by Natalie D. Cottrill
One of the wonderful things that computers can do for genealogists, is to help us organize and preserve our old documents and photos. But, because today's home scanners offer higher resolutions and finer quality scans than ever before, their output produces really huge files that can quickly grab all your disk space.
Naturally, most of us think "bigger is better," or "higher quality" is better, but in the world of scanning and archiving, it is important to consider the purpose of the image scan, so that we don't "go overboard," scan documents at a higher than necessary level, and then run into expensive storage needs. Storing images in some external storage device (CD-Rom, DVD, external hard drive, etc.) is a good solution to keeping your working hard drives free of large sized scanned documents. Here are some things to consider when scanning your documents and photos.
- If you intend to print a regular-size (4- by 6-inch or 5- by 7-inch) photo or a fairly good quality document, then a 300-dpi scan set at 100% size will give you as much detail as you need. Even with a high-resolution color ink-jet printer on quality photo paper, the results you will see between a 300-dpi scan of the image and a 600-dpi scan are indistinguishable as long as you print the image the same size as the scanned original.
- If you scan a photo or document to send via e-mail to a friend or to post it on the Web, it might be best to consider a 72- or 100-dpi scan at 100% size. This file will take up less memory and therefore it will be uploaded and downloaded faster in an email. Your recipient's modem speed might be so slow that it would take them hours to download a larger file. Also, some ISPs will block large file attachments via email. You might want to make sure, too, that the scanned image is no larger than 5" wide, or else it will not fit on the computer screen without having to scroll side to side.
- If you scan a photo or document and you'll plan on enlarging it to print it, then you should use the maximum resolution at 100% size. This way, you not lose any of the detail when you enlarge it. But, keep in mind that this could be a very large file - perhaps as large as 18 megabytes! So, this would likely be a file that you'd want to immediately burn to CD-Rom, rather than store on your working hard drive.
- If you intend to save this document or photo for posterity consider scanning the document at a high resolution (600-1000 dpi) and 100% size. As with the "print" resolution option, above, you will want to burn this image to a CD or save it to a large external drive, too. You might consider editing the document and adding a white margin below the document and placing a caption that either states the document's origin source citation or the case of photos, the name(s) of the subject(s) and the approximate date of the photo. Consult your graphics editing software to learn how to caption a document.
- Bitmap (.bmp) is the default image format for the pre-XP Windows operating system. It will provide saved images of high quality.
- Tagged Image File Format (.tiff) is also very detailed, and unlike the bitmap file format, it’s supported across most operating systems, including Mac.
- The Joint Photographic Experts Group (.jpeg) format compresses the data somewhat, but is generally sufficient for most uses. This is a "lossy" format, meaning that some data is lost when saving to the .jpeg format. You can set most photo scanning and editing software to save .jpeg files at the least lossy setting.