Cover The Textbook of Digital Photography Pixels and Images

1 AA30470C. Cover An Extension to The Textbook of Digital Photography Pixels and Images AA30470C. Dennis P. Curtin http : / / w w w . ShortCourses. c o m For more on Digital Photography , visit . Pixels & Images ShortCourses and PhotoCourse Publishing Programs S. hort Courses, the parent site of , is the leading publisher of Digital Photography books, textbooks, and guides to specific cameras. Be sure to visit the Short Courses bookstore at http://. One of our specialities is high- quality, easy to follow, camera guides so be sure to visit the store to see if there is a guide to your camera.

2 If you find any errors in this book, would like to make suggestions for improvements, or just want to let me know what you think I welcome your feedback, even though I can't always respond person- ally. Contact/Feedback Information 16 Preston Beach Road Marblehead, Massachusetts 01945. E-mail: Copyright Notice Copyright 2007 by Dennis P. Curtin. All rights reserved. Printed in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication, or the resources to which it links, may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher.

3 Web Sites To learn more about Digital Photography visit our two Web sites: Click to view a PDF. document on how copyright law protects photographers and EDUCATORS. other artists. PhotoCourse and Short Courses books are used by hundreds of schools, major camera companies, police and military training programs. If you are an instructor, you should know that special pricing is available for classroom use. Click to view a PDF. For details on using this and other texts in the classroom, please document on how call us at 781-631-8520, Boston Massachusetts USA time.

4 Copyright law protects photographers and other artists. For more on textbooks in Digital Photography , visit AA30470 CIntroduction Introduction J. Emily plays a priest ust because Photography is an art form, it doesn't mean you don't in a Shakespeare have to know some math. When it comes to displaying or printing production at Ft. Sewall. The evening light casts your Images , this section could be titled So You Have to Know Arith- a warm glow on the metic After All. If your camera captures an image that's 3648 x 2736. scene. Pixels in size, what does that mean when you e-mail it, post it to a Web site, or make a print?

5 In this section you find out how to answer these kinds of questions. The calculations we'll be using in this section are nothing more than subtrac- tion, addition, multiplication and division subjects you mastered early in school. However, to make it easier to explore the various relationships being discussed, you can use the Excel worksheet Pixels & Images Calculator . downloadable at the link below or by clicking the Excel button in this section: Click to open the Excel worksheet. The worksheet, named , has been saved in Excel 5 format so that version and all later versions of Excel can read it.

6 For more on Digital Photography , visit . Pixels & Images Part 1. Pixels , Image Sizes and Aspect Ratios Let's start with one surprising fact: A pixel has no size or shape. At the time it's born, it's simply an electrical charge much like the static electricity that builds up on your body as you shuffle across a carpet on a dry day. A pixel is only given size and shape by the device you use to display or print it. Under- standing how Pixels and image sizes relate to one another takes a little effort but you need to bring nothing more to the process than your curiosity and elementary school arithmetic skills.

7 Pixels Tip A pixel begins its life on the camera's image sensor during that flickering The number of moment when the shutter is open. The size of each photosite on the image photosites on an im- sensor can be measured, but the Pixels themselves are just photons, soon age sensor is fixed during the design to be converted into electrical charges, and then into zeros and ones. These and manufacturing numbers, just like any other numbers that run through your head, have no process. In most physical size. cases each photosite captures one pixel in Although the captured Pixels have no physical dimensions, a sensor's size is the image.

8 However, a few companies use specified just like a Digital photo's, except the count is the number of pho- software to inflate tosites that it has on its surface instead of Pixels . In most cases the numbers their Images by add- of photosites and the number of Pixels are roughly the same since each ing Pixels to them, a process driven by the photosite captures one pixel . (see Tip box for more on this.) These sizes are marketing depart- usually specified in one of two ways by the dimensions or by its total num- ment so they can ber. For example, an image can be said to have 4368 2912 Pixels (where claim more Pixels than they actually is pronounced by as in 4368 by 2912), or to contain million Pixels provide.

9 (4368 multiplied by 2912). Since the term megapixel is used to indicate 1. million Pixels , an image with million Pixels can also be referred to as a megapixel image. This image taken in the Mojave Desert is 4368. Pixels wide and 2912. Pixels tall. It's said to be 4368 by 2912. For more on textbooks in Digital Photography , visit Part 1. Pixels , Image Sizes and Aspect Ratios Since Pixels stored in an image file have no physical size or shape, it's not surprising that the number of Pixels doesn't by itself indicate a captured image's sharpness or size.

10 This is because the size of each captured pixel , and the image of which it's a part, is determined by the output device. The device can spread the available Pixels over a small or large area on the screen or printout. If the Pixels in an image are squeezed into a smaller area, the image gets smaller and the perceived sharpness increases (from the same viewing dis- tance). Images on high-resolution screens and printouts look sharper only because the available Pixels are smaller and grouped into a small area not because there are more Pixels . As Pixels are enlarged, an image is spread over a larger area, and its perceived sharpness falls (from the same viewing distance).