Scanning slides requires one of three types of scanners---a dedicated film scanner, a flatbed scanner with a slide scanning adapter or a home scanning unit. Most scanners come with scanning software. The software determines the digital characteristics of the scanned image---resolution, bit depth and output size. Capturing a good scan from a slide requires patience, an understanding of the equipment and knowledge of the software used.

Clean

Clean the slides before the scan. Most slides not protected in glass slide mounts have some residue or dust on them. Use a blower (the kind for cleaning a digital camera sensor works well) to gently blow the dust from the slides. Always remember to hold the slides by the mount. Touching film with fingers leaves oil residue from the body on the film. If this happens or if the slides have a lot of dirt on the surface, use a film cleaner. Follow the manufacturer's directions for cleaning the slide. Some cleaners have better spot drying action than others. A cleaner that contains a wetting agent helps film dry uniformly and reduces the risk of spots and streaks.

Preview

Preview the slide to determine the best output options. Insert the slide into the scanner and open the software. Most software platforms offer a preview function. The preview function allows the user to adjust various aspects of the imported slide, including resolution, bit depth, color, hue and saturation and output size. Set the parameters according to the desired final image size and quality. Higher resolution and greater bit-depth settings create larger file sizes. Make the required adjustments and press the preview function. When viewed, if the preview image does not match the desired results, readjust the image characteristics and preview again. Scan the slide once satisfied with the preview's output.

Scan

Scan techniques vary depending on the type of scanner used. All require a USB, Firewire or serial port (for older scanners) connection to the computer. Amateur home scanners require very little interaction to achieve decent scan results. Typically the user inserts the slide into the dedicated carrier and presses a button to import the image into the computer using the dedicated software. Flatbed scanners have greater versatility and higher file output. Flatbed scanners require a slide mask to perform slide scans. The user places the slide onto the scanner's bed within the frame of the mask and, using the desired software (Adobe Photoshop, ArcSoft, Corel Draw), imports the image into the computer. Dedicated film scanners act like the amateur scanners except they have greater scanning options and higher-quality output. Use the desired software to adjust the image input to achieve the desired results.

Source:

HP.com: Scan photo slides