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From Digital Foundations

Contents 1 Download Materials For Chapter 7 2 7. Image Acquisition and Resolution 3 Visual References 4 Results of Chapter 7 Exercises 4.1 Exercise 1: Creating a scanogram and understanding file resolution 4.2 Exercise 2: A brief tour of tools and panels in Photoshop 4.3 Exercise 3: Image Size, file size, and resolution 4.4 Exercise 4:From the camera to the computer

[edit] Download Materials For Chapter 7

No files were required to begin the exercises in Chapter 7; however you can download our final Adobe Photoshop file to see how we completed them.

Click here for our final Chapter 7 exercise file.

[edit] 7. Image Acquisition and Resolution

There are several ways to bring an image into the computer. The two most common are photographic in nature, that is, both methods involve exposing sensors to an item or scene in the real world. The camera or scanner then writes digital data to display that image on the screen. While the sensor technology is essentially the same, a camera is made to capture scenes with depth of field, while a scanner is made to focus on and capture just one flat plane.

Photograms are made by placing objects on sensitized paper, exposing the objects and paper to light, and then processing the paper to reveal the print. A camera is not necessary for the production of this type of graphic image. The first photograms were made by photographic pioneers William Henry Fox Talbot and Anna Atkins in the mid-1800s. This type of contact print can have an uncanny life-like presence that, like an x-ray, reduces three-dimensional information onto a two-dimensional plane without the perspective that a camera lens introduces. This overall focus and flattening of visual information results in a poetic and magical image.

A scanogram is the digital method of producing something like a photogram. It is the image made by placing objects directly on the scanner.

[edit] Visual References

Photograms have been made by photographers, artists, and designers. Anna Atkins created early renderings of natural elements. The avant-garde formal experiments of Man Ray, El Lissitzky, and László Moholy-Nagy are central works of 1920s art and design. Commercial designers such as Paul Rand used the technique for package design and book jackets. The process is fun to explore, and the results are always surprising.

http://commons.wikimedia.org/wiki/File:Anna_Atkins_algae_cyanotype.jpg
A photogram of algae, from the book British Algae, Anna Atkins, 1843. This is the first book composed entirely of photographic images.

http://commons.wikimedia.org/wiki/File:Lemons_photogram.jpg
A photogram of lemons, uploaded to Wikimedia Commons in August 2005 by user name Cormaggio.

[edit] Results of Chapter 7 Exercises

This was the result of our scanning demonstration. You will probably make something a bit different, provided you scan your own materials.

[edit] Exercise 1: Creating a scanogram and understanding file resolution

Scanners are optical input devices that use software to send the captured image from the scanning bed to the computer. Though scanning software varies among brands, all scanners operate in the same manner, and all scanning software has the same essential functions. Typically, a scanner is used to create a digital image of something two-dimensional. In this exercise, you will scan a three-dimensional object.

1. Place your object on the scanning bed. If the lid does not close, put a dark piece of cloth around the scanner so ambient light doesn’t leak in and interfere with the exposure during scanning (a jacket or dark sweater will work.) We are scanning a flower that fell to the ground— it lies flat, so it will be easy to close the lid on the scanner.

2. Open the scanning application.

At home we use VueScan, a stand-alone application that seems to work with most scanners. The Epson scanners in our labs are operated through Photoshop’s Import feature, located in File > Import > Scanner Name. If you are not sure which software interface to use, please consult your scanner’s documentation.

3. The scanner may automatically create a preview of whatever is placed on the scan bed. If it does not, a preview of the last item scanned may be visible. To create a preview, look for a button labeled with a word like “preview” or “view” or “prescan.”

The scanner will digitally capture the entire scan bed area. The preview of the flower takes up a small part of the entire scan bed.

4. If your object is smaller than the scan bed, select just the area that you want to scan by marqueeing over the image area. You may have to look for a selection tool in the scanning software’s toolset, or you may be able to just click and drag over the preview without changing to a tool. At this point, your selection marks the location of the object on the scan bed. If you lift the lid and move the object, you will have to re-preview in order to tell the scanner where to locate the selection.

Notice the selection edges are very close to the edges of the flower.

5. Choose your resolution. This is the crucial step. Before scanning, the artist must decide upon the file’s input resolution.

Printed images are measured in inches Print resolution is often 300 dots per inch. You can get away with printing at 200 dots per inch in non-commercial situations, but the industry standard for printing on a digital printer is 300 DPI. This may vary by output type, so always ask the printer for the proper file resolution. Effective resolution: Are you planning to enlarge or reduce a digital image before output? Once pixels are acquired, image data can’t be added, so any image enlargement will result in loss of quality. Reducing an image is no problem, but remember to keep the original file in the largest size and use Save As to create a smaller version. Effective resolution is the magnification factor multiplied by the printing resolution. You should end up with a number that corresponds to your targeted output device. For example, if you are scanning a 4x6 inch photograph to print it on the full page of an 8x12 inch photo inkjet paper at the printing resolution of 300 DPI, you will scan the original image at 600 DPI. The magnification factor is 2 and the printing resolution is 300 DPI. The effective resolution is 300*2. Resolution for screen presentations: Any image that will only be used on-screen, for instance on a website or in a video, will only need to be saved at screen resolution. Although monitors may vary, 72 dots per inch is a very common screen resolution. Image files saved at screen resolution are much smaller in file size than images that are saved for printing. Monitors are measured in pixels: For any image that will be used only on-screen and is not intended for eventual printing, the only goal should be to create the number of pixels you want to display. If you want to display a 500-pixel-wide image on a monitor, then scan it so it is 500 pixels wide, and you're done. If your scanning software requires you to choose a dpi or ppi resolution, choose 72 and make sure your scan remains 500 pixels wide.

Different output devices require different resolutions to produce quality output. Resolution is the number of pixels displayed per inch (PPI), also called dots per inch (DPI). In 1984, when Apple pioneered consumer WYSIWYG text, a way was needed to translate font sizes on screen to printed output dimensioned in inches. The early Macintosh computer screen used a logical inch made of 72 pixels, or 72 dots per inch. Windows was programmed to assume a monitor displays 96 dots per inch. Printers can easily squeeze 300 dots into an inch, and some go much higher. Knowing what kinds of resolution the intended output device has will help you decide what input resolution to use.

Here we cropped the scan area to the edges of the flower. It's almost 1.5 by 2 inches. This is important information, as it will help to determine what resolution to use when scanning the file.

6. Using the guidelines above, choose a resolution and be sure that the color mode is appropriate (black and white line art, grayscale, or color).



We are scanning at 600 dots per inch. We know that we can make a high quality print on an inkjet printer at 300 dots per inch. Since 300 multiplied by 2 is 600, we will be able to print this scan at close to 3 by 4 inches, or the width and height multiplied by 2.

7. Select the TIFF file format and name the file. File formats such as JPEG, PNG, and PDF compress the size of the file, and may result in a loss of digital information. File formats such as TIFF and PSD are not lossy, and are therefore better format choices for high quality scans. In VueScan, we set the name and format of the file using the Output tab before creating the scan.

This is our final TIFF file as seen in Apple’s image viewer application Preview. We will be opening this file in Photoshop for the next exercise.

8. The last step is to click on a button that reads something like “scan” in order to actually scan and save the file. Depending on your software, steps 7 and 8 may need to be switched.

9. Depending on your scanning software, you may have to specify the name and file format in a Save As dialog box after pressing the Scan button.

[edit] Exercise 2: A brief tour of tools and panels in Photoshop

1. Open the scanogram file in Photoshop by dragging it to the Photoshop icon in the dock or using File > Open in Photoshop.

2. Set the default workspace by clicking on Window > Workspace > Essentials.

In the Creative Suite programs, panels are accessible from the Window menu. Panels are also docked on the right side of the screen. All panels can be minimized or closed and reopened if needed. As you become familiar with Photoshop, you will be able to minimize and do without certain panels so there is more room for viewing the image.

Notice that the tools are located in the Tools panel on the left side of the screen. You can view the tools in a single or double column.

3. Click once on any tool and notice the Options bar at the top of the screen. As with tools in Illustrator, most Photoshop tools have adjustable values. In Photoshop this is done in the Options bar.

This is an image of the Options bar. For this screenshot, the Rectangular Marquee tool was selected. When a different tool is selected, its options are shown here.

4. The Navigator panel can be used to explore various areas of an image. An image that has more pixels across or down than the monitor has will not fit on screen at 100 percent magnification. The Navigator can be used to move around an image that is large or magnified, but you will soon learn shortcut keys to use instead of this panel. Move the slider on the bottom of the Navigator panel all the way to the right to zoom all the way in to the image.

The red outline over the thumbnail display indicates which part of the image is viewable on screen. Notice the slider is pushed all the way to the right, and in the bottom left corner we are zoomed in to 3200 percent.

5. Enlarge the view of the image by zooming in, and the individual pixels that comprise the image are in plain view.

Pixel: The word pixel is a combination of two words: picture and element. A pixel is the smallest unit of color information in a digital image. Bitmap or Raster images: A digital file is considered bitmap or raster (two words used interchangeably) if it is composed of a grid of pixels. Raster is the German word for “grid.” Photoshop is the Creative Suite application that is primarily used to work with raster images.

Hot key: Command+0 will change the viewing percentage so the image is as large as it can be on your screen. This hot key works in all of the Creative Suite applications.

6. Double-click the Zoom tool in the Tools panel to see the image at 100 percent. It is important to view digital images at 100 percent as this is the “true” representation of the file. This is as good as it gets on the screen.

In the Zoom tool options bar, locate the zoom out button (Zoom tool with a minus sign). Click on this and then click anywhere on the image. Keep clicking and you will continue to zoom out of the image. The Actual Size button will also display the file at 100 percent. The Fit Screen button will make the image as large as it can be viewed on your screen.

7. Now we'll try some key commands. Zoom in by using Command+= and then use the Spacebar key to access the Hand tool.

Hot key: Holding the Spacebar on the keypad changes most tools to the Hand tool. This is useful for quick, temporary access to the Hand tool.

Hold Spacebar and use the mouse to click and drag on the image. This moves the image around within the workspace. Using the Hand tool is a more efficient work habit than using the scroll bars.

[edit] Exercise 3: Image Size, file size, and resolution

1. When working with scanned files or files input from a digital camera, the only layer in the Layers panel is the Background layer. A layer is like a single sheet of transparency paper. An empty layer is transparent. When a scan or digital photograph is first opened, Photoshop puts it on the Background layer. Look in the Layers panel (Window > Layers) and notice that the Background layer is locked. Double-click on the words “Background Layer” in the Layers panel to rename it through the Layer Options dialog. When you rename the background layer it is automatically unlocked. Unlocking the background layer is a good habit, because you will name it and prepare the layer for further manipulation.

Tip: A layer’s name, thumbnail, and mask thumbnail launch different actions. If you get an unintended dialog box after double-clicking on a layer, press Cancel, then try again by double-clicking specifically on the name of the layer.

2. The Status bar runs along the bottom of the document window. Click on the area of the Status bar that reads “Doc:” followed by a number in kilobytes or megabytes. This area reports the file size. Here you will see the width, height and resolution of the image. To see a visual representation of the printed size of the digital file, choose File > Print and notice the print preview. Our print would be very small at the current file settings. Now press the Cancel button to return to standard editing mode.

3. Click Image > Image Size to see the resolution of the image.



Our scan is about 1.5 by 1.9 inches at 600 DPI.

4. Make sure Resample Image is not checked, so that Width, Height, and Resolution are linked together. Notice that the pixel dimensions at the top of the Image Size dialog box are no longer editable fields. The pixel dimensions will not change if a change is made to the editable areas beneath Document Size. Modifying any one of the variables Width, Height, or Resolution, results in corresponding changes to the other two variables. We set the resolution to 300 DPI. This resulted in a width and height twice as large as the original scan.

By using the Image Size dialog box with Resample Image unchecked, you can change the dimensions of the printed image without changing the number of pixels in the file. This is a good thing — in general you don’t want to change the number of pixels within the image.

Pixels are created during image acquisition, on a scan bed or within the digital camera. Pixels can de discarded, but the only way to add new pixels is to rescan or re-capture the digital file using a higher resolution. Photoshop cannot add meaningful new image data, it can only interpolate information based on the surrounding pixels, and the result is usually a soft and mushy image.

6. Click OK. Notice that nothing seems to happen to your file on the screen. This is because there was no change to the actual number of pixels in the file. What changed is the amount of pixels that will be printed in one inch when the image is printed. Use the Print preview to examine the result. By nearly halving the resolution, the dimensions of the printed image have doubled while the pixel dimensions of the file are the same.

The print preview shows that the scan will print at a much larger size than it would have printed before changing the resolution settings in the Image Size dialog box.

7. Choose File > Save As to change the format of the file from TIFF to Photoshop (PSD). The name of the file does not have to change, as the change in extension will create a new file. The original scan remains untouched as a TIFF while the document that was just altered has become a derivative with the same name but a .psd file extension. Always save using the native or master format of the editing application associated with that kind of file.

[edit] Exercise 4:From the camera to the computer

Digital cameras use memory cards to store file information. To send the images from the storage device to the computer, the camera is connected to the computer via a cable. Alternatively, the memory card can be taken out of the camera and inserted in a card reader connected to the computer to be read like a small hard drive or jump drive.

1. If you connect your camera to the computer with a cable, then you will use an application to read the images. On a Mac, iPhoto may automatically launch; however, our favorite Mac application is Image Capture. If you are using a Mac and don’t see Image Capture on your dock, look in the Applications folder for it. To transfer files from the camera to the computer with Image Capture, connect your camera to the computer (USB or Firewire), launch Image Capture, and press the Download All or Download Some… button.

A card reader will appear on the desktop as an external hard drive. Simply drag and drop the folder of image files from the card reader to the desktop or documents folder. Once images are copied to the desktop, it is safe to delete them from the card.

2. By default, images will be downloaded and saved to the Pictures folder on the Mac hard drive. Use the scroll menu next to Download To to change the location of the files by clicking Other… and then selecting the desktop, or a folder of your choice.

3. Download Some… will display thumbnails of each image, and you can choose which images to download by selecting multiple files with Command+click.

After clicking Download Some... small thumbnails of each image appear. In this illustration, the highlighted images have been selected by holding the Command key and clicking once on each thumbnail.

4. When you are finished choosing images for download, click the Download button.

5. Quit Image Capture. Open the folder you selected in step 2 to locate the image files on your hard drive.