Scanners are cheap, easy to use for photos

September 14, 1998|By MIKE HIMOWITZ

I've written a lot about digital photography lately because I think it's great technology. But several readers have written asking whether a scanner isn't a better deal than a digital camera.

Their argument: You can always use a scanner to digitize a photograph, but you can't use a digital camera to get other kinds of printed documents in your computer. It's a good point.

At the time when digital cameras are just becoming inexpensive enough for ordinary consumers to consider buying them - $600 to $800 for respectable images - the price of scanners has dropped through the floor.

For less than $200 you can pick up an excellent scanner, and you'll find acceptable quality in units that sell for as little as $80. Most of these models hook up to your computer's printer port (you plug your printer into a pass-through port on the scanner), although if you have a relatively new computer, you might want to look for a model that plugs into your PC's universal serial bus.

What does a scanner do and how does it work? Well, a scanner is actually digital camera of sorts. It takes an image (a photo, diagram or printed page) and turns it into a pattern of zillions of little dots that can be stored as digital ones and zeros in a file on your computer's hard disk.

With the right software, you can view and edit those images, and use them in other documents. You may want to include a photo of the boss in a company newsletter or post a picture of the family on your Web site. You can use your modem to fax a scanned letter to a business associate. With optical character recognition (OCR) software, you can turn the image of a printed page into text that you can edit in a word processor, spreadsheet or desktop publishing program. This can save an enormous amount of retyping.

There are two basic types of scanners. Flatbed models work like copiers - you put a photo or sheet of paper on a glass platform and a scanning head passes underneath it, turning the image into dots. Sheet-fed scanners use rollers to pass your image under a stationary scanning head.

Flatbeds produce better scans of photographic images, and they can be used to scan pages from books, magazines and other bound documents. Sheet-fed scanners take up less space, and they're more convenient for scanning in batches of documents for faxing or processing by OCR software. You can buy sheet feeders for better-quality flatbed scanners, but they often cost far more than the scanner itself.

What makes one scanner better than another? Two of the most common measures are resolution and pixel depth.

Resolution refers to the number of dots a scanner can make of your image. The more dots it can resolve, the more detailed the image. Resolution is measured in dots per inch (dpi), horizontally and vertically. A 600-by-300 dpi scanner can resolve 600 horizontal dots per inch and 300 vertical dots. A scanner's

optical resolution - the important number - refers to the number of dots the hardware can produce unaided. Most scanners can post higher numbers by using software to artificially enhance resolution, but it's better to buy hardware that can do the job.

The problem is that as resolution goes up, so does the size of the file your image produces. For example, a 600-dot scan of an 8 by 10 photograph can eat up 86 megabytes of disk space - it's far too large for all but professional graphics computers to handle. To produce good photographs for most purposes, you probably won't need more than 300-to 400-dpi resolution.

Pixel depth refers to the amount of data used to store color and intensity data for each dot your scanner records. Today's run-of-the-mill scanners record 24 bits per pixel - enough for 16 million discrete colors, which is about all the human eye can discern. Better scanners use 30 bits per pixel and use the extra information to help resolve detail in shadows and other hard-to-scan areas of your image.

What's harder to determine is the scanner's mechanical quality - the precision of the scanner head or roller movement, as well as the sophistication of the electronics that process the image. Some can scan a photo in a few seconds - others require minutes. For that kind of information, it's best to read hardware reviews, ask other scanner owners or try a few models out yourself.

Software is also important. Most scanners use basic "driver" software that meets an industry standard called TWAIN. This allows you to scan images directly into photo editing or graphics programs. When a TWAIN scanner driver is installed, a new function called "acquire" will appear on the File Menu of every program that supports scanning.

But scanner software varies widely in quality and ease of use. Some scanner drivers will allow you to scan an image at a larger or smaller size than the original - a major convenience. Others require you to scan it at full size and change the dimensions using photo editing software, which can degrade the quality of the final image.

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