Juergen Gulbins - Photographic Multishot Techniques

High Dynamic Range, Super-Resolution,
Extended Depth of Field, Stitching

Juergen and Rainer Gulbins

Rainer Gulbins,

Editor: Gerhard Rossbach
Layout and Type: Juergen Gulbins
Translator: Gerhard Schneibel
Copyeditor: Jeremy Cloot
Cover Design: Helmut Kraus, www.exclam.de
Cover Photo: Helmut Kraus
Printer: Courier Corporation
Printed in the USA

ISBN-13: 978-1-933952-38-3
1st Edition (2nd Printing, April 2010) 2009 by Juergen Gulbins and Rainer Gulbins

Rocky Nook Inc.
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Santa Barbara, CA 93101
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First published under the title
Multoshot-Techniken in der digitalen Fotografie
Copyright 2008 dpunkt.verlag GmbH, Heidelberg, Germany

Library of Congress Cataloging-in-Publication Data
Gulbins, Jrgen.
[Multishot-Techniken in der digitalen Fotografie. English]
Photographic multishot techniques : super-resolution, extended depth of field, stitching, high dynamic
range imaging, and other image enhancement techniques / Juergen and Rainer Gulbins. 1st ed.
p. cm.
Includes bibliographical references and index.
ISBN 978-1-933952-38-3 (alk. paper)
1. High dynamic range imaging. 2. Imaging systemsImage quality. I. Gulbins, Rainer. II. Title.
TR594.G85 2009
771dc22
2008053325

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This book is printed on acid-free paper.

Digital cameras first became widely available in 2002. Since then, technical advances have not only rapidly increased image sensor resolution, but have also brought great improvements to camera technology in general. The problem of image noise has been addressed, dynamic range has been increased, and cameras are constantly being equipped with ever-faster image processors. Faster processors have simplified the use of bracketing techniques, which allow the photographer to automatically shoot sequences of shots with varied exposure settings.

Parallel to these developments, image processing software has also been improving rapidly. RAW conversion is now a simple process, and can be combined with many automatic and manual image correction functions. Modern digital lens correction functions also achieve high-quality results. Combined with appropriate shooting techniques, such technical advancements make previously unimaginable image processing possible. One of the most powerful new options available to the digital photographer is the ability to create a high-quality image by combining multiple shots. This book addresses the use of the following multishot techniques:

1. Super-Resolution, used to increase overall image resolution

2. Focus Stacking, used to increase depth of field

3. Stitching, used to create panoramic photos

4. HDRI Techniques, used to increase the dynamic range of an image

5. Plus other techniques for reducing image noise, and the general optimization of the multishot images you have generated

This book is intended as an introduction to these techniques and demonstrates how to apply them practically using widely available applications.

We will keep theory to a minimum throughout this book, although the technical aspects of the processes described are sometimes very complex. We will also limit the number of software applications we demonstrate. Introducing all the applications available on todays market would not benefit most users, and new programs and program functions are constantly being introduced anyway.

The basic approach to multishot techniques (which many professionals have long used in simplified form) is as follows:

Once weve found the right angle, lighting and composition for a shot, we make several exposures of the same scene, each with different exposure settings, and hopefully in sharp focus. Taking multiple pictures doesnt cost the digital photographer any extra money. When shooting such bracketed sequences, the aperture should remain the same while the shutter speed is increased or decreased at set intervals.

You can then simply view the whole sequence at home and choose the best-exposed shot for further processing. At this point, were often ready to move directly on to the image optimization stage.

Figure 1-1: A series of three images taken at Monument Valley in the United States. The exposures were varied using different shutter speeds. We think the picture in the middle turned out the best, so we used this one for processing and optimization.

However, the applications described in this book offer a number of other options for processing your image sequences, including:

1. If image resolution isnt sufficient, for example, for large-format printing, we can use the techniques described in to combine multiple images to make a single image with increased resolution. To achieve this, we need at least four images the more the better.

2. If poor light forces us to shoot at high ISO speeds, we can combine images to reduce noise. This can be achieved using PhotoAcute (described in .

Figure 1-2: Here we see a scaled-down version of the original picture along with two detail images. The center detail was taken from the original image, and the one to the right was taken from a super-resolution image created using PhotoAcute.

3. If the exposure range of an image isnt broad enough to capture the dynamic range of a high-contrast scene, its possible to increase the dynamic range of your best image by augmenting it with data from the other images in the series. This can be achieved using the PhotoAcute method described in , or using a simple layer mask technique in Photoshop. HDRI stands for High Dynamic Range Imaging.

Figure 1-3: Above are three shots of an old-fashioned carpenters workshop. They were taken using different exposure settings. Because the light outside the windows is drastically different than the light inside the building, its impossible for a camera to capture the entire dynamic range of the scene and to properly expose both sections of the image. The image on the left shows a combined image created using HDRI. The image was also post-processed to correct perspective distortion.