© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. "Digital Media Primer" Yue-Ling Wong, Copyright (c)2016 by Pearson Education, Inc. All rights reserved. © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

Chapter 3 Capturing and Editing Digital Images Part 1 Digitizing Images by Scanning © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

In this lecture, you will find answers to these questions What is dpi? What is the best scanning resolution? What is involved to capture a digital image by scanning? © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Types of Scanners Flatbed Sheet-fed Handheld Drum © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Scanner Resolution Optical resolution Enhanced resolution Reported in dpi (dots per inch) © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

To see what "dots" in dpi stands for, let's look at how scanners work. © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. How Scanners Work A flatbed scanner has a moving scan head. A scan head contains an array (or a row) of light sensors. The scan head moves across the scanner bed during scanning. Its movement is controlled by a stepper motor. © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Dot Each sensor will produce a sample (a color value) corresponding to a position of the picture being scanned. A sensor: a dot Each sample (color value) results in a pixel in the scanned image. © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Dot vs. Pixel Generally speaking, a dot (sensor) produces a sample (pixel). But a dot is not a pixel. © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. A scan head only have one row of sensor. So how can it produce color values for a whole picture? © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Here is how Get a row of color values Move the scan head forward a little bit Get another row of color values . © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Sampling Recall sampling and sampling rate in the sampling step in digitization. Sampling rate in the x-direction of a picture: The number of sensors available in the row Sampling rate in the y-direction of a picture: The discrete stepwise movement of the scan head © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

Determining Scanning Resolution How the scanned image will be used: Print physical dimensions of the image requirement of the printing device (e.g. printing resolution) Web or on-screen display pixel dimensions of the image © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

Determining Scanning Resolution Basic steps: Determine the pixel dimensions of the final image Determine the scanning resolution (pixel dimensions from step 1) / (physical dimensions of your picture) © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

Determining Scanning Resolution for Web or On-screen Display Example Suppose: the monitor resolution of your target audience is 1600  1050 pixels you want your image to appear about ½ the width and height of the screen your original picture is 5"  4" Step 1. The pixel dimensions of your final image should be 800  525 pixels. Step 2. Scanning resolution based on the width = 800 pixels / 5"  1 dot/pixel = 160 dpi Scanning resolution based on the height = 525 pixels / 4 "  1 dot/pixel = 131 dpi We will pick the highest dpi of the two, i.e., 160 dpi With 160 dpi, your final image will have the pixel dimensions: 5"  160 dpi  1 pixel/dot = 800 pixels 4"  160 dpi  1 pixel/dot = 640 pixels If you want exactly 800  525 pixels, you will need to crop the final image. © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

Determining Scanning Resolution for Print Example Suppose: your original picture is 5"  4" you want to scan the picture to print as 13"  10" at 300 ppi Step 1. The pixel dimensions of your final image should be: 13"  300 ppi = 3900 pixels 10"  300 ppi = 3000 pixels Step 2. Scanning resolution based on the width = 3900 pixels / 5"  1 dot/pixel = 780 dpi Scanning resolution based on the height = 3000 pixels / 4 "  1 dot/pixel = 750 dpi We will pick the highest dpi of the two, i.e., 780 dpi. You may also round it up to 800 dpi. With 780 dpi, your final image will have the pixel dimensions: 5"  780 dpi  1 pixel/dot = 3900 pixels 4"  780 dpi  1 pixel/dot = 3120 pixels © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

Determining Scanning Resolution for Print Example The final image 3900  3120 pixels will be printed in these physical dimensions: 3900 pixels / 300 ppi = 13" 3120 pixels / 300 ppi = 10.4" If you want exactly 13"  10", you will need to crop the final image. © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

Tonal Adjustments During Scanning Maximize tonal range during scanning Any tonal ranges cropped off during scanning will not be recovered after scanning Tonal range adjustment and histograms will be explained later in the chapter. © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

Tonal Range Maximized During Scanning histogram use maximized tonal range © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

Use Narrow Tonal Range During Scanning histogram use narrow tonal range Missing very dark and very bright tones. Looks dull and low in contrast. © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

Crop off Highlights During Scanning histogram crop off highlights The brightest areas all become white. © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Also see the interactive tutorial: Tonal Adjustments During Scanning An interactive tutorial that explains and demonstrates why tonal optimization is necessary during scanning. © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Review Questions Note to instructor: Depending on your preference, you may want to go over the review questions at the end of this lecture as an instant review or at the beginning of next lecture to refresh students' memory of this lecture. © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Review Question True/False: The optimization of tonal adjustment at the time of capturing images--scanning or digital photography--does not matter because you can always extend the tonal range of the image to any extent afterwards in image editing applications, such as Photoshop. False © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Review Question Suppose that you scan a 2"  1" picture in at a resolution of 300 dpi. What are the pixel dimensions of the scanned image? ___ pixels  ___ pixels (i) 600  300 because 2"  300 dpi  1 pixel/dot = 600 pixels, and 1"  300 dpi  1 pixel/dot = 300 pixels © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Review Question Suppose that you scan a 2"  1" picture in at a resolution of 300 dpi. What are the pixel dimensions of the scanned image? ___ pixels  ___ pixels What will the physical dimensions of the image be if you print it at 300 ppi? ___" ___" (i) 600  300 because 2"  300 dpi  1 pixel/dot = 600 pixels, and 1"  300 dpi  1 pixel/dot = 300 pixels (ii) 2" x 1" because 600 pixels / 300 ppi = 2", and 300 pixels / 300 ppi = 1" © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Review Question Suppose that you scan a 2"  1" picture in at a resolution of 300 dpi. What are the pixel dimensions of the scanned image? ___ pixels  ___ pixels What will the physical dimensions of the image be if you print it at 300 ppi? ___" ___" What will the physical dimensions of the image be if you print it at 600 ppi? (i) 600  300 because 2"  300 dpi  1 pixel/dot = 600 pixels, and 1"  300 dpi  1 pixel/dot = 300 pixels (ii) 2" x 1" because 600 pixels / 300 ppi = 2", and 300 pixels / 300 ppi = 1" (iii) 1" x 0.5" because 600 pixels / 600 ppi = 1", and 300 pixels / 600 ppi = 0.5" © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Review Question Suppose that you scan a 2"  1" picture in at a resolution of 300 dpi. What are the pixel dimensions of the scanned image? ___ pixels  ___ pixels What will the physical dimensions of the image be if you print it at 300 ppi? ___" ___" What will the physical dimensions of the image be if you print it at 600 ppi? What will the physical dimensions of the image be if you print it at 150 ppi? (i) 600  300 because 2"  300 dpi  1 pixel/dot = 600 pixels, and 1"  300 dpi  1 pixel/dot = 300 pixels (ii) 2" x 1" because 600 pixels / 300 ppi = 2", and 300 pixels / 300 ppi = 1" (iii) 1" x 0.5" because 600 pixels / 600 ppi = 1", and 300 pixels / 600 ppi = 0.5" (iv) 4"  2" because 600 pixels / 150 ppi = 4", and 300 pixels / 150 ppi = 2" © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Review Question Suppose that you scan a 2"  1" picture in at a resolution of 300 dpi. What are the pixel dimensions of the scanned image? ___ pixels  ___ pixels What will the physical dimensions of the image be if you print it at 300 ppi? ___" ___" What will the physical dimensions of the image be if you print it at 600 ppi? What will the physical dimensions of the image be if you print it at 150 ppi? True/False: You gain image detail and quality if you print the image at 600 ppi as noted in (iii). (i) 600  300 because 2"  300 dpi  1 pixel/dot = 600 pixels, and 1"  300 dpi  1 pixel/dot = 300 pixels (ii) 2" x 1" because 600 pixels / 300 ppi = 2", and 300 pixels / 300 ppi = 1" (iii) 1" x 0.5" because 600 pixels / 600 ppi = 1", and 300 pixels / 600 ppi = 0.5" (iv) 4"  2" because 600 pixels / 150 ppi = 4", and 300 pixels / 150 ppi = 2" (v) False because it is the same image with the same number of pixels © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

© 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved. Review Question Suppose that you scan a 2"  1" picture in at a resolution of 300 dpi. What are the pixel dimensions of the scanned image? ___ pixels  ___ pixels What will the physical dimensions of the image be if you print it at 300 ppi? ___" ___" What will the physical dimensions of the image be if you print it at 600 ppi? What will the physical dimensions of the image be if you print it at 150 ppi? True/False: You gain image detail and quality if you print the image at 600 ppi as noted in (iii). True/False: You lose image detail and quality if you print the image at 150 ppi as noted in (iv). (i) 600  300 because 2"  300 dpi  1 pixel/dot = 600 pixels, and 1"  300 dpi  1 pixel/dot = 300 pixels (ii) 2" x 1" because 600 pixels / 300 ppi = 2", and 300 pixels / 300 ppi = 1" (iii) 1" x 0.5" because 600 pixels / 600 ppi = 1", and 300 pixels / 600 ppi = 0.5" (iv) 4"  2" because 600 pixels / 150 ppi = 4", and 300 pixels / 150 ppi = 2" (v) False because it is the same image with the same number of pixels (vi) False because it is the same image with the same number of pixels © 2016 Pearson Education, Inc., Hoboken, NJ. All rights reserved.