Using Adobe Photoshop to enhance the image quality Assistant course web site: http://www.arches.uga.edu/~skwang/edit6170/course.htm
Content Introduction 2 Unit1: Scan images 3 Lesson 1-1: Preparations of scanning images 3 Lesson 1-2: Resolution setting 3 Unit 2: Adjust images 5 Lesson 2-1: adjusting image resolution with Photoshop 5 Lesson 2-2: cropping image 5 Lesson 2-3: transforming image 6 Unit 3: Selection tools and layers 7 Lesson 3-1: using selection tools 7 Lesson 3-2: using layer palette 7 Unit 4: Use Photoshop color adjusting commands 9 Lesson 4-1: adjusting sharpness 9 Lesson 4-2: adjusting level 9 Lesson 4-3: adjusting saturation 10 Unit 5: Use Photoshop layer mode 11 Lesson 5-1 for selecting layer modes 11 Lesson 5-2: adjusting layer modes 11 Unit 6: Export images 12 Lesson 6-1 for exporting with GIF file 12 Lesson 6-2: exporting with JPEG file 12 Can you do it? 14 Using Adobe Photoshop to enhance the image quality 1
Introduction Course goal Understand the basic computer graphic concepts and use image process software to enhance the quality of images. Objectives You should be able to do the following after instruction: Given raw images, you will be able to use Adobe Photoshop to: Scan the pictures into digital files Adjust the appropriate resolution of the image for delivering into web Adjust the level, saturation of the image to enhance the quality Make the decision of applying Photoshop commands to repair the overexposing or underexposing pictures. Using Adobe Photoshop to enhance the image quality 2
Unit 1: Scan images Unit 1 objective: given raw images or pictures, you can obtain the digital image with using scanners and import the images into Photoshop successfully. Before the instruction: Bring two of your favorite pictures, one with large subject and the other one with small object. Examples: Large subject Small subject Lesson 1-1: Preparations of scanning images 1. Find out the scanning area of the scanner. 2. Put the pictures in the appropriate scanning area. Lesson 1-2: Resolution setting Concept: resolution Resolution is consisted of pixels. The more resolution it has, the clearer it is. Image with high resolution can represent the details with larger information (more pixels), so the file size will increase. The standard monitor resolution is 72 dpi. 72x72 pixels within 1 inch 150x150 pixels within 1 inch Using Adobe Photoshop to enhance the image quality 3
1. Launch the scan application. Launch Photoshop, select File > Import > TWAIN_32 to locate the scanning application. 2. Find the resolution setting command. 3. Choose the appropriate dpi value. The image will be set online, so the standard resolution for web images is 72 dpi. If the subject is very small, use selective tool locate the subject, and set higher resolution. 4. Choose "Scan" command to scan the picture 5. Observe the result. 6. If the image is not big enough, choose another dpi value 7. Choose "Scan" command. Continue the procedure through 3 to 5 until you obtain the best result. Practice 1: scan your favorite pictures Now it s time to scan your favorite pictures. What is the subject of the pictures? Before you scan, be sure to aware of the following condition: -How big is the subject? -What is the output of the file? (In this case, the output is web.) -How large will the image be in the web site? Then, decide the scanning resolution. Using Adobe Photoshop to enhance the image quality 4
Unit 2: Adjust images Unit 2 objective: given an image with inappropriate resolution setting, you will be able to use Photoshop image size command to find the appropriate size and set to the appropriate resolution setting. Lesson 2-1: adjusting image resolution with Photoshop Concept: resample image Resampling refers to changing the pixel dimensions (and therefore file size) of an image. When you decrease the number of pixels, information is deleted from the image. When you increase the number of pixels, new pixel information is added based on color values of existing pixels. You specify an approximation or interpolation method to determine how pixels are added or deleted. The file size will increase or decrease also. 1. If you use Photoshop to scan the picture, the image will be sent to Photoshop automatically. Otherwise, please locate the file on your local disk with File > Open. 2. Locate the image size command. Select Image > Image Size. 3. Don t select the Resample Image item. Then type the appropriate resolution value "72" in resolution box. 4. Click "OK". Lesson 2-2: cropping image 1. Locate the crop tool 2. Use mouse drag the rectangle area with crop tool to define the unnecessary edge of the image. 3. Adjust the selection area with handling points 4. Press "Enter" to crop the image. Using Adobe Photoshop to enhance the image quality 5
Lesson 2-3: transforming image 1. Select the transforming area of the image with Select > All ( or Ctrl+A) command. 2. Click right button of the mouse, the property menu will appear. 3. Select "Free transform". 4. Adjust the transformation. 5. Press "Enter". Practice 2: adjust your images Look at your images. Now you have to do: -adjust the resolution to correspond the monitor resolution. -cut the unnecessary edges -transform the image Using Adobe Photoshop to enhance the image quality 6
Unit 3: Selection tools and layers Unit 3 objective: given an image, you will be able to use Photoshop to identify the layers of the image and get familiar with using the selection tools Before the instruction: Download the image examples from course website unit 3 section. Lesson 3-1: using selection tools 1. Observe the color features of the image. 2. If the background is simple, you can use magic wand tool to select the background. 3. Use "Select > Inverse command to change the selection from background to the subject. 4. If the background is complex, you can use lasso selection tools to select the subject. When you make the selection with lasso tool, press alt key to help you make precise selection. Lesson 3-2: using layer palette Concept: layer Think of layers as sheets of transparency stacked one on top of the other. Where there is no image on a layer, you can see through to the layers below. 1. Locate the layer palette with Window > Show Layers command. 2. Increase the layer with "create new layer " command. 3. Decrease the layer with "delete current layer "command 4. Hide the selected layer with clicking "indicates layer visibility " command 5. Reveal the selected layer with clicking "indicates layer visibility " command Using Adobe Photoshop to enhance the image quality 7
6. Produce layer for selected area by "layer via copy" command. ( Layer > New > Layer via Copy, or Ctrl + J ). You can produce a new layer to retain the selected object. Practice 3: Look at your images. Now you have to do: -Select the subject of your image with appropriate selective tool -Create a separate layer for this subject Using Adobe Photoshop to enhance the image quality 8
Unit 4: Use Photoshop color adjusting commands Unit 4 objective: given an image, you will be able to use Photoshop color adjusting commands to apply the different values of hue, saturation, level and sharpness to enhance the image quality. Before the instruction: Download the image examples from course website unit 4 section. Lesson 4-1: adjusting sharpness 1. Observe the sharpness of the image. 2. If the image is too blur, locate the "unsharp masks" command ( Filter > Sharpen > Unsharp mask ) 3. Type the value of ideal unsharp mask amount value. Normally we use the default setting. 4. Click "OK" Lesson 4-2: adjusting level 1. Observe the level of the image. Concept: level Levels dialog box displays a histogram of the image. You can adjust the highlight and shadow area of the image with levels dialog box. 2. If the level of the image is not normal, locate the "levels" command( Image > Adjust > Levels or Ctrl+L ). 3. Select "auto" and observe the result. 4. If the result is not good enough, press alt and click "reset". 5. Drag the level slider to adjust the level value and obtain the best result. 6. Click "OK" Using Adobe Photoshop to enhance the image quality 9
Lesson 4-3: adjusting saturation 1. Observe the saturation of the image. Concept: saturation Saturation is the amount of the color. If the saturation of the color is 0, it will look like gray color. 2. If the saturation of the image is not high enough, locate the "Hue/Saturation" command( Image > Adjust > Hue/Saturation or Ctrl+U ). 3. Drag the saturation slider to adjust the saturation value and obtain the best result. Click "OK" Practice 4: Look at your images. Now you have to do: -Observe the sharpness. If it s not sharp enough, try to enhance the sharpness. -Adjust the level distribution if the contrast of your image is not good enough. -Enhance the saturation if it s necessary. Using Adobe Photoshop to enhance the image quality 10
Unit 5: Use Photoshop layer mode Unit 5 objective: given an image, you will be able to use Photoshop layer mode to apply the different layer modes to enhance or reduce the exposure value Before the instruction: Download the image examples from course website unit 5 section. Lesson 5-1 for selecting layer modes 1. Observe the exposure value of the image 2. If the image is overexposure, duplicate the layer and locate the "multiply" layer mode in the layer palette for the new layer. 3. If the image is overexposure, duplicate the layer and locate the "screen" layer mode in the layer palette for the new layer Lesson 5-2: adjusting layer modes 1. Select the new duplicated layer. 2. Observe the result of the applied layer mode. 3. If the exposure result is too light, decrease the opacity value to reduce the exposure value. 4. If the exposure result is too dark, duplicate the layer and locate the "screen" layer mode in the layer palette for the new duplicated layer. 5. Adjust the opacity of the new layer if the exposure value is too high Practice 5: Look at your image. Now you have to do: -Is it an overexposed or underexposed image? Try to fix the exposure with adjusting level modes. Using Adobe Photoshop to enhance the image quality 11
Unit 6: Export images Unit 6 objective: given an image, you will be able to use Photoshop to select appropriate file format and export the image for web page. Before the instruction: Download the image examples from course website unit 6 section. Lesson 6-1 for exporting with GIF file Concept: GIF file GIF file can keep file size to a minimum, and use the fewest number of colors that still give good results. 1. Select the indexed color mode ( Image > Mode > Indexed color )and change the color palette into 256 colors 2. Locate the "save as a copy" command( File > Save as a copy ), and select the "CompuServe GIF" file format. 3. Locate the file directory 4. Type the file name 5. Click "save" 6. Locate web browser to open the gif file and observe the result Lesson 6-2: exporting with JPEG file Concept: JPEG vs GIF JPEG images give you the best color and the smallest file size with compression method. If your image contains line art, use the GIF File format. 1. Locate the "save as a copy" command, and select the "JPEG" file format. 2. Locate the file directory 3. Type the file name 4. Click "save" Using Adobe Photoshop to enhance the image quality 12
5. Setup the compression value. 6. Locate web browser to open the gif file and observe the result Practice 6: Look at your image. Now you have to export the image. -What kind of file format will you choose? -Can you set up the JPEG dialog setting? Using Adobe Photoshop to enhance the image quality 13
Can you do it? Download these images from course web site. What's the problem with the image? How can you fix the problem with Photoshop? I took the picture in the early morning. The sun didn't come out at that day. Can you help me to fix the problem of the picture? Do you know how to transform the image and cut off the white edge? I think the level of the image is also not good enough. Please help me to fix the problem. Using Adobe Photoshop to enhance the image quality 14