To convert slides into digital format, you have four major options:
Slide DuplicatorIf you own a good digital SLR (single lens reflex) camera, a slide duplicator, or duper, offers a good, inexpensive option for digitizing your slides. A slide duplicator attaches to your DSLR camera's in place of the lens, using a T-mount adapter ring. The other end of the duper is a sliding gate that holds two slides. The duper also has an internal lens, with a fixed aperture and focusing distance, that focuses the slide's image onto your DSLR's imaging plane so that you can then take a picture of the slide.
While inexpensive and easy to use (they require no electricity or a computer since you can take the pictures directly onto your camera's flash card), dupers do not offer the digital quality you can get from a flatbed or film scanner. In most cases you'll find that some image cropping is unavoidable. Most digital cameras also don't offer the dynamic range (the amount of gradation between light and dark in the photo) of a scanner, which can affect the photo's shadow detail. Scanners generally offer better resolution (a 3200 optical dpi scanner is about equivalent to a 12 megapixel digital camera) as well, so if you want to print larger photos from your slides, this may be a deal breaker.
Flatbed ScannerMany traditional flatbed scanners do a good job at slide scanning as well. Look for a scanner that is designed to scan negatives and slides in addition to traditional paper photos and documents. The optical (not digital) resolution should be at least 2400 dpi or greater. Many flatbed scanners require an extra transparency adapter attachment for scanning slides - sometimes it comes with the scanner, and sometimes you have to buy it separately. Good bundled scanning software is also a must, to give you control over the final results, although Hamrick's VueScan offers an excellent alternative and works with most flatbed scanners. Read user and editorial reviews to find a flatbed scanner that handles slides well before you buy.
Dedicated Film ScannerFrom an image quality standpoint, the best method for digitizing your slides is to use a high resolution dedicated film/slide scanner. They can be fairly expensive, so probably not the best option unless you literally have thousands of slides to scan. Dedicated film scanners do, however, offer excellent resolution, and the control they offer over the final images is something you generally don't have when you opt for a professional scanning service.
Professional Photo ShopIf you don't have too many slides, or if you're not very comfortable with computers and software, then your best bet is probably to opt for a professional service to scan your slides for you. Many such services can be found on the Internet, but you may find more peace of mind by checking with local photo labs. Definitely shop around because pricing and quality control vary widely. Do be sure to ask whether the photo shop cleans and scans each slide individually. If they batch scan, you probably won't be happy with the quality.
Tips for Scanning SlidesThe trick to getting good digital scans of your slides is to start with clean slides. Dust both sides of each slide off with a quick hit of compressed air and be careful not to touch the emulsion. Make sure your computer is fairly new with a fast processor and plenty of memory and hard drive space to store all of the digital images. A plug-in external hard drive is a good option when scanning slides or photos. I would highly recommend that you scan directly into a good photo organization/editing program such as Photoshop Elements, which can drastically cut down on the time spent scanning as you can save naming the files, cropping, rotating, etc. for later once the images are all on your computer in the organizer.
After scanning, back up your new digital files onto DVDs - and make extra copies to share with your family members!