FOCUSING the VIEW CAMERA A Scientific Way to focus the View Camera and Estimate Depth of Field J by Harold M. Merklinger FOCUSING the VIEW CAMERA A Scientific Way to focus the View Camera and Estimate Depth of Field by Harold M. Merklinger Published by the author This version exists in electronic (PDF) format only. ii Published by the author: Harold M. Merklinger P. O. Box 494 Dartmouth, Nova Scotia Canada, B2Y 3Y8. v. 1.0 1 March 1993. 2nd Printing 29 March 1996. 3rd Printing 27 August 1998. Internet Edition (v. 1.6.1) 8 Jan 2007 ISBN 0-9695025-2-4 © All rights reserved. No part of this book may be reproduced or translated without the express written permission of the author. ‘Printed’ in electronic format, by the author, using Adobe Acrobat. Dedicated to view camera users everywhere. FOCUSING THE VIEW CAMERA iii CONTENTS Page Preface ...............................................................................................................iv CHAPTER 1: Introduction ............................................................................1 CHAPTER 2: Getting Started .......................................................................3 CHAPTER 3: Definitions .............................................................................11 The Lens ...................................................................................................11 The Film and the Image Space .................................................................19 The Plane of Sharp Focus and the Object Space .....................................23 Other Terms and Distances ......................................................................27 CHAPTER 4: View Camera Optical Principles.........................................29 Tilt and Swing ..........................................................................................36 Discussion ................................................................................................37 CHAPTER 5: Perspective and Distortion ..................................................39 CHAPTER 6: Depth of Field .......................................................................49 Image-Based Depth of Field ....................................................................49 Object-Based Depth of Field ...................................................................53 Discussion ................................................................................................55 CHAPTER 7: A Simpler Method ................................................................57 CHAPTER 8: An Example...........................................................................61 CHAPTER 9: Tutorial..................................................................................67 Considerations ..........................................................................................67 A Solution ................................................................................................71 Additional Comments ..............................................................................74 Other Ways ..............................................................................................75 CHAPTER 10: Summary ...............................................................................79 Main Message ..........................................................................................79 Table of Hyperfocal Distances .................................................................80 Bibliography ............................................................................................82 CHAPTER 11: Tables ....................................................................................85 Index to Tables .........................................................................................87 Effective focal length ...............................................................................88 iv Merklinger: FOCUSING THE VIEW CAMERA CHAPTER 11: Tables (continued) Hinge line tilt ...........................................................................................91 Effective tilt for both swing and tilt .........................................................90 Lens tilt angle for given focal length f and distance J .............................93 Distance J for given tilt ...........................................................................96 Back focus distance A ............................................................................100 Depth of Field ........................................................................................105 Lens-to plane of sharp focus distance D ................................................128 Hyperfocal Distance, H ..........................................................................134 Index to Tables (repeated) .....................................................................130 Blank Charts ..................................................................................................131 Inserts provided with printed version .........................................................133 The National Aviation Museum, Ottawa In this photograph, the plane of sharp focus was set to emerge from the ground at the lower edge of the picture, and rise slowly to pass half-way through the hangar. PREFACE v Preface I have been active in photography since about 1950, when I was eight or nine years old. Over the past 56 years most of my photography has been done with 35 mm cameras. I have always wanted to pack lots of detail into my pictures, and that yearning has caused me to investigate medium and larger format cameras from time to time. I even owned an 8ϫ10 camera back in the early 1960SÑwhen I couldnÕt afford to run it. For the most part, however, I have been able to achieve what I intended with 35 mm cameras and slow film, sometimes resorting to 645 or 6ϫ6 format. My previous book, The INs and OUTs of FOCUS, explains how to achieve highly detailed images with almost any format. From time to time, the Graphic Century or Super Technika 23 has been called into action, primarily for the rising front feature. These cameras have a tilting front standard, but it only tips backwards. To achieve a forward lens tilt, one must either suspend the camera upside down, or drop the bed. The inconvenience of that design ensured that I remained largely ignorant of view camera principles for most of my photographic life. Although I knew vaguely of the Scheimpflug Principle, and even tried to use it on occasion, I never really applied it wellÑor trusted it, for that matter. Was this a reliable photographic tool? Or was this another example of rules like the depth of field Òone-third ruleÓ which offers useful advice but lacks rigor. One of the very first people to buy a copy of The INs and OUTs of FOCUS was Raymond Clark, President of ImageQuest Corporation in Colorado. Within a couple of weeks I received a letter from him asking how things work for view cameras when the lens is tilted. I had never attempted to work out the optics of tilted planes before, but here was a challenge. Relatively quickly, I was able to satisfy myself that the Scheimpflug Principle was exactÑfor thin, rectilinear, flat field lenses. If I could convince myself what the standard ÔcorrectÕ perspective was, I would also be able to describe depth of field for tilted planes. The depth of field went to zero at a strange point in space. One often sees drawings showing the depth of field vanishing where the lens plane, film plane and plane of sharp focus intersect. But in my solution the vanishing point was somewhere else. The correspondence between Raymond Clark and myself continued, and offered the encouragement I needed to continue the investigation. Eventually, I realized that there was not just one rule at play, but two. The Scheimpflug Principle contains only half of the needed information. A second rule contains the other half. This ruleÑwhich I have called the hinge rule in this bookÑ is so simple, it seems unlikely to me that its photographic significance has not vi Merklinger: FOCUSING THE VIEW CAMERA been documented in photography texts. Yes, Theodore Scheimpflug did know about itÑit is noted in his British PatentÑbut it was apparently of less importance to his problem (making maps from oblique aerial photographs) than the rule that bears his name. Let me be the first to point out that I am not an experienced view camera user. Yes, I have used semi-view cameras for decades, but finding the right amount of lens tilt was more effort than warranted for my purposes. Since uncovering the second rule, however, I have found focusing the view camera to be less than twice the work required to focus an ordinary camera. Applying the hinge rule removes all necessity for seemingly endless cycles of tilt and back-focus adjustment. The hinge rule is more useful than the Scheimpflug Rule. The few photographs accompanying this book were taken with an old Burke and James wooden 5ϫ7 view camera equipped with a C. P. Goerz American Optical Co. 9.5 inch Gold Ring Dagor, and with Kodak Tri-X film (not T-Max). All of them were taken at f/22: an aperture 11 millimeters in diameter. I will not claim that these are great works of art. Nor do they constitute particularly tough tests for a view camera. They are, however, relatively typical of the photographs I like to take. What impresses me most about them is how quickly they were taken. On one outing, without even trying to work quickly, I realized in retrospect that I had taken four photographsÑall with different