Q I have lots of great colour slides which I have collected over the years. I would now like to put them into a computer and possibly on the Net, so how do I scan slides/transparencies and turn them into electronic files?

A There are lots of good reasons to digitise your slides and photos, and the possibilities are endless. You can enlarge and reduce images, manipulate them in various ways, and add special effects. You can also e-mail snapshots to family and friends, illustrate your web site, and add your personal touch to invitations, cards, calendars, T-shirts, newsletters and presentations. The easiest way to get your slides into your computer is to scan them. You can do this in three different ways.

Use a flatbed scanner. This is the most popular type of scanner and is commonly used for scanning flat artwork such as photos and printed pages. Flatbed scanners are usually capable of scanning at resolutions of 300, 600 or 1200 dots per inch (dpi), and work by bouncing light off the original document. To successfully scan slides, x-rays and other transparent documents, though, a scanner has to be able to pass light through the image rather than reflect light off it. A flatbed scanner can do this using a transparency unit with a separate light source, and many scanner manufacturers offer these units as optional extras. ThereÆs not much point in trying to scan a slide directly on a flatbed scanner, as the results will be poor, even at higher resolutions.

Use a dedicated slide scanner. These scanners are usually much smaller and more expensive than flatbed scanners and can only be used for scanning slides. They produce very high quality scans and support resolutions of between 1950dpi and 2700dpi. Polaroid, Nikon, Minolta, Konica and Kodak all make slide scanners.

Use a professional photo lab. If you have many slides to digitise you might consider taking them to a photo lab that produces PhotoCDs. At the lab, your slides are scanned with a high-resolution scanner, and the images are then transferred to a CD. A PhotoCD can be read on any computer with a CD-ROM drive, and usually comes with a printed index that shows thumbnail pictures of the images on the CD. Your original slides should also be returned to you. At a Kodak Image Express shop you can choose to have your pictures put onto either a FlashPix CD, which holds approximately 400 low-resolution images, or a PhotoCD, which holds approximately 200 high-resolution images. The process takes five days for both types of CDs, and you need to have a minimum of 20 slides. A FlashPix CD currently costs around $20 for the CD and 90 cents for each of your slides; a PhotoCD costs $20 for the CD and $2.50 for each slide.

If you need instant scans, youÆll be better off with your own scanner, and if you already have a flatbed scanner you might consider buying a transparency unit. A high quality flatbed scanner outfitted with a transparency unit should give you more than adequate results. Bear in mind that images for the web donÆt need to be scanned at resolutions any higher than 70-100dpi, as the quality of the on-screen image wonÆt improve significantly at higher resolutions. Also, lower resolution scans will result in smaller files that will download quickly and make your web page load faster. A dedicated slide scanner is expensive, but great if you want to scan only photographic slides or transparencies. They are a good choice if you need to make high quality scans of a large number of slides. If you donÆt need digital images urgently, or if you donÆt already have a scanner and donÆt want to get one, your best bet would probably be to get a photo lab to do all the work for you. The process is relatively inexpensive, the results are excellent, and a PhotoCD is a good way to archive your pictures.