Exposure Triangle
Definition
Aperture, shutter speed and ISO. The three variables a photographer balances to produce a correctly-exposed image.
- Components
- Aperture, shutter speed, ISO
- Field
- Forensic photography exposure control
- Trade-off
- Changing one variable requires adjusting another to hold exposure
Common questions
Why does the exposure triangle matter specifically for forensic photography?+
Forensic images must be evidentially reliable and reproducible, so the photographer chooses aperture, shutter speed and ISO deliberately, for depth of field on a fingerprint or freezing motion at a scene, rather than relying on automatic modes that obscure how the image was produced.
What happens to image quality if ISO is raised to compensate for a fast shutter speed in low light?+
Higher ISO amplifies sensor noise, which can degrade fine detail such as toolmark striae or trace evidence texture, so forensic photographers generally prefer widening the aperture or adding lighting before raising ISO.
Related terms
- DSLR vs Mirrorless
- DSLR uses a mirror and optical viewfinder; mirrorless uses an electronic viewfinder. Modern Indian SOCO kits include both; mirrorless is increasingly the...
- Lens Classes
- Wide-angle (under 35mm full-frame) for overviews, normal (50mm) for mid-range, macro (1:1 or closer) for close-ups, telephoto for surveillance and exterior contexts.
- Photo Log
- The contemporaneous record tying each forensic image to its capture time, location, equipment, exposure settings, and subject description. The primary chain-of-custody document...
- Three-Shot Rule
- The convention that every piece of evidence is photographed at three distances: overview (scene-context), mid-range (position relative to landmark), and close-up (with...