The Art and Science of Digital Compositing Second Edition PPrelims-p370638.inddrelims-p370638.indd i 33/24/2008/24/2008 88:31:05:31:05 PPMM PPrelims-p370638.inddrelims-p370638.indd iiii 33/24/2008/24/2008 88:31:06:31:06 PPMM The Art and Science of Digital Compositing Techniques for Visual Effects, Animation and Motion Graphics Second Edition Ron Brinkmann PPrelims-p370638.inddrelims-p370638.indd iiiiii 33/24/2008/24/2008 88:31:06:31:06 PPMM Acquisitions Editor: Tiffany Gasbarrini Publishing Services Manager: George Morrison Project Manager: Mónica González de Mendoza Assistant Editor: Matt Cater Cover Design: Joanne Blank Cover Images: See page xii for full credits Morgan Kaufmann Publishers is an imprint of Elsevier 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA This book is printed on acid-free paper. © 2008 Elsevier, Inc. All rights reserved. Designations used by companies to distinguish their products are often claimed as trademarks or registered trademarks. In all instances in which Morgan Kaufmann Publishers is aware of a claim, the product names appear in initial capital or all capital letters. Readers, however, should contact the appropriate companies for more complete information regarding trademarks and registration. 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, scanning, or otherwise—without prior written permission of the publisher. Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone: (ϩ44) 1865 843830, fax: (ϩ44) 1865 853333, E-mail: [email protected]. You may also complete your request online via the Elsevier homepage (http://elsevier.com), by selecting “Support & Contact” then “Copyright and Permission” and then “Obtaining Permissions.” Library of Congress Cataloging-in-Publication Data Brinkmann, Ron. The art and science of digital compositing / Ron Brinkmann. p. cm. Includes bibliographical references and index. ISBN-13: 978-0-12-370638-6 (pbk. : alk. paper) 1. Computer graphics. 2. Image processing—Digital techniques. I. Title. T385.B75 2008 778.5Ј2350285—dc22 2007053015 ISBN: 978-0-12-370638-6 For information on all Morgan Kaufmann publications, visit our Web site at www.mkp.com or www.books.elsevier.com 08 09 10 11 12 13 10 9 8 7 6 5 4 3 2 1 Printed in China PPrelims-p370638.inddrelims-p370638.indd iivv 33/24/2008/24/2008 88:31:11:31:11 PPMM Contents Introduction to the Second Edition ..................................................................................xiii Chapter 1 Introduction to Digital Compositing ............................................................1 Defi nition ....................................................................................................................................2 Historical Perspective ...............................................................................................................3 Terminology ...............................................................................................................................7 Organization of the Book .......................................................................................................11 Chapter 2 Learning to See ...........................................................................................15 Judging Color, Brightness, and Contrast .............................................................................16 Light and Shadow ...................................................................................................................19 The Camera ..............................................................................................................................27 Resolution Limits ...............................................................................................................27 Focus and Depth of Field ...................................................................................................30 Lens Flares and Other Lens Artifacts ................................................................................32 Motion Blur .......................................................................................................................39 Depth, Distance, and Perspective .........................................................................................41 Perspective and the Camera ...............................................................................................42 Depth Cues.........................................................................................................................45 Visual “ Correctness ” ...............................................................................................................51 Chapter 3 The Digital Representation of Visual Information ....................................53 Image Generation ....................................................................................................................53 Pixels, Components, and Channels ......................................................................................55 Spatial Resolution ...................................................................................................................59 Bit Depth ...................................................................................................................................60 Normalized Values..................................................................................................................63 Beyond Black and White ........................................................................................................64 Floating-point and High Dynamic Range Imagery (HDRI) .............................................71 The HSV Color Representation .............................................................................................74 The YUV Color Representation .............................................................................................77 Image Input Devices ...............................................................................................................80 Digital Image File Formats ....................................................................................................81 File Format Features ...............................................................................................................82 Variable Bit Depths ............................................................................................................82 Different Spatial Resolutions .............................................................................................82 Compression .......................................................................................................................82 Comment Information in a Header ....................................................................................82 Additional Image Channels ...............................................................................................82 PPrelims-p370638.inddrelims-p370638.indd v 33/24/2008/24/2008 88:31:11:31:11 PPMM vi Contents Vendor-specifi c File Format Implementations ....................................................................83 Compression ............................................................................................................................83 Run-length Encoding ........................................................................................................83 Lossy Compression .............................................................................................................86 Chroma Subsampling.........................................................................................................87 Image Sequence Compression ............................................................................................90 Choosing a File Format ..........................................................................................................90 Nonlinear Color Encoding .....................................................................................................91 Chapter 4 Basic Image Manipulation .........................................................................93 Terminology .............................................................................................................................94 Color Manipulations ...............................................................................................................97 RGB Multiply ....................................................................................................................97 Add .....................................................................................................................................98 Gamma Correction ...........................................................................................................100 Invert ................................................................................................................................102 Contrast ...........................................................................................................................103 Channel Swapping ...........................................................................................................106 HSV Manipulations ........................................................................................................107 Look-up Table Manipulations ..........................................................................................108