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Ten Steps to a Perfect Scan

If you don’t see the options listed below, look in the scanner software for ‘Advanced’ or ‘Expert’ controls or tools. The ‘Basic’ or ‘Quick’ options will not give you the desired results.

1) Place the original on the scanner.

TIP: Before you place the original on the scanner, clean and dry the glass thoroughly. Fingerprints and dust will ruin your scan and require re-touching. Don’t spray ammonia directly on the glass. Instead, spray glass cleaner, or monitor cleaner, on a soft, clean cloth and wipe with that.

TIP: Make the original as flat as possible. You may have to lay a book on top of it, or hold it with your hand during the scan. Most scanners have a removable cover. (Don’t break the glass or force the cover.)

2) Launch the scanner software . . .

a) as a stand-alone program. This makes ‘batch scanning’ easier, since the program allows you to scan many images quickly, one after the other, saving the files as you go without closing the scanner program. The scanner program is stored in a folder that was created when you installed your scanner driver. Check your Programs or Applications folder for the name of your scanner.

b) through Photoshop. Launch Photoshop first, then go to the File menu/Import, choose ‘Twain Acquire,’ or the name of your scanner software. This method lets you scan only one image at a time, but each one is opened automatically in Photoshop as soon as you scan it.

3) Choose Pre-scan, or ‘Preview’. This acquires a quick scan of the entire scanning area.

4) Make a Selection. Usually this is done by simply clicking and dragging a marquee around the portion of pre-scanned image you want to acquire. Don’t scan the entire glass unless you need the entire area. But try to get just a little more of the image than you absolutely need, in case you want to re-crop it later.

a) You can adjust your selection by clicking on a side or corner of the selection boundary and dragging it.

b) You can delete a selection. If you have multiple selections, you can usually delete each one by clicking on it so that it’s active and pressing the Delete/Backspace key.

5) (optional) Magnify or Zoom your selection area. Look for ‘Zoom’ commands or an icon of a magnifying glass, or a plus/minus symbol. The scanner interface will enlarge the view of the selected area so you can make a more precise selection. This does not make the resulting scan larger.

6) Choose the target Image Type or Color Mode. There are three basic image modes:

a) Color (also called ‘Color Photo,’ ‘millions of colors,’ 24-bit, 32-bit, etc.) This will result in a full-color image. It may be made of literally millions of colors. 24-bit will give you plenty of information for most print projects and more than enough for all Web projects. (24-bit means ’24 bits of data per pixel.’ This data describes an 8-bit code for brightness, hue and saturation for each pixel. Higher amounts of information may be necessary for projects on film.)

b) Grayscale (also called ‘Black and White Photo,’ 256 grays, and 8-bit). This will result in an image that contains 256 levels of value, or grays, but no color information. (8 bits of brightness data per pixel.)

c) Black and White (also called ‘Line Art,’ ‘Drawing,’ ‘Text,’ ‘Bitmap,’ and 1-bit) This will result in an image which contains only two colors – black and white, and no grays. This is good for scanning text.

TIP: When scanning text, choose a resolution of 600ppi. You will get smoother, more readable text.

7) Choose your Target Resolution, depending on your project

a) For the Web, mobile device or projected slide show, choose 72 dpi/ppi. (You can choose a higher resolution of 144 or 288 in order to correct the image but you must reduce it later to 72 dpi/ppi)

b) For Print, choose 300 dpi/ppi for photographic grayscale (8-bit) and color (24+bit) images and original art. Choose 900 dpi/ppi for true black-and-white (1-bit) images of text and line art.

8) Enter your Final Dimensions OR Target Scale (percentage of enlargement or reduction). This may be expressed as an absolute number of inches or pixels, width by height OR as a percentage of the actual current size.

a) In the Dimensions fields enter your desired dimension for Width or Height. Type your largest target dimension in one of the fields. If your scan area is horizontal, type the width. If your scan area is vertical, type the height. For a print project, use inches (.in). For the Web, mobile devices and projectors, use pixels (.px). For example, some standard monitor dimensions are 1024 pixels wide x 768 pixels high, or 1280 x 960 pixels for a higher-resolution monitor. OR. . .

b) In the Scale field, enter the percentage of enlargement or reduction. If you want the resulting image to be twice as large, type 200%. To figure out the correct percentage, divide the largest dimension of your desired result by the size of the original. (Use a calculator). For example, if your original image is 6 inches wide, but you need it to be 2 inches wide, divide 2 by 6. The result will be a 33% reduction. If your original image is 2 inches wide, but your desired dimension is 6 inches wide, divide 6 by 2. The result will be a 300% enlargement. What you want is always the first number.

9) (optional) Adjust the scan using ‘expert’ tools in scanner software. (Brightness, Contrast, Color, etc.). Most scanning programs do not give a detailed preview.

TIP: I prefer to work on the image in Photoshop, which offers a much better preview and can be set to emulate the color and value of your output.

10) Choose ‘Scan’ or ‘Save’ (also called ‘Final Scan,’ or ‘Approve’) Save the scan in the appropriate file format:

a) for Web and mobile, save as JPEG or GIF. Varied or blended values look better in JPEG format. Flat areas of solid color look fine in GIF format and the file size is highly compressed.

b) for Print, save as TIFF. TIFF is the standard for raster images. (EPS and PDF are not commonly used for raster images, but it works as well as TIFF.)

Scanning halftones, such as images in books or magazines, or other printed material. These images present a real problem. The scanning process creates a pattern, like an invisible grid. The image you are scanning is also broken up into a halftone pattern. Overlaid together, the two patterns create an undesirable new pattern, called a moiré pattern (or an interference pattern). It looks like a wavy plaid, stripes or overlapping rings running through the image.

For this reason, try to always scan original images, like photos or artwork. If you must scan a halftone (screened) image, try to minimize the moiré pattern by rotating the original slightly – about 5 degrees - on the glass of the scanner. If the pattern persists, try rotating it up to 15 degrees, and try rotating in the other direction. Choose the best of the three scans and open it in Photoshop. Zoom in and out to check whether the pattern persists. One view will reveal it better. Open the Filter menu / Gaussian Blur and adjust the filter until the pattern disappears as much as possible without blurring the image. Then choose the Rotate Tool, or Edit/Transform/Rotate, or the Move Tool, and rotate the image back to true vertical.

Changing Dimensions and Resolution after Scanning

Reducing a scanned image is fine, but enlarging a scanned image will create problems. Because a digital image is made of tiny tiles, called pixels, they become visible whenever you enlarge the image. This is true of all digital images, whether captured with a scanner or digital camera, or created from scratch in a paint program. You should always get a new scan of the original at a higher resolution or larger dimensions, or take a new, high-resolution digital photo, or create a higher-resolution image, instead of enlarging the existing file. But if you absolutely have to, this is a reliable way to do it.

TIP: There are some software programs and Photoshop plug-ins that will help you enlarge an image with less degradation, such as Imagener, and Genuine Fractals.

1) In Photoshop, go to the Image menu/ choose Image Size

To Reduce or Increase Resolution:

a) Un-check Resample image.

b) Change the resolution to the one you need. For example, if you originally scanned the image at 300 ppi for a print project, and you need to use it in the Web, change the resolution to 72 ppi. You will notice that the image dimensions have also changed.

c) Re-check Resample image

d) Change the dimensions to match your final dimensions.

To Reduce or Increase Dimensions:

a) Un-check Resample image.

b) Change the dimensions to the ones you need. You will notice that the resolution has changed.

c) Re-check Resample image

d) Change the resolution to match your final project – 300 ppi for print, 72 ppi for Web.

If you increase either the resolution or the dimensions of the image beyond 120% of the original, the image will become visibly degraded. Very gentle blurring using Gaussian Blur and cautious re-sharpening using UnSharp Mask will help to soften the ‘jaggies’ that remain from the original pixel tiles. Be careful -- you may also melt away the details of the image, and it will never have the quality of a high-resolution scan.