Digital Pictures 101: Scanning Resolution
Do you have old family photographs that you’d like to bring into the 21st Century? Imagine the fun and excitement that would come from being able to share such treasures with your family, using today’s digital computer tools and networks.
To do this, you’ll need a scanner. But fear not; these days, a good quality scanner can be had for as little as $100. (This is fantastic, given that my first scanner, purchased in 1995, cost $1000.00!)
In order to use your scanner, you’ll need to understand “resolution,” and you’re in luck, because that’s what this installment of Digital Pictures 101 is all about.
Images scanned at low resolution (like the one on the left) often appear relatively clear and crisp when viewed as very small images or on a computer screen. Unfortunately, things aren’t always as they seem.The reality is that printing images that have been scanned at such low resolutions will result in fuzzy faces and much frustration—print out a 5x7 copy of the photo above and all you’ll get is a sea of little gray squares (like the large image above).
So what is the best resolution to use for scanning family photographs?
Here’s a simple rule of thumb — if you are scanning an image to make a same-size printed copy of that image, scan it at 300 dots per inch (dpi). However, beyond same-sized copies, determining optimal scanning resolution gets a lot more complicated. One trick is to have in mind the final device or medium that will display your image. (See Table 1, below)
Table 1 - Suggested Resolution based on Final Destination
This works great when you wish to reproduce the item you are scanning at about the same size as the original being scanned. However, it all falls apart when you scan a tiny picture that you wish to display much larger. However, a better way of choosing the correct resolution is to have a target uncompressed file size in mind.I like to think of my final destination medium as a storage device. Do I plan to view the image on a still TV, a computer screen, or a high-definition screen? Is the largest image I plan to print 5x7, or will I be printing a 10x14? And yes, a piece of paper is a storage medium—it holds 19 MB of color information at 300 dots per inch. Take a look at the following table:
Table 2 - Suggested Resolution Based on File Size of Popular Media*
It's ironic that just when we're starting to get used to the metric system, where "kilo" means 1,000, and "mega" means 1,000,000, those computer geniuses/ hackers/ nerds go and turn everything upside down!After looking over the file size requirements listed in Table 2, you may be thinking, “Are you crazy? If I scan my photographs at the high resolutions that are needed to produce quality print images, it’s going to take up a huge amount of memory space on my computer! Where am I going to store all that image data?”
The first part of the answer is compression — which greatly reduces the amount of space needed to store a high resolution picture, albeit at some cost to quality. Compression will be the subject of the next installment of Digital Pictures 101.
The second part of the answer to the question of where to store all that image data is — Family Photoloom™ of course — the best place on the Internet to store and share your photo-history!
Coming Soon: Digital Pictures 101: Compression — A brief comparison of file types (TIFF, BMP, JPEG, and GIF); tips on scanning documents, including using digital cameras.
* Math Wiz Notes for Table 2
• It takes 3 bytes to store a color pixel (one byte for each of red, green, blue).
• There are 1024 bytes in a KB (read Kilobyte)
• There are 1,048,576 (1024x1024) bytes in a MB (read Megabyte)
• And a Gigabyte? 1GB = 1,073,741,824 bytes! (1024x1024x1024)
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Excerpted from “No More Fuzzy Faces: The Secrets of Digitizing Family History”, originally presented by Scott Huskey at the BYU Family History and Genealogy Conference, Provo, Utah, March 2008.
Thank you so much for the info. I asked Laurie this the other day. On my more energetic days, I want to scan in all my old photos and wanted to do the best job without boggin down the computer by doing too much resolution. This gives me a good idea of what I need.