ISO
Definition
A standardised sensitivity rating for digital sensors; higher ISO values amplify the output and allow lower-light capture but introduce random noise that may mimic surface texture.
- Function
- Sensitivity rating for digital sensors
- High-ISO effect
- Allows lower-light capture
- Trade-off
- Introduces random noise
- Forensic caution
- Noise may mimic surface texture
Common questions
Why does high-ISO noise matter for forensic photography specifically?+
When an image is used to examine fine surface detail such as a tool mark or fabric weave, random sensor noise at high ISO can visually resemble texture that is not actually present, so examiners are trained to keep ISO as low as lighting allows and to note the setting used.
How do forensic photographers compensate for low light without raising ISO excessively?+
They typically favour a longer exposure on a tripod, additional controlled lighting such as flash or continuous lamps, or a wider aperture within depth-of-field limits, reserving high ISO for situations where none of those options is practical.
Related terms
- ABFO No. 2 Scale
- The right-angle L-shaped reference scale with circular targets used in bite mark photography. Its design enables post-capture correction of lens distortion and...
- CCD (Charge-Coupled Device)
- A sensor architecture that transfers accumulated pixel charge across the array to a single output amplifier, producing uniform noise characteristics suitable for...
- CMOS (Complementary Metal-Oxide Semiconductor)
- A sensor architecture with per-pixel amplifiers, enabling fast readout and low power consumption; BSI-CMOS variants now dominate professional forensic cameras.
- Depth of Field (DoF)
- The zone of acceptably sharp focus around the focused plane; controlled by aperture, focal length, and subject distance. Critical for close-up evidence...
- Diffraction Limit
- The aperture threshold below which wave diffraction at the aperture edges degrades resolution more than the narrower aperture improves depth of field....
- Dynamic Range
- The ratio in exposure stops between the brightest recordable highlight and the darkest shadow detail above the noise floor; typically 12-14 stops...
- F-Stop
- The ratio of focal length to aperture diameter, expressed as f/number. Lower numbers mean wider aperture, more light, and shallower depth of...
- Focus Stacking
- A computational technique combining multiple images focused at sequential depths into a single all-in-focus image; used for three-dimensional evidence with relief exceeding...
- Oblique Lighting
- A lighting geometry with the source at 5-30 degrees to the evidence surface, casting long shadows that reveal surface relief. Standard for...
- Ring Flash
- A circular flash tube mounted around the lens that illuminates from all azimuths simultaneously, producing uniform shadowless illumination used for bite-mark and...
- White Balance
- A camera setting that corrects for the colour temperature of the ambient illuminant, ensuring neutral colours render as neutral. Manual white balance...