Exposure Value (EV) vs. F-Stop Scale
Comparing 2 standards across 12 specifications. 12 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.
The F-Stop Scale is a standardized geometric progression of lens focal ratios (N = f / D, where f is focal length and D is entrance pupil diameter) governed by powers of √2 ≈ 1.4142. Advancing one full stop (e.g. from f/2.8 to f/4.0) halves the cross-sectional area of the optical entrance pupil, cutting light transmission precisely in half (-1 EV).
Specification Comparison Table
12 Parameters| Parameter / Spec | ||
|---|---|---|
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Mathematical Formula
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EV = log₂(N² / t) — where N is f-number and t is shutter speed in seconds (at ISO 100) | — |
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EV 0 Baseline
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Aperture f/1.0 with a 1.0-second shutter speed at ISO 100 | — |
|
Sunny 16 Rule (EV 15)
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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
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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
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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) | — |
|
Mathematical Definition
|
— | F-Number N = Focal Length (f) / Entrance Pupil Diameter (D) |
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Geometric Progression Factor
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— | Powers of √2 (~1.41421356...): √2⁰=1.0, √2¹=1.4, √2²=2.0, √2³=2.8, √2⁴=4.0, √2⁵=5.6, √2⁶=8.0, √2⁷=11.3, √2⁸=16.0, √2⁹=22.6 |
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Standard Full-Stop Scale
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— | f/1.0 -> f/1.4 -> f/2.0 -> f/2.8 -> f/4.0 -> f/5.6 -> f/8.0 -> f/11 -> f/16 -> f/22 -> f/32 |
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Standard 1/3-Stop Increments
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— | f/1.4, f/1.6, f/1.8, f/2.0, f/2.2, f/2.5, f/2.8, f/3.2, f/3.5, f/4.0, f/4.5, f/5.0, f/5.6, f/6.3, f/7.1, f/8.0, f/9.0, f/10, f/11, f/13, f/14, f/16 |
|
Light Transmission Rule
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— | Each full f-stop increase cuts light passing through the lens by exactly 50% (1 stop / 1 EV) |
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Diffraction Limit Physics
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— | Airy disk diameter = 2.44 × λ × N. At f/16 and f/22 on high-res digital sensors, diffraction visibly softens fine detail |