Transmitted-Light Photography
Definition
Light passed through the paper from behind to reveal watermarks, paper-fibre disturbance, security threads, erasures and chemical thinning.
- Method
- Light passed through the paper from behind, then photographed
- Reveals
- Watermarks, fibre disturbance, security threads, erasures, thinning
- Use case
- Permanent documentation of features seen under transmitted light
- Field
- Photographic and mechanical document reproduction
Common questions
Why photograph a transmitted-light finding rather than just describe it in a report?+
A photograph preserves the exact brightness pattern for later comparison, peer review, or court presentation, whereas a written description cannot reproduce the visual detail an examiner or fact-finder needs to independently assess.
What camera setup does transmitted-light photography typically require?+
A light source positioned behind or beneath the document, with the document itself between the light and the camera, so the lens captures the light that passes through the paper rather than light reflected off its surface.
Related terms
- ESDA
- Electrostatic Detection Apparatus; detects latent indentations in paper by charging the surface and cascading toner particles, revealing tracing stylus pressure and writing...
- Inkjet Printing
- Non-impact printing that sprays liquid ink droplets onto paper. Two main technologies: thermal (HP, Canon, bubble-jet) and piezoelectric (Epson).
- IR Luminescence
- Emission of near-infrared radiation by ink dye molecules when excited by visible light; different ink formulations luminesce at different intensities, allowing differentiation...
- MIC / Yellow Tracking Dots
- Machine Identification Code: faint yellow micro-dots printed by many colour laser printers and copiers on every page, encoding serial number and timestamp....
- Oblique-Light Photography
- Photography of a document surface using illumination at a low angle (10 to 15 degrees from the paper plane), which casts shadows...
- Photographic Reproduction
- Lab-side imaging of a questioned document using controlled lighting (oblique, transmitted, coaxial), filters and wavelengths from UV through visible to IR, to...
- VSC-8000
- Video Spectral Comparator by Foster + Freeman, the standard QD instrument in CFSL and GEQD labs, with broadband visible, UV (254, 365...
- Xerography
- Dry electrophotographic process invented by Chester Carlson (1938). Photoconductive drum is charged, exposed to image, dusted with toner, transferred to paper and...