F-Stop
Definition
The ratio of focal length to aperture diameter, expressed as f/number. Lower numbers mean wider aperture, more light, and shallower depth of field.
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...
- 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...
- ISO
- A standardised sensitivity rating for digital sensors; higher ISO values amplify the output and allow lower-light capture but introduce random noise that...
- 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...
Explained in
- Forensic Photography: FundamentalsThe ratio of focal length to aperture diameter, expressed as f/number. Lower numbers mean wider aperture, more light, and shallower depth of field.