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Rangefinder Magazine
June 2003

Scanning Basics: by Nathan Segal
How to Achieve Quality Scanning Results

Scanning is an important task that many of us have to carry out, whether for a print project or to build catalogs of images for clients. But the process can be mired in difficulties that can ruin your scans. Here are a variety of tips designed to ensure scanning success.

This image is a scan of a photographic print that was output on Kodak medium weight photography paper. It was scanned in Photoshop 7.0 running under Windows 2000 Professional using a UMAX Astra 1220U scanner with the software that comes bundled with the scanner. The scanning settings were: Default, B/W Photo, 300 dpi, with the Auto Adjust checkbox enabled and was saved as a PSD (Photoshop Document) file. No other adjustments were necessary. Photographer: Tom Clay.

Calibrate Your Monitor. Before you get started, make sure that your monitor has been properly calibrated. If it hasn’t, you won’t be able to rely on anything that you see. This is an important area that many users overlook.

Clean the Scanner Surface. When using a flatbed scanner, make sure that the scanning glass surface is clean. Nothing will ruin your scans faster than a surface covered with fingerprints, streaks, and/or dust. Some purists will say that you need to clean both sides of the glass, but this may not be possible as some glass surfaces are sealed within the scanner struc-ture. If you can remove the glass, do so with a thin-bladed knife or screwdriver. But don’t force the glass or it may break.

To clean the glass, spray glass cleaner onto a soft cloth or crumpled piece of newspaper. Wipe the bottom of the pane first, then replace it and clean the top. Next, run a scan of the surface alone to check for dust or streaks. These should be immediately apparent and will indicate the need for further cleaning, if necessary.

Use a Slide Scanner for Transparencies. If your intention is to scan slides, don’t use a flatbed. They are not the best option for this type of work. Instead, buy a slide and negative scanner. When using a slide/film scanner, scan images at the maximum optical resolution.

Check Resolution Require-ments. Before beginning a graphics project, it’s important to know which resolutions are necessary. For a quick reference, Web images use a resolution of 72dpi. Newspapers use resolutions from 125dpi to 170dpi. High-quality brochures and magazines, such as this one, use resolutions from 200dpi to 400dpi. And for books, the range is generally from 175dpi to 350dpi.

Start with a High Quality Original. Once you have determined the resolution(s) that you need for your graphics, the next step involves transferring the images to your computer. Before you even begin the scanning, it’s essential to start with a high quality print, negative, or transparency (slide). While image manipulation programs such as Adobe Photoshop (http://www.adobe.com) can correct for flaws in the original (for example, its tone, brightness, etc.), you cannot bring out elements that don’t exist in the original image. Also, a high-quality original means less work for you later.

	This screenshot is of the dialog boxes used to change the background color on your monitor to a neutral gray. The first step is to open the Control Panel folder, then click on the Display icon. At the top of the dialog box, click on the Appearance tab, then on the color swatch on the lower right. This brings opens a pop-up of color swatches. Click on the “Other” button at the bottom, which brings up the Color dialog box. Select one of the white swatches under the Custom Colors heading, then type 127 into each RGB field. Make sure the swatch (now gray) is selected then click on “OK” twice. Your background screen will now be gray.

Scan at the right size. Scan the image at the right size for your application (or as close as possible). While you can scale images up or down, it is important not to exceed 20 percent in either direction, or quality may suffer.

Cropping. Before doing your final scan, crop the image. If you don’t, the image will be larger and it will take more time to scan. If you need to do additional cropping, use a photo-editing program, such as Photoshop or Paint Shop Pro. Once the image is scanned, save it as is with no modifications. Save edited scans as separate files.

High-Quality File Types. For high-quality imagery, some common file types are PNG and TIFF (Tagged Image File Format), but these are not the only choices. PNG and TIFF are excellent for overall quality and integrity. PNG offers up to 48-bit true color and 16-bit grayscale. PNG also offers compression options and is lossless, meaning that no matter how many times you save the file, you will not lose data. TIFF has long been recognized as an industry standard and also offers compression options. The TIFF format supports RGB, CMYK (cyan-magenta-yellow-black), LAB, indexed color, and grayscale with the use of alpha channels. The TIFF format also offers compression options, as well.

Note: Do not use the JPEG format. By definition, it’s a lossy format, meaning that it will eliminate data each time you save the file. And once it’s gone, you can’t get it back. Over time, JPEG compression will add artifacts and smear edges and lines.

This image is a scan of a digital print that was output using an Agfa DLAB 2. It was laser exposed on photographic paper. It was scanned in Photoshop 7 running under Windows 2000 Professional, using a UMAX Astra 1220U scanner with the software that comes bundled with the scanner. The scanning settings were: Default, True Color RGB, 300 dpi, with the Auto Adjust checkbox enabled. The file was saved as a PSD file. Photographer: Nathan Segal

Moiré Patterns. This is a problem that comes into play when scanning printed images such as those found in magazines or promotional documents. There are many reasons why this might occur, but one has to do with the way that the scanner picks up the dots in the image. Occasionally, during the process of scanning, a Moiré Pattern appears over the entire surface of the scan, ruining your image.

There are several methods of removing Moiré from your images or preventing it from happening entirely. One approach is to use the Descreen filter that comes with some scanning software. It allows you change the lpi (lines per inch) setting to match the one used to print the image you’re scanning. As a starting point, try using 133 lpi for magazines, 175 lpi for art-work and 70 lpi for newsprint. This filter should only be used when scanning printed documents and/or images.

If that doesn’t work, here are some other techniques. If you try one and it doesn’t work, undo the change before you try the next technique, otherwise the effect be-comes cumulative.

	To access Adobe Gamma, open the Con-trol Panel folder and click on the Adobe Gamma icon. When that opens, you’ll see a dialog box that gives you a choice of using the Wizard or Control Panel. Choosing the Control Panel and clicking on the “Next” button will bring up the dialog box above. Under Gamma, you’ll see a check mark by “View Single Gamma Only.” If you remove the checkmark, you’ll see three RGB screens for more precise color adjustment.

The first technique you should try is to open the Filters menu and choose Noise, then Despeckle. If it works, there will be some blurring throughout the image. The blurring is acceptable as long as the Moiré pattern is gone, but if it isn’t, undo the command and move on to the next technique, blurring.

Under the Filters menu, choose Blur, Gaussian Blur. In the Gaussian Blur dialog box, the default setting is 1. Make sure the Preview window is active, and then reduce the amount of blur one point at a time, such as from 1.0 to 0.9 to 0.8. Keep reducing the amount until the Moiré pattern reappears, and then increase the setting until the Moiré pattern disappears. If this technique doesn’t work, undo this command and move on to the next technique.

Another approach is to click open the Image menu and choose Image Size. In the Image Size dialog box, reduce the resolution by half and click OK. That should remove the Moiré.

A last ditch technique (and probably the simplest one) is to scan the image at an angle (which you’ll have to straighten later). Doing this should finally eliminate the Moiré pattern.

Black and White Scanning
There are three scanning techniques that you can use for black-and-white scanning. The first technique is line art of a black-and-white document, depending on your software. It is a one-bit scanning technique where the scanning software uses one bit of data to define a dot. Since bits are either a 0 or a 1, the dots are either white or black. A multitude of these will create a black-and-white image. This technique is perfect for scanning black-and-white text or pen and ink drawings. Images of this type create the smallest possible files.

The last technique is known as grayscale scanning. Where this ap-proach differs from the ones above is that it is an 8-bit process, meaning that this scan is capable of recording 256 levels of gray. White is represented by the value 255 and black by a value of zero. As such, it is the recommended technique for scanning black-and white photographs that you wish to be of high quality. In terms of file size it will be eight times as large as a line-art file, but it will still be smaller than a color image.

Nathan Segal is a Photographer/Artist who works with Digital Imagery, Painting and Illustration. He’s been writing articles for the last five years. Visit his website is: www.cosmicstock.com.