A small glossary of photo restoration

Restoration guides, scanner manuals and conservators all speak a compact dialect — emulsion, halftone, archival, DPI — that assumes you grew up in a darkroom. This glossary translates the terms you will actually meet while rescuing a family archive, in plain language and without the chemistry lecture. Each definition sticks to what the word means for your photos in practice.

How to use these terms

You do not need this vocabulary to restore a photo — upload a scan and the work happens regardless. It earns its keep when you read about your photos elsewhere: dating a print by its process, understanding why the scanner asks about DPI and descreening, or following a conservator’s advice without translating every second word.

The definitions favor the family-archive context over technical completeness. Where a term means several things in photography at large, we give the meaning you will meet while scanning and restoring old prints.

Colorization: Adding reconstructed color to a black-and-white photograph. The original never recorded color, so colorization is an informed inference from texture and context — plausible rather than documentary, and best treated as an interpretation of the image.
Upscaling: Enlarging a digital image beyond its original pixel size while reconstructing detail, so a small print or coarse scan can be printed larger without turning into visible blocks. Modern upscaling generates plausible fine detail rather than just stretching pixels.
DPI: Dots per inch — the resolution setting when scanning (strictly PPI, pixels per inch, but scanner software says DPI). 600 DPI is a sound choice for small prints; below 300 the scan starts discarding detail that no later step can recover.
Film grain: The fine, sand-like texture of film photographs, formed by the clumps of silver (or dye) that make up the image. Grain is part of the photograph’s character, not damage — good restoration cleans scratches without steamrolling grain into plastic smoothness.
Sepia: The warm brown tone of many old photographs. Often it was applied deliberately — sepia-toned prints resisted fading better and the color was fashionable — though similar warmth can also creep in as paper and image age.
Silver gelatin print: The standard black-and-white photographic print of the twentieth century: paper coated with gelatin holding light-sensitive silver. If your family archive has black-and-white prints from roughly the 1910s to the 1980s, they are almost certainly silver gelatin.
Vignette: Darkening or fading toward the corners and edges of an image. In old portraits it was often deliberate — a soft oval fade around the sitter was studio fashion; in snapshots it can simply be the lens. Restoration can keep or remove it, and taste decides.
Negative: The developed film original in which tones are inverted — dark is light and light is dark. Prints were made from negatives, and a surviving negative usually holds more detail than any print made from it, which makes negatives the best scanning source when you have them.
Contact sheet: A print made by laying film strips directly on photographic paper, producing one small positive of every frame on the roll. Photographers used contact sheets to choose which frames to enlarge; finding one tells you more frames existed than the prints you inherited.
Emulsion: The thin image-bearing coating on photographic paper and film — gelatin holding the silver or dyes that form the picture. It is the fragile layer: scratches, cracks along folds and water damage are all injuries to the emulsion rather than to the paper beneath.
Halftone: The printing technique behind photos in newspapers and books: the image is broken into a grid of dots whose sizes simulate continuous tone. Scanned halftones tend to produce moiré interference patterns, and restoring one means rebuilding smooth tone from the dots.
Archival scan: A digitization made to preservation standards rather than for quick sharing: high resolution, no automatic corrections, saved in a lossless or minimally compressed format, and backed up in more than one place. The scan you make once so nobody has to rescan a fading print later.