Exposure Value (EV) vs. ISO Speed Standards
Comparing 2 standards across 11 specifications. 11 key differences identified.
Exposure Value (EV, standardized under ISO 2720) is a logarithmic base-2 scale quantifying combinations of shutter speed and relative aperture that yield identical photographic exposures (EV = log_2(N² / t) at ISO 100). Governs light metering, auto-exposure compensation, dynamic range benchmarks, and the classic 'Sunny 16' outdoor rule.
ISO Speed (standardized under ISO 12232 for digital sensors and ISO 6 / ISO 2240 for film, combining historical American ASA arithmetic and German DIN logarithmic scales) defines the sensitivity of an imaging medium to light. Operating on an arithmetic doubling progression (ISO 100 -> 200 -> 400 -> 800 -> 1600 -> 3200 -> 6400), each step doubles sensitivity, requiring half the exposure time (+1 EV).
Specification Comparison Table
11 Parameters| Parameter / Spec | ||
|---|---|---|
|
Mathematical Formula
|
EV = log₂(N² / t) — where N is f-number and t is shutter speed in seconds (at ISO 100) | — |
|
EV 0 Baseline
|
Aperture f/1.0 with a 1.0-second shutter speed at ISO 100 | — |
|
Sunny 16 Rule (EV 15)
|
Bright direct outdoor sunlight = EV 15 (Set aperture to f/16, shutter speed = 1 / ISO speed, e.g. 1/100s at ISO 100) | — |
|
Typical Real-World EV Benchmarks
|
EV -4: Full moon night sky | EV 4: Candlelight interior | EV 7: Typical home interior | EV 12: Overcast day | EV 15: Sunny beach/snow | — |
|
Auto-Focus Low-Light Rating
|
Modern mirrorless AF sensitivity is rated down to EV -6 to EV -9 (operational in near pitch-black darkness) | — |
|
Dynamic Range Measurement
|
Expressed in EV stops (e.g. 14 EV of sensor dynamic range = a 16,384:1 contrast ratio) | — |
|
Standard Arithmetic Progression
|
— | ISO 50 -> 100 -> 200 -> 400 -> 800 -> 1600 -> 3200 -> 6400 -> 12800 -> 25600 -> 51200 -> 102400 |
|
1/3-Stop Increments
|
— | ISO 100, 125, 160, 200, 250, 320, 400, 500, 640, 800, 1000, 1250, 1600, 2000, 2500, 3200 |
|
Dual Native ISO Architecture
|
— | Two distinct analog gain circuits, switched rather than blended (e.g. Sony A7S III/FX3 in S-Log3: Low Base ISO 640 / High Base ISO 12,800 -- exact pair varies by camera and picture profile) |
|
Base ISO Signal-to-Noise
|
— | Maximum dynamic range and 14+ stops of tonal latitude typically occurs at the camera's lowest native hardware ISO (e.g. ISO 100 or ISO 64 on Nikon D850/Z8) -- dual native ISO sensors are the exception, with a second local peak at their high base ISO |
|
Historical Standard Fusion
|
— | ISO 400/27° fused American ASA 400 (arithmetic) with German DIN 27° (logarithmic) |