Multimedia Forensics: UV, IR and Alternate Light Photography

UGC-NET Forensic Science Paper II Unit VI drill on the application of ultraviolet, infrared and alternate light source imaging in forensic casework. Items run from the hardware of UV photography (Schott UG-11 UV-pass filter, quartz lens, modified DSLR with the IR-cut filter removed) through the physics of reflected UV imaging versus fluorescence photography (excitation-barrier filter pair, Stokes shift, emission spectrum capture), and into IR photography with Wratten 87 and 89B filters. Alternate light source technology covers tunable LED ALS units such as the Crime-lite ML2 and Polilight Flare across the 350 to 700 nm range, bandpass versus longpass barrier filter selection, and the optical density rating that controls stray-light leakage. Application questions cover bite-mark documentation under reflected UV before and after injury development, body-fluid screening (semen, saliva and urine fluorescence), gunshot residue and powder-fouling imaging on dark fabrics under IR, and ink differentiation by IR reflectography on questioned documents. Fluorescence physics questions test the Stokes shift, excitation and emission spectra, the optimal barrier filter placement on the emission curve, and fluorescence quenching by substrate interference. Indian context anchors include CFSL questioned-document UV and IR imaging protocol, the standard UV-VIS-IR photography sequence in document examination, and the admissibility of expert scientific reports under Section 45 Indian Evidence Act 1872 (now Section 39 Bharatiya Sakshya Adhiniyam 2023).

Designed for MSc and BSc forensic science students sitting UGC-NET Paper II, NFSU MSc entrance, and CFSL Multimedia and Document Division recruitment tests. The item set also serves State FSL examiners refreshing filter-selection and ALS-protocol knowledge before report-writing.

Topics covered:

• Reflected UV imaging: UG-11 filter, quartz lens, modified DSLR
• Fluorescence photography: excitation-barrier pair, Stokes shift, emission capture
• IR photography: Wratten 87 and 89B filters, modified sensor
• ALS technology: tunable 350 to 700 nm, Crime-lite, Polilight, barrier filter OD
• Body fluid screening: semen, saliva and urine fluorescence under ALS
• Bite mark documentation: 1:1 scale UV photography sequence
• Ink differentiation: IR reflectography on questioned documents
• Indian CFSL practice: UV-VIS-IR sequence, BSA 2023 Section 39 admissibility

Near-twin distractors test whether you can separate reflected UV from fluorescence, Wratten 87 from 89B, and longpass from bandpass barrier roles without collapsing the concepts. Allow 30 minutes.