Film & darkroom
Tell a film-surface scratch from a mark in the image
The location and behaviour of a line can narrow the diagnosis.
Scratches may appear as bright or dark lines depending on where they sit and how light passes through the negative. A scan is useful evidence, but the original strip should remain the reference.
Check the physical strip
Inspect the negative under reflected and transmitted light with magnification. A surface scratch can catch light differently from a feature recorded in the scene. Note whether it crosses the image boundary, repeats at a fixed transport position or appears on several adjacent frames.
Evidence: Manufacturer guidance
Avoid over-reading scan polarity
A scratch on the emulsion side can reduce transmitted density, while a mark on the base side may behave differently. Inversion can swap the apparent light-dark direction. Compare the un-inverted negative and a scan before describing a line as white or black damage.
Preserve the original evidence
Do not scrape or polish a negative to test the mark. Save an unaltered scan and record the film stock, scanner orientation and frame location. For an important family or historic strip, ask a qualified lab or conservator to assess whether cleaning or repair is appropriate.
Sources & further reading
Sources for the specific facts and product descriptions above. Our worked examples, interpretations and practical suggestions are original editorial guidance.
- ILFORD PHOTO — common film processing problemsManufacturer guidance