Scanning Negatives and Transparencies
Before starting a scanning project, you need to make decisions regarding image file format, image resolution, color mode, and color bit depth for your scanning software. Also see the "Best Practices" subheading if you need extra input in making archival digital files for your slides, negatives, or transparencies.
Image File Format
- Photoshop: Proprietary software uses layers. Not recommended for archival image use.
- RAW: Proprietary software, camera specific, lossless compression, nondestructive editing. Proprietary software image format not recommended for archival image use.
- TIFF, lossless compression. Recommended for archival image use.
- JPEG, lossy compression. Not recommended for archival image use. Never use a file format that is lossy for archival images.
- Pixel Resolution along width of image
- Pixel Resolution along height of image
- Spatial Resolution or pixels per inch
- Color Mode: RGB, CMYK, Grayscale, Bitmap. Use RGB and Grayscale for archival images.
- Bit depth, color depth, or bits per pixel. Higher color depth gives a broader range of distinct colors but also results in a much larger file and cannot be used by some software.
Image File Format: TIFF, lossless compression for archival image files. JPEG and PDF derivatives can be created from the TIFFs for web viewing.
Color Mode and bit depth: 24-bit RGB regardless of whether the image was photographed in color or black and white. More gray values will be captured when using 24-bit RGB.
Pixels: 5,000-6,000 pixels on the long side of the image
Spatial Resolution or pixels per inch: It is important to note that for best resolution, the ppi setting should be an integer of the optical resolution of the scanner. For example, if the optical resolution of your scanner is 6400 ppi, the resolution setting should be 6400, 3200, 1600, 1280, 800, 400 ppi and so on. With an optical resolution of 4800 ppi, the resolution setting should be 4800, 2400, 1600, 1200, 960, 800, 600, 480 and 400 ppi. Do not scan at a higher resolution than your scanner's optical resolution. It will result in a bloated file size and the image quality will not be any better than it would have been at the scanner optical resolution.
Never handle film with your bare hands. Your hands have oils on them, which will cause permanent damage to the film. Finger oils interact with the emulsion and base of the film.
Marriott Library Digital Operations uses Kinetronics anti-static gloves. Whatever you use, make sure the chemistry of the gloves will not leave a residue on the film or shed fibers. The only exception to not using gloves is if you will only be handling the cardboard, plastic or metal of the transparency mount and you do not touch the film. Periodically wash gloves, rinse well and air dry.
If the slide or transparency is mounted in a glass mount, it is best if you remove the glass before scanning an archival file.
Reasons for removal of glass before scanning
- You need to know which side of the film is the emulsion side for proper insertion into the scanner and to avoid a reversed image.
- Dirt, dust and residues inside the glass mount lead to a substandard scan.
- An interaction between the base (gloss) side of the film and the glass of the mount may result in Newton Rings (ring-shaped stripe pattern) that will show up in your scan.
- Anti-Newton glass in a slide mount slightly obscures the image and the pebbled surface can be seen in a high-resolution scan.
- Sometimes the paper holder inside a full glass mount cuts off part of the image.