Perpendicular Camera Alignment
Definition
The requirement that the camera lens be directly above the impression centre with the sensor plane parallel to the impression plane; prevents perspective distortion that would invalidate size comparison.
- Requirement 1
- Lens positioned directly above impression centre
- Requirement 2
- Sensor plane parallel to the impression plane
- Purpose
- Prevent perspective distortion
- Field
- Impression evidence photography
Common questions
What goes wrong if the camera is even slightly off-axis when photographing a footprint or tyre mark?+
An angled shot stretches or compresses dimensions unevenly across the frame, so size measurements taken from the photograph, and any scaled comparison to a known standard or suspect item, become inaccurate.
How do photographers verify perpendicular alignment in the field without lab equipment?+
A bubble level mounted on the camera or a tripod head, combined with a scale placed in the same plane as the impression, helps confirm and later verify the alignment was correct when the image is reviewed.
Why is a scale placed alongside the impression still necessary even with perfect alignment?+
Perpendicular alignment removes distortion, but the photograph still needs a reference scale in the same plane to allow accurate size measurement and later one-to-one comparison prints, since the image alone carries no absolute scale.
Related terms
- Class Characteristics (Footwear)
- The manufactured outsole design features shared by all examples of a specific shoe model: tread pattern, size, shape, and logo placement.
- Dental Stone
- A gypsum-based casting material harder and finer than plaster of Paris. Preferred for forensic 3-D casts because it captures detail at the...
- ESLA (Electrostatic Dust-Print Lifter)
- A device that applies a high-voltage static field to a metallised film, attracting dust particles from a footwear impression on a hard...
- R V. Mohan (1994) + White Burgess Langille Inman (2015)
- Canadian Supreme Court framework for forensic-expert admissibility: Mohan sets relevance + necessity + qualification + no exclusionary rule; White Burgess adds an...
- Randomly Acquired Characteristics (RACs)
- Post-manufacture features (cuts, gouges, embedded material, crack patterns) unique to a specific shoe sole or tyre; the highest-level individualising features in impression...
- SICAR (Shoeprint Image Capture and Retrieval)
- FBI and Foster and Freeman (UK) outsole design database used for class-characteristic database searches; referenced in US, UK, Australian, and Canadian forensic...
- Snow-Print Wax
- A spray wax applied in thin coats to snow impressions before casting to provide a thermal barrier, allowing Dental Stone casting without...
- Subclass Characteristics (Footwear)
- Features shared by a subset of shoes from the same mould or production batch; may mimic individual characteristics if not properly distinguished.
- SWGTREAD
- Scientific Working Group for Shoeprint and Tire Tread Evidence; US body that developed the dominant guidelines for footwear and tyre-mark examination, class-subclass-individual...
- Tracking Evidence (TE) Database
- FBI database of tyre tread design patterns, used for class-characteristic identification in tyre-mark cases; accessible to partner agencies internationally.
- Treadmate
- RCMP database of outsole designs for footwear comparison, used by Canadian forensic laboratories and accessible to partner agencies.