My 5/11/08 Missoulian column
I’m finishing up with digital photography this week, and there are two items left to cover: How to prepare images for the Web and suggestions for backing up and preserving digital images.
The first item is preparing images to avoid the common mistake of having too large a file size for efficient display on a Web page. If you don’t put your images on a Web site, you can skip this section – it’s a bit abstract – and move on to image backup and preservation.
If you’ve ever viewed a Web page where the text and layout downloads quickly but the photos are drawn slowly, you’ve come across what I’m talking about. Sometimes images download so slowly you might give up and move on to another Web site. The problem is either the file size – in terms of bytes – or the dimensions of the image being larger than they need to be.
The issue begins with the fact that digital cameras produce images that are much higher quality than what can be displayed on any computer monitor or laptop screen. The reason is images on computer screens are much lower resolution than an image printed on paper. All that extra image quality is useless if the computer screen can’t display it.
In technical terms, there’s no need to save an image at more than 72 dots per inch because a screen can’t display any better. A high-quality photo can be thousands of dots per inch and, as a result, have a much larger file size. All that data has to download to your PC to view the Web page, and the more data there is, the slower the download, even when the image can’t be viewed in better quality than the screen will allow.
The other problem with images on Web pages is using a large photo at a small size. Basically, it’s the same deal as with file size – all the high resolution is wasted when it’s displayed smaller on a Web page.
To properly prepare an image for the Web, you’ll have to hunt around a bit in the features of your image-editing software, either what you bought off the shelf or what came with your camera. Look for a command such as “save for Web” or “save for e-mail” – that will get you on the right track. Check the “Help” menu, too. You’ll be saving the new image as a JPG or a GIF, which are file formats for images used on Web pages. Chances are, your images already are JPGs after being downloaded from your camera.
You want to save the Web image as “low quality,” “screen quality” or something similar. Also, change the image name so you don’t overwrite the original file; you may need the high-quality version in the future.
On a Macintosh with OS X, try Preview, in the Applications/Utilities folder. First, scale the image in the percentage window, then save it as a low-quality JPG. On Windows XP, you can download a tool from Microsoft called the Image Resizing Power Tool that will let you format images for Web sites and e-mail through a right-click menu option. (Download it here). Online photo-editing sites such as Snipshot.com also can help you save images at the correct resolution for display on a Web page.
The next topic, file backups and preservation, is really two different issues. Backups are for short-term safety in case your computer crashes. Preservation could be termed as long-term backup, but also includes other concerns.
A different kind of preservation was a concern with chemical-based photographic film. Plastic and silver-based chemicals will degrade over time and paper prints age, too, unless printed on archival paper. (Digital prints will degrade unless on archival paper, as well).
The thing to remember these days is that the ones and zeros of digital information don’t decay, but the media your images are recorded on do. CDs you burn on your PC can last as little as a few years. And digital file formats and storage methods change. Remember the Betamax vs. VHS battle? CDs are already on the way out, and DVDs are now available in a format called Blu-ray.
I don’t think we’ll have to move our digital photos to new media every 10 years, as USB and Firewire drives will be around for quite some time, but it’s something that libraries and archives have to deal with. They’re investing a lot of time and effort in digital preservation.
For individuals making backups or archiving for preservation, flash drives and memory cards are small and convenient but with a 2 gigabyte capacity can fill up quickly. If you look around, you can find a 250 GB hard drive – 100 or more times the storage space – for about $100, and regular disk drives have a better life span than flash drives.
The issue of most concern for backup or preservation drives is safeguarding them from loss or damage rather than disk crashes or format changes. If you really want a safe place for your data, consider using two disk drives. Put one in a safe-deposit box at a bank or somewhere other than home. At home, keep a duplicate drive in another structure, such as a garage. (If you bring it inside during the winter, let it warm up for a few hours before you plug it in.)
Online backups are another option, but with the amount of disk space images take up, you’re looking at monthly charges and long upload times unless you have a fast connection. The big advantages to online backups, however, are your data is encrypted and spread all over the world on different servers, the reliability is close to 100 percent, and there are no disk drives to mess with. Google “online backups” and you’ll find many different offerings.