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  • The Computer Genealogist: Improve Legibility of Online Records with Image Processing Software

    Eben W. Graves

    Published Date : February 16, 2005

    The Vital Records of Massachusetts 1841 to 1910 database on is an important resource for all genealogists with Massachusetts roots. The index is complete and easy to use. The records themselves are produced as images of the handwritten originals and are being added to the database over time. The images include data elements that most members will value, such as precise dates, parents’ names and birthplaces, and occupations.

    Viewing the online records can be frustrating, however, because the quality of the images ranges from very clear to almost illegible. One problem frequently encountered is that of low contrast, due either to over or under exposure of the image itself. Such defects probably originated when the document was photographed and would therefore also be encountered when the records are viewed on microfilm at the Massachusetts Archives (the original state returns are also kept at the Massachusetts Archives).

    Members who have a photographic image processing application already have the means to improve the legibility of documents that suffer from low contrast. I use Adobe® Photoshop Elements 2.0[1] and have achieved similar results with the software that came with my digital camera. The steps used to improve the legibility of a database image are the same as those used to improve the quality of a photograph. The images on the database are, after all, nothing more than digitized photographs. Although Photoshop is widely viewed as the industry standard in image processing, Microsoft’s® Digital Image Pro and Paint Shop® Pro are two other examples of digital imaging software.[2] The following information is specific to Photoshop, although the end result can be achieved using other brands.

    When a poor image is encountered, the first step is to save the image onto your computer’s hard disk. Start by using the viewer’s zoom and pan controls to position the image on the screen. Zooming out allows the capture of a larger portion of the document while zooming in results in a higher quality image.

    Improve Legibility 01

    Position the mouse cursor anywhere over the image and click once with the right mouse button. This step brings up the following command menu.[3]

    Then move the mouse cursor down the list of commands until Save Image as . . .[4] is selected (indicated by blue highlighting) and click the left mouse button once. This step brings up the Save As dialogue box, which allows you (1) to enter a file name for the image and (2) to specify the location or folder in which it is to be saved. The dialogue box also allows choosing between bitmap files and JPEG files. I have used bitmap files because they produce slightly clearer images, but at the cost of taking up much more space on the computer’s hard disk. In many cases, the extra disk space consumed by the bitmap image will not be justified by the minor improvement in the image’s quality.

    It is important to remember the names of the folder and of the image itself so that you can find them again, as well as the file type used (bitmap or JPEG).

    If you are using Microsoft’s Internet Explorer[5] web browser, it is possible to save an entire page or at least most of it (Figure 4). First in the image browser, use the Image Properties command in the right click context menu to learn the size of the whole photograph. Next, zoom out to the maximum amount possible or use the Fit Image to Frame command in the context menu. Then, use the Frame Size command in the same menu to choose Custom Size and make the frame size the same size as the entire photograph. You may see that the image does not take up the entire page, in which case it should be dragged so that the top and left margins are in the upper left-hand corner of the image browser window. The image may be wider than the maximum width of the viewer, 2,048 pixels, but this should not matter because the page itself is usually not as wide as the complete database image. For example, the full image used in the example was 3,400 pixels wide and 1,900 pixels high, but after the unused pixels were removed, the page (Figure 4) took up only 1,357 by 1,237 pixels.

    The image resulting from the last step will probably not fit on your computer screen, but again that doesn’t matter because the point is to save the image to the computer’s hard disk, not to look at it. But you could use the Internet Explorer scroll bars to view the enlarged image window if you so wanted. The file will be very large if it is saved in a bitmap format: the page above from the town of Rockport required 11MB; after it was cropped to show only the page, it took 4.8MB (The JPEG file of the same page took only 328KB before cropping).

    Improve Legibility 02

    The next step is to enhance the image’s legibility with image processing software. Open the image processing application and load the file that you saved in the previous step.

    “Low contrast” is an easy way to say that the bright and dark areas of an image all fall within a narrow range of values. This condition can be shown graphically in what is known as a light level histogram. In Photoshop Elements, this graph can be viewed by clicking on the Enhance command on the menu bar, then on the Adjust Brightness/Contrast command, and finally on the Levels command.

    Note that the image values, shown in black, are clumped into a very narrow, high curve that takes up less than a quarter of the width of the graph. The narrowness of this curve is typical of a low contrast image. The position of the curve toward the left hand, or dark, side of the graph is symptomatic of an underexposed image.

    Underneath the graph, there are three adjustment controls, called sliders, for shadows, midtones, and highlights. These can be manipulated by holding the mouse cursor over them and pressing and holding down the left mouse button, while moving the mouse to the left and right. In the lower right corner of the window, be sure to check the Preview box so that the effect of the adjustments can be seen as they are made.


    Improve Legibility 03

    By moving the sliders, the tonal range and the contrast of the image can be increased. Move the slider on the right first — the one for the highlights in the image — to the left until it is just under the righthand tail of the histogram. This step alone will probably make the document readable. Next, move the left slider to the right until it is just under the lefthand tail of the histogram. These adjustments result in an immediate improvement to the legibility of the document.

    When the tails of the curve are long and flat, as in this example, further improvement can be realized by moving the sliders closer to the middle, to where the flat tails join the steeper part of the curve. Again, moving the right-hand slider will have the most dramatic effect. Because the Preview box was checked, the effect of moving the slider back and forth can be seen immediately. The sliders can be moved independently of each other until the legibility of the image has become optimized. Click on OK when you are satisfied with the results.[6] Very satisfactory results can often be achieved simply by clicking on the Enhance command on the menu bar and then on Auto Levels or on the Auto button in the Levels box instead of adjusting the individual sliders.

    The last step is to save the enhanced image, if desired, or to take notes from it now that it’s legible.


    1 Adobe, Photoshop, and Photoshop Elements are either registered trademarks or trademarks of Adobe Systems Incorporated.

    2 Microsoft and Digital Image Pro are either registered trademarks or trademarks of Microsoft Corporation.

    Paint Shop, and Paint Shop Pro are either registered trademarks or trademarks of Corel Corporation.

    3 The menu can also be accessed by clicking the next to last button on the right on the tool bar above the viewing frame.

    4 Menu and toolbar commands used in the examples are shown in sans serif type.

    5 Microsoft and Internet Explorer are trademarks of the Microsoft Corporation..

    6 Similar results can be achieved using the Brightness/Contrast command instead of the Levels command in the Photoshop Elements Enhance: Adjust Brightness/Contrast command. The Levels dialogue box gives the user a little more flexibility.

    Eben W. Graves lives in South Norwalk, Connecticut, and is currently working on a genealogy of the descendants of Henry Sewall of Coventry and Manchester, England, and Newbury and Rowley, Massachusetts.

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