The following is a Plus Edition article, written by and copyright by Dick Eastman.
One question that pops up frequently is: “What format should I use to save my files?” The question is often asked about digital pictures. Should they be saved as JPG or PDF or GIF or PNG or TIFF or some other format? Similar questions are often asked about word processing files, although there seem to be fewer options available. I thought I would offer a few suggestions and also tell what works for me.
Today’s technology allows for a selection of image file formats, including JPG, GIF, TIFF, BMP, PSD, RAW, PNG, EPS, PDF, and others in a seemingly endless alphabet soup of abbreviations and acronyms.
You can find many good reasons and bad reasons for selecting any of these file formats. However, from a genealogist’s point of view, there are two significant issues to deal with: image size and image compression.
NOTE: PDF files have unique advantages and disadvantages for both digital pictures and for documents. I will write about PDF separately later in this article.
Image size has been an issue since the first scanned images were stored on a computer, back in the vacuum tube days. In this case, the physical size of the picture is not the issue, but the size of the file you create was very important. That is, the problem revolved around the number of bytes required to store a faithful reproduction of the original image.
Not many years ago, disk drives were expensive. Luckily, that problem is disappearing as the price per byte of storage has plummeted in the past few decades. Prices for one-terabyte disk drives have now dropped to the $50 range, a price undreamed of only a few years ago. It is now cost-effective to store hundreds of thousands of very large digital image files. Prices for disk storage are still dropping nearly every week.
However, file size remains an issue when transferring those files to another computer or when inserting images into a web page. Not everyone uses high-speed, multi-megabyte-per-second Internet connections. Next, even those who do use such high-speed connections find that including very large digital images in a web page results in slow performance. A high-resolution picture also might not display properly inside a web page. Such a picture might fill the entire screen or even “overflow” the screen, leaving no space for text, links, and other information in the web page. Finally, sending a hundred or so old family photographs to a cousin can be a painstaking effort if the files are very large.
Image file size, expressed as the number of bytes, increases with the number of pixels composing an image and the color depth of the pixels. The greater the number of rows and columns, the greater the image resolution and the larger the file. Also, each pixel of an image increases in size when its color depth increases: an 8-bit pixel (1 byte) stores 256 colors, and a 24-bit pixel (3 bytes) stores 16 million colors. Most color images these days are stored as 16-bit or, even better, as 24-bit colors. However, if the original picture is large (perhaps 8-by-10 inches or larger) and is scanned as a high-resolution image, the resultant digital image can be huge.
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