Film & darkroom
How three colour records become one colour-negative image
Layered emulsions record different parts of the light spectrum.
A single-frame booth camera can make a colour negative with no electronic sensor. Understanding the separate colour records helps explain why processing and scanning affect hue as well as brightness.
Capture is layered
Colour-negative film contains multiple emulsion layers designed to respond to different portions of visible light. The resulting records do not simply store finished red, green and blue pixels; processing forms dye images whose relationships are interpreted during printing or scanning.
Evidence: Manufacturer technical workbook
Conversion interprets the negative
A scanner measures transmitted light through the negative and software inverts and balances the resulting records. Because the records and film base are not neutral, a general-purpose positive-photo setting can produce a strong cast. Select a negative workflow and preserve an unaltered master scan.
Evidence: Scanner manufacturer manual
Diagnose colour one stage at a time
Compare the negative on a light source, a raw scan and the converted positive. If the cast first appears after conversion, inspect the scanner profile and inversion settings. If colour varies along the strip, check the capture light and processing record before applying a frame-by-frame correction.
Sources & further reading
Sources for the specific facts and product descriptions above. Our worked examples, interpretations and practical suggestions are original editorial guidance.
- Eastman Kodak, Basic Photographic Sensitometry WorkbookManufacturer technical workbook
- Epson, Film Scanning ProblemsScanner manufacturer manual