IT Services

Introduction to Graphics Scanning with Adobe PhotoShop


1. Introduction

Scanning of photos, drawings or other pictorial material can be done via any of the graphics applications installed on the OUCS Help Centre scanning PCs. One of the most popular applications for this purpose is Adobe PhotoShop, but very similar procedures can also be used with PaintShop Pro, Corel PhotoPaint etc.

2. Starting up PhotoShop

Start up PhotoShop by double-clicking its icon on the Windows desktop.

3. Making a Scan

From the PhotoShop [File] select the [Import] option, then the [TWAIN_32...] sub-option.

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The Epson TWAIN scanning module should then be loaded.

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Before, you start scanning, you need to specify three sets of details that will affect how the scan is made:

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The Image Type - for real colour photos 24-bit Color (Std) is the best setting to use. For pictures scanned from magazines or newspapers, use the 24-bit Color De-Screening. For black-and-white diagrams, the Line Art setting may be preferable. The Help button will give more information about all the options. Choosing an image type, sets good default values for the other settings such as Pixel Depth which generally should not need changing. Click OK to accept the new settings.

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The Destination - choose the option that best corresponds to where the image will be displayed or printed. The most commonly used options here are Screen/Web or whichever of the printer options is most relevant. The Help button will give more information about all the options. Choosing a Destination, sets good default values for the other settings such as Resolution (measured in dots per inch). The higher the resolution, the better the image quality but the bigger the size of the image file.

For a printed original, the best guide is to choose a resolution that matches the resolution of the intended output device. The printed or displayed image will then be about the same size as the original.

For a slide original, the resolution needs to be higher, but again it depends how the image is to be used. A 35mm slide scanned at 400dpi will occupy about a quarter of a typical display screen. At 800dpi, it will occupy the whole screen.

The [Unsharp Mask] option performs automatic sharpening of photos. Click OK to accept the new settings.

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4. A Preview Scan

The next step is to make a preview scan which allows you to check your settings and also to select the precise area you want to scan. Select the final scan area is done dragging across the required area with the mouse. The outline rectangle can then be further adjusted by dragging its edges or corners as desired. Other aspects of the image can be adjusted at this stage using the Adjust controls.

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5. The Final Scan

Leave the Preview window open and return to the main TWAIN window. Click on the Scan button. The specified area will then be scanned and the result placed in a new PhotoShop document window.

6. Saving Your Scan

After making the scan, click on the TWAIN Close. This will take you back to PhotoShop. You can then Save your scanned image. Use the [File/Save As] option to choose where to store the image and the storage format to be used.

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The most commonly used storage formats are JPEG and GIF.

6.1. JPEG Files

The JPEG file format is very widely used for photographic images. It provides a compression option which can give a dramatic saving in the storage requirements for an image, although possibly at some loss in image quality.

If you choose the JPEG option, you then need to set the compression level to be used. In PhotoShop, this is specified as a value ranging from 1 (most compression and producing the smallest file but with the greatest reduction in quality) to 12 (least compression, largest file, no loss in quality). The actual file size that will be produced at a particular compression setting is shown at the bottom of the JPEG Options windows.

Figure photoshop8.gif []

6.2. GIF Files

The GIF file format is mostly used for line-drawings, computer screen-shots, logos etc. It allows a maximum of 256 colours in the image. Although GIF does offer compression, it is extremely efficient for storing images containing area of a single colour. If the GIF image is specifically for use on a web page, the [File/Save for Web] menu option provides additional options for saving GIF files.