism/documentary
`
`Portraiture
`
`Weddings
`
`Landscapes
`
`Architecture
`
`Built studio sets
`
`Studio still-Iifes
`
`Natural history
`
`Aerial subjects
`
`Night skies
`
`Summary
`
`Projects
`
`’l C) 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
`
`APPL-1009 / Page 8 of 26
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`

`

`
`
`i
`
`What is 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
`
`301
`
`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
`24’I
`248
`247
`249
`258
`284
`288
`
`287
`272
`275
`279
`280
`284
`285
`288
`289
`292
`293
`298
`295
`295
`298
`299
`
`APPL-1009 / Page 9 of 26
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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 photographs for 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
`
`385
`
`389
`
`APPL-1009 / Page 10 of 26
`
`APPL-1009 / Page 10 of 26
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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 conversion filter chart
`Appendix [3: Ring around chart
`
`‘
`
`i
`
`Glossary
`
`Index
`
`370
`372
`372
`377
`377
`378
`379
`
`380
`
`370
`
`407
`
`APPL-1009 / Page 11 of 26
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`APPL-1009 / Page 11 of 26
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`

`

`
`
`loading film. Fitting a hood of correct diameter will reduce the risk of something getting in front
`of the lens.
`
`Remember the value of having an instant«picture back, to allow you to confirm visually that
`lens and body are working correctly e plus checking lighting, exposure and composition — at any
`time during a shoot. Some professional photographers habitually expose one instant picture at
`the beginning and another at the end of every assignment, as insurance. It is also a good idea to
`carry another complete camera (a 35 mm SLR, for example) as emergency back—up.
`
`The digital revolution
`
`he first patents for devices capturing images electronically were filed 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; however it was built to test
`the feasibility of digital capture using solid state sensors, rather than as a camera for manufacture
`[due to it’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. The birth of digital
`still cameras as we know them today happened in 1988, when Fuji showcased their camera, the
`DS—1P, at Photokina. Early digital formats could not compete with their film equivalents in terms
`of cost or quality; digital cameras as a practical option for consumers were not really available
`until the mid«1990s Since then the digital market and technologies have grown exponentially.
`The move to digital imaging by many photographers has involved a preceding step via
`’hybrid’ imaging — that is, capture on film 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 has finally arrived. For example, most households in Britain now own at
`least one computer and the majority of new mobile phones have a built—in digital camera. The
`digital camera market has therefore been advanced by the consumer market and of course the
`widespread use of imaging on the Internet.
`
`Immediate results and the ability to easily manipulate, store and transmit images have
`become a priority in many disciplines, with some sacrifice in the quality that we expect in our
`images. In the professional market there have also been compromises between versatility of
`systems and image quality, but progress towards the uptake of entirely digital systems has been
`somewhat slower. In some types of photography image quality is still more important than
`speedy processing and the lack of equipment available in larger formats has meant that film—
`based systems are still common. Sports photography and photojournalism, however, have
`embraced a predominantly digital workflow from capture to output.
`
`Instead of exposing onto silver halide coated film, currently the majority of digital cameras contain
`one of two types of light sensitive array, either a charge—coupled device, known as a CCD, which
`is common in earlier digital cameras, or fast overtaking it, the complementary metal«oxide
`semiconductor or CMOS image sensor. The sensor is in the same position as the film in an analogue
`camera. Many of the key external features of digital and film cameras are similar, but digital cameras
`have a whole other layer of complexity in terms of user controls in the camera software.
`
`APPL-1009 / Page 12 of 26
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`APPL-1009 / Page 12 of 26
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`

`

`
`
`
`
`Both type
`
`s 0f digital image sensor are based on the same material, silicon, which when
`amounts of other elements, can be made sensitive to light. When exposed to
`‘doped’ with small
`light
`it produces a small amount of electrical charge proportional to the amount of light falling
`on it which is stored, transported off the sensor, converted into a stream of binary digits (1’s or
`0'5 hence the name ’digital imaging’), and written into a digital image file. The process is a
`complex one, and the structure and operation of the sensor is covered in more detail in Chapter 6.
`There are many fundamental differences between film—based and digital imaging, not least that
`where a frame of film both captures and stores the image, and is therefore not reusable, a digital
`sensor captures the image, but it is then transported away and stored as an image ’file'
`Somewhere off the Chip. Theoretically, if an image file 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.
`
`Sampled images
`Another key difference between digital and analogue imaging is the fact that the digital image is
`cap
`ruled across a regular grid of pixels (Picture Elements]. Each pixel is an individual image—
`sensing element, which produces
`a response based on the average
`amount of light falling on it.
`Where film ‘grains’ are distributed
`randomly through a film emulsion
`and overlap each other to create
`
`~
`/ T
`_
`f‘
`
`
`
`L
`
`*
`
` ’
`
`,
`
`,
`
`7
`
`.-
`
`i
`
`‘,
`L
`
`i
`
`H
`
`‘
`
`'
`J»
`
`_
`
`77
`
`,
`
`7' i
`
`i
`
`,
`L
`
`
`V
`
`I
`
`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
`
`process of allocating a continuous
`input range of tone and colour to
`a discrete output range which
`changes in steps, is known as
`quantization (see Figure 2.12). The
`whole pixel will be the same
`colour, regardless of the fact that
`the light falling on it in the
`
`Figure 212 Sampling and quantization in a digital image: (a) The image is
`spatially sampled into a grid of discrete pixels; (b) The continuous colour range from
`the original scene is quantized into a limited set of discrete levels, based on the bit
`depth of the image.
`across the pixel areal
`
`
`original scene may have varied
`
`APPL-1009 / Page 13 of 26
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`APPL-1009 / Page 13 of 26
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`

`

`colour values. The stepped changes in colour values and the non—overlapping nature of the pixels
`are limiting factors in the quality and resolution of a digital image. The spatial sampling rate is
`determined by the physical dimensions of the sensor. The quantization levels depend upon the
`sensitivity of the sensor, analogue to digital conversion, image processing in the capture device
`and ultimately on the output file format.
`
`
`
`Resolution is the capability of an imaging system to distinguish between two adjacent points in
`an image and is a measure of the detail—recording ability of a system. It defines how sharp your
`images will appear and what level of fine detail will be represented. In any imaging system this is
`affected by every component through which light passes; in a film«based system the lens and the
`film will be the key factors, but anything placed over the lens or sensor, such as a filter, may also
`afgect it. It is usually the resolution of the image sensor that is the ultimate limiting factor, which is
`why film grain is important, although a poor quality lens, as any photographer knows, is a
`primary cause ofloss of sharpness. There are a number of measures of resolution, but two
`commonly used and covered in more detail in the chapters on lenses and film are resolving power
`and Modulation Transfer Function (MTF).
`
` A digital image is therefore ’sampled’ both across its physical dimensions and in terms of its
`
`Where resolution in traditional film—based imaging is well—defined, the different ways in
`which the term is used and its 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
`means at 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 number of pixels.
`The level of detail that is represented will depend upon how this number of pixels are captured
`or viewed. Therefore, image resolution is often quoted in pixel numbers, calculated by number of
`rows X number of columns. It may be referred 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 monitor resolution, for example, may be quoted in terms of numbers of
`pixels per inch [ppi) and printers are often specified in terms of dots per inch (dpi). The
`combinations of these different resolutions in the output image determine the final image quality
`and also output image size. These relationships are examined in more detail in the chapter on
`digital imaging systems. When quoted by manufacturers of these devices, they will usually quote
`the upper limit for that device, although it will be possible to capture and output images at a
`range of resolutions below this.
`
`A clever trick that manufacturers often use to enhance the apparent characteristics 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 number of individual elements and
`their spacing; however it is possible to rescale an image by interpolating values between the
`actual values, in effect creating false pixels. The visual effects of this are a slight blurring of
`the image, because the interpolation process averages adjacent pixels values to create the
`new pixels.
`
`APPL-1009 / Page 14 of 26
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`APPL-1009 / Page 14 of 26
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`

`

`In cameras too, the effective resolution may be quoted, although manufacturers may not
`identify it 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
`each pixel in 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 FoveonTM chip, has been
`developed, which captures colour at different depths in the sensor and therefore captures all
`GB values at every pixel. This sensor, however, is only available in a few cameras
`three R
`1y on the market, so for the majority, effective resolution still applies.
`current
`
`
`
`How many pixels?
`When buying a digital camera, resolution is a primary consideration, and a key factor in image
`quality, however the previous discussion indicates the confusion around the subject. The highest
`number of megapixels does not necessarily represent the highest quality or automatically mean
`that the largest level of detail will be reproduced. Other factors are involved as well.
`The pixel pitch, which is the centre—to—centre distance between pixels and relates to the
`overall pixel size, is important in determining the maximum level of 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 between imaging areas. Also, the pixel shape; whether there are
`microlenses above each pixel to focus and maximize the light captured; even the interpolation
`algorithms used in calculating missing colour values, which vary between manufacturers, these
`will have an effect on final image resolution. These factors combine to influence the shape of the
`sensor’s MTF and it 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 overall size of the imaging area on the sensor.
`What the 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 number of
`megapixels. Make informed decisions instead, based on results from technical reviews and from
`your own observations through testing out different camera models. You need to decide
`beforehand how you want to use the camera, for what type of subjects, what type of
`photography and what type of output.
`Bearing all 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 those for screen images. Although it 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 image size in terms of output resolution and dimensions, state a
`required file 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 influence on file size.
`Figure 2.13 provides some examples for printed output.
`
`
`
`APPL-1009 / Page 15 of 26
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`APPL-1009 / Page 15 of 26
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`

`

`
`
`INPUT: CMOS or CCD image sensor
`
`OUTPUT: 8 bits per channel RGB images
`printed at 300 dpi
`
`Megapixels
`
`Sensor resolution
`Pixels
`
`Sensor size
`mm
`
`File size
`MB
`
`Output print size
`inches
`
`16.6
`12.7
`10.1
`8.2
`7.1
`
`w
`4992
`4368
`3888
`3504
`3072
`
`h
`3328
`2912
`2592
`2336
`2304
`
`w
`36
`35.8
`22.2
`22.5
`5.7
`
`h
`24
`23.9
`14.8
`15
`4.3
`
`47.5
`36.4
`28.8
`23.4
`20.3
`
`w
`16.6
`14.6
`13.0
`11.7
`10.2
`
`Sensor resolution, dimensions, file size and printed output.
`
`Digital image capture is a complex process. The signal from the sensor undergoes a number of
`processes before it is finally written to an image file. The processes are carried out either on the
`sensor itself, in the camera’s built—in firmware or via camera software, in response to user
`settings. They are designed to optimize the final image according to the imaging conditions,
`camera and sensor characteristics and output required by the user. The actual processes and the
`way they are implemented will vary widely from camera to camera. Some are common to most
`digital cameras however. They will be covered in more detail in other chapters, but are
`summarized below. They include:
`
`Signal amplification: This may be applied to the signal before or after analogue—to—digital conversion; this is a
`result of auto exposure setting within the camera and ensures that the sensor uses its full dynamic range. In
`effect the contrast of the sensor is corrected for the particular lighting conditions.
`Ana/ogue-to—digital conversion: The process of sampling and converting analogue voltages into 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 image processing techniques are used to remove different
`types of noise. Noise is enhanced if the camera gets hot (the sensor is sometimes cooled to reduce the noise
`levels), also if long exposures or high lSO settings are used,
`Unsharp mask filtering: Used to sharpen edges and counteract blurring caused by interpolation.
`Colour interpolation (demosa/cing): This is the process of calculating missing colour values from adjacent colour—
`filtered pixels.
`
`These are sensor specific, in—built and not user controlled. Additionally, settings by the user will
`implement processes controlling:
`
`White balance: The image colours (the gamut) are shifted to correct for the white of the illuminant and ensure
`that neutrals remain neutral. White point setting may be via a list 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 of selecting film for a particular colour temperature and using colour—balancing or colour-
`correction filters.
`
`lSO speed: The sensitivity of the sensor is set by amplifying the signal to produce a required range of output
`values under particular exposure conditions. Again in film cameras, this would be achieved by changing to a film
`
`APPL-1009 / Page 16 of 26
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`APPL-1009 / Page 16 of 26
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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 0f the sensor however is usually TOO—200. Anything above this is a result of
`amplification. Amplifying the signal also amplifies the noise levels and this may show up as coloured patterns in
`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 lens as for a 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 image in 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 when highlight 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 1 I.
`Image resolution: Many cameras, will allow a number of resolution settings, lower than the native resolution of
`the camera to save on file size. These lower resolutions will be achieved by down—sampling, either dropping pixel
`values completely if the image is being downsampled by a factor of 2, or by interpolating values from the
`existing sensor values.
`Capture into a standard co/our space: With the necessary adoption of colour-managed workflow, a number of
`standard colour spaces have emerged. Capturing into a standard colour space means that the image gamut has
`the best chance of being reproduced accurately throughout the imaging chain (see Chapter If for further details).
`The two most commonly used standard colour spaces in digital cameras are sRGB and Adobe R68 (1998). sRGB is
`Optimized for images to be viewed on screen. The slightly larger gamut of Adobe RGB encompassed the range of
`colours reproduced by most printers and is therefore seen as more suitable for images that are to be printed.
`Fi/e quality (if image is to be compressed) and file format: I\/Iost cameras will offer a range of different output file
`formats. The most common ones in digital cameras are JPEG, TIFF and RAW formats. The merits of these different
`formats are discussed in detail in Chapter I I. 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 the loss, file size and resulting artifacts.
`TIFF and RAW are uncompressed and therefore file 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 above is
`performed by the user in separate software after the image has been downloaded from the camera.
`
`.
`
`.
`
`This short summary highlights some of the differences between using film and working
`digitally. The immediacy of results from digital cameras is somewhat counterbalanced by the
`number of settings required by the user before image capture. However it also highlights the
`high degree of control that you have. Many of the adjustments that would have to be performed
`Optically with a film-based system, or by changing film stock, may be achieved by the flick of a
`switch or the press of a button.
`
`Digital sensor- sizes
`One of the initial problems in producing digital cameras with comparable image quality to film
`was the difficulty and expense in manufacturing CCDs of equivalent areas. Many digital cameras
`have sensors which are significantly smaller than 35 mm format. The sizes 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 16 mm. Examples of the actual dimensions of some image sensors are
`shown in Figure 2.14, compared to typical film formats.
`
`
`APPL-1009 / Page 17 of 26
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`APPL-1009 / Page 17 of 26
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`

`

`Film
`35 mm
`120 mm
`
`Large format
`
`Horizontal Vertical Diagonal Aspect SensorType
`Ratio
`(mm)
`(mm)
`(mm)
`
`36.0
`60.0
`
`24.0
`60.0
`
`43.3
`84.9
`
`120.0
`
`101.6
`
`162.6
`
`3:2
`1:1
`
`5:4
`
`4:3
`4:3
`4:3
`4:3
`4:3
`4:3
`3:2
`3:2
`
`3:2
`1:1
`4:3
`4:3
`4:3
`4:3
`
`Film
`Film
`
`Film
`
`CMOS
`COD/CMOS
`COD/CMOS
`CCD/CMOS
`COD/CMOS
`COD/CMOS
`CMOS
`CCD
`
`CMOS
`Full frame CCD
`Full frame CCD
`Trilinear array CCD
`Trilinear array CCD
`Trilinear array CCD
`
`1.9
`4.0
`4.8
`5.3
`6.6
`9.6
`14.8
`15.7
`
`24.0
`36.9
`36.0
`36.9
`72.0
`84.0
`
`3.2
`6.7
`8.0
`8.9
`11.0
`16.0
`26.7
`28.4
`
`43.3
`52.2
`60.0
`61.0
`120.0
`130.6
`
` Sensor/format
`
`Digital sensors — consumer market
`1/5
`2.6
`1/2.7
`5.4
`1/2
`6.4
`1/1.8
`7.2
`2/3
`8.8
`12.8
`22.2
`23.7
`
`.8*
`1.8*
`
`1 1
`
`Digital sensors — professional market
`Full frame 35 mm
`36.0
`36.9
`Medium/large format back
`48.0
`Medium/large format back
`49.0
`Medium/large format back
`96.0
`Large format back
`100.0
`Large format back
`
`* There are a variety of different sensors labelled 1.8 and sizes vary slightly between manufacturers
`
`Dimensions of typical film formats and digital image sensors.
`
`The small sensor sizes mean that in most digital cameras the focal lengths of lenses are
`significantly shorter than in film—based systems. This has a number of implications. First of all, it
`means that in the compact market, it has been possible to make much smaller camera bodies,
`and this is the reason that miniature cameras have proliferated (it has also made the tiny
`cameras used in mobile phones a possibility, see below). As for film camera formats, a shorter
`focal length means greater depth of field. The result of this is that using a shallow depth of field
`for selective focus on a subject is much more difficult in digital photography, because more often
`than not everything in frame appears sharp. This is one of the reasons that professionals often
`prefer a full—frame sensor of the same size as the equivalent film format, because in this case the
`lens focal lengths and depth of field will be the same as for film.
`
`A further implication of the smaller sensors is that lens of focal lengths designed for film
`formats will produce a smaller angle of view when placed on a digital camera with a smaller
`sensor. This means that standard focal length lenses effectively become telephoto lenses (see
`Figure 2.15). The problem affects small-format SLRs, where lenses from the equivalent film
`format might be used, and also the larger formats when using digital backs with a smaller
`imaging area than the associated film back. It can also cause confusion when comparing the
`zoom lenses of two cameras with different—sized sensors. Effective focal length is sometimes
`quoted instead. This expresses the focal length as the same as a focal length of a lens on a film
`camera, usually 35 mm, based on an equivalent angle of view.
`
`APPL-1009 / Page 18 of 26
`
`APPL-1009 / Page 18 of 26
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`

`

`Projected image is circular and
`covers the diagonal of the format
`t
`
`
`
`Film: 24 X 36 mm
`image area using a
`50 mm focal length
`
`lens with 135 film
`
`14 X 22 mm 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 Change in angle of view as a result of smaller sensor size and focal length. Manufacturers often quote 'effective focal length'
`for digital lenses, which relates the field of view of the lens to that provided by the focal length of the lens in the related film format.
`
`Digital camera equipment
`
`igital camera equipment is less easily classified by image
`format than film simply because of the huge variation in
`sensor size. Cameras can, however, be put into broad
`
`categories based upon the mar