The better way to scan 35mm slides into a computer is to use a slide scanner. Slide scanners give the photographer effective control over each slide image. The other way, using a flatbed scanner, also works relatively well, especially if a lot of slides need scanning. If you want top-grade slide scans, you need a slide scanner. For most people, however, who plan to transfer those old vacation and family photos to CDs, the flatbed will shorten scanning times and produce good images.
Start the process by cleaning the slides, particularly if they have been in a closet for many years. The simplest and safest way to do this is to use a can of compressed air with a long nozzle. Electronics and photo stores sell compressed air, and you can find it online, too. Hold the slide up to a light and use the compressed air on both sides of the image. If your slides have glass or plastic covers over the images, start with compressed air, but then use a lint-free cloth to wipe them. This should be done carefully to avoid scratches.
Take off the pressure pad that adheres to the top inside area of the flatbed scanner lid. This most often will snap or slide out. The pressure plate is there to hold prints flat on the scanning glass, but it also covers the light in the lid of a transparency scanner. If the lid does not come out, check your scanner manual to make sure you are doing it correctly and to make certain your flatbed scanner is designed to scan transparencies such as slides.
Put the slides flat and square on the scanning glass. If your scanner came with 35mm slide templates, you can snap the mounted slides into these. While these make certain the slides scan evenly and squarely, they will cut down on the number of slides you can scan at once. When the slides are secure, gently close the lid and turn on the scanner.
Open the scanning software on your computer, but do not use the default settings. Most scanners will set the default resolution or final quality at a relatively low number such as 200 or 300 dots per inch (dpi). The manufacturer has decided a default based on a balance between quality and scanning speed. These slides must be important to you, or you would not bother scanning them, so you need to set a much higher resolution. This becomes especially important if you want good-sized enlargements later on. Some flatbeds go up to 9,600 dpi or more, and while this will make the scans take longer, it will produce much better quality.
Scan the slides, individually or as a batch, then save the files to an external hard drive, particularly if you plan to scan a lot of images. Open your photo-editing software and make any corrections you need to make. Old slides, for example, may display colour fading, which you can correct in the software. You also can repair spots, dust and scratches this way. Save the new version of your images in a separate folder under different names than those attached to the raw-scanned images. If you want top-quality but disc-space-hog images, you will need to save them in TIFF format. If you want more images on each disc, save them in JPEG.
Open your CD burning software and start your CD burner. Drag or import the digital slide images into the software, depending on how your specific software works. Remember that you can only get approximately 700 megabytes of data on one CD. You will get far more images in JPEG format than in TIFF, but you will lose quality because JPEGs are compressed files. Set the parameters for the CD and start the burning process.
Some "transparency" scanners have a hole in the cover and a motor drive unit into which you can feed negative strips. You cannot put mounted slides in the scanner this way, so you will need a different flatbed scanner. However, if your slides are not mounted and remain in uncut strips of film, you can use this type of scanner.