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Exposure Value (EV) Calculator

Aperture (f/stop)

Shutter (s)

ISO

EV100

11.9

vs Sunny 16

-3.1 EV

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We're working on a comprehensive educational guide for the Exposure Value (EV) Calculator in your language. The content below is shown in English.

Qu'est-ce que Exposure Value (EV) Calculator?

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The Exposure Value (EV) Calculator quantifies the total amount of light in a photographic exposure using a single numerical scale that combines aperture, shutter speed, and ISO sensitivity into one comparable number. EV was originally defined at ISO 100 (EV100) and is formally standardized by the American National Standards Institute in ANSI PH2.7-1973. An EV of 0 corresponds to one second exposure at f/1.0 (at ISO 100), and each increment of 1 EV represents a doubling of the light (equivalent to 1 stop). The EV scale allows photographers to express scene brightness independently of the specific camera settings used. A sunny day at noon in mid-latitudes is approximately EV 15, while a candlelit room is around EV 2–4. When you know the EV for a scene, you can choose any combination of aperture, shutter speed, and ISO that produces the same total exposure. This is the exposure triangle — the fundamental concept that underlies all photographic exposure decisions. EV calculations are also used in flash photography, where guide numbers quantify flash output in EV units, and in metering systems, where incident light meters and reflected light meters output EV readings that camera exposure systems interpret. Photographers use EV values to compare scene brightness across lighting conditions, to understand automatic exposure shifts made by the camera, to set exposure compensation in fraction-stop increments, and to communicate lighting requirements to assistants and cinematographers. The EV system elegantly unifies the exposure triangle into a single number, enabling precise, systematic exposure control.

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Formule

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f(x)

EV = log2(N² / t) at ISO 100, where N = f-number, t = shutter speed in seconds
EV (at any ISO) = EV100 - log2(ISO / 100)
For EV at ISO S: EV_S = log2(N² × S / (t × 100))
Alternatively: EV = log2(f² / t) + log2(ISO/100)
Scene EV (reflected): EV = log2(L × S / K), L = luminance (cd/m²), K = reflected light meter constant (~12.5)

Légende des variables

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Symbole	Nom	Unité	Description
EV	Exposure Value	EV	A unitless number representing the total light reaching the sensor. Higher EV = brighter scene or more exposure.
N	Aperture (f-number)	f-stop	The f-number of the lens aperture (e.g., f/2.8 means N=2.8).
t	Shutter Speed	seconds	The duration of the exposure in seconds (e.g., 1/250 s = 0.004 s).
S	ISO Sensitivity	ISO	The ISO/ASA speed of the sensor or film. Reference value is ISO 100.
L	Scene Luminance	cd/m²	Reflected luminance of the scene in candelas per square meter, measured by a luminance meter.

Comment Exposure Value (EV) Calculator

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1Step 1: Note your camera settings: aperture (f-number), shutter speed (seconds), and ISO.
2Step 2: Calculate EV100 = log2(f² / t). For f/8 and 1/125 s: f² = 64, t = 0.008 s. EV100 = log2(64/0.008) = log2(8000) = 12.97 ≈ 13.
3Step 3: If ISO differs from 100, adjust: EV_actual = EV100 + log2(ISO/100). At ISO 400: +2 stops adjustment.
4Step 4: Compare to scene brightness tables (e.g., EV 15 = bright sun, EV 12 = overcast, EV 6 = indoor fluorescent).
5Step 5: Use the EV to find equivalent exposures: any combination of N and t satisfying log2(N²/t) = target EV produces the same exposure.
6Step 6: Apply exposure compensation (+/- EV) for high-key or low-key subjects where the meter would otherwise give incorrect readings.

Exemples résolus

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Exemple 1Sunny outdoor portrait

Donné:f/8, 1/250 s, 100

Résultat:EV 14

f² = 64, t = 0.004 s. EV = log2(64/0.004) = log2(16000) = 13.97 ≈ EV 14. This matches the 'sunny 16' rule — a sunny day is EV 14–16.

Exemple 2Indoor available light

Donné:f/1.8, 1/60 s, 1600

Résultat:EV 8 (adjusted for ISO 1600)

EV100 = log2(1.8²/0.0167) = log2(3.24/0.0167) = log2(194) = 7.6. ISO boost: log2(1600/100) = 4 stops. EV_scene ≈ 7.6 (indoor tungsten).

Exemple 3Long exposure night sky

Donné:f/2.8, 30 s, 3200

Résultat:EV 0 — Milky Way shooting conditions

EV100 = log2(7.84/30) = log2(0.26) = -1.9. ISO adjustment: +5 stops. Effective EV ≈ 0. Night sky without moon is EV -1 to 1.

Exemple 4Studio strobe (guide number method)

Donné:58, 3, 100

Résultat:f/19.3 at 1/200 s (sync speed) — EV 16

f-number = GN / distance = 58 / 3 = f/19.3. At 1/200 s (flash sync): EV = log2(19.3²/0.005) = log2(74,650) = 16.2.

Applications pratiques

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Photographers setting manual exposure on film cameras without in-body metering.

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Cinematographers calculating exposure for mixed lighting scenes across multiple setups.

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Light meter calibration and verification against known EV reference standards.

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Understanding and setting exposure compensation for challenging metering situations.

Cas particuliers

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EV at non-standard ISOs

EV100 is the reference, but any ISO can be used. To find the scene EV: EV_scene = EV100 + log2(ISO/100). At ISO 800, your camera's EV100 equivalent is 3 stops higher — a reading of EV 5 at ISO 800 represents an EV 8 scene.

Video exposure and EV

In video, EV is fixed by the 180° shutter rule (shutter = 2× frame rate) and aperture choice; ISO is adjusted to match the resulting EV to the scene brightness. Video cameras often display exposure using IRE levels or waveform monitors rather than EV, but the underlying EV math is identical.

When input values approach zero or become negative, the Exposure Ev Calculator

When input values approach zero or become negative, the Exposure Ev Calculator calculation may produce undefined or misleading results. Always validate that inputs fall within the model's valid range before interpreting outputs. Extreme values should be flagged for manual review.

EV Reference Values for Common Lighting Conditions (ISO 100)

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Lighting Condition	EV (ISO 100)	Example Exposure
Direct sun, white sand/snow	16–17	f/16, 1/125 s
Bright sun, clear sky	15	f/16, 1/100 s
Slightly overcast	13–14	f/8, 1/250 s
Open shade / heavy overcast	11–12	f/5.6, 1/250 s
Sunset (sun near horizon)	9–10	f/4, 1/125 s
Office fluorescent / window light	7–8	f/2.8, 1/60 s
Home interior (tungsten lamps)	5–6	f/1.8, 1/30 s
Candlelight	3–4	f/1.4, 1/4 s
Night street with lights	2–3	f/1.8, 1 s
Milky Way / starry sky	-1 to 1	f/2.8, 20–30 s

Questions fréquentes

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What does EV 0 mean in practical terms?

EV 0 at ISO 100 is achieved with an exposure of 1 second at f/1.0. This is an extremely dim light level — approximately the brightness of a single candle at 1 meter. Most modern cameras can meter and expose correctly down to EV -2 or below using electronic front curtain shutters and high-ISO capabilities.

How is EV related to the exposure triangle?

EV mathematically combines all three exposure triangle elements. Every full stop of aperture change (e.g., f/2.8 to f/4), shutter speed change (1/125 to 1/250), or ISO change (ISO 200 to ISO 100) shifts EV by exactly 1.0. Understanding EV makes it easy to see why equivalent exposures work: you can trade one variable for another as long as the total EV stays constant.

What is the Sunny 16 rule and how does it relate to EV?

The Sunny 16 rule states that in direct sunlight, correct exposure at ISO 100 is f/16 at 1/100 s (approximately 1/ISO seconds). EV for f/16 at 1/100 s = log2(256/0.01) = log2(25,600) = 14.6 ≈ EV 15. This is why direct sunlight is defined as EV 15 at ISO 100 — the Sunny 16 rule and EV scale are perfectly consistent.

Can I use EV to set exposure on a camera without a built-in meter?

Yes. Measure scene EV with an incident light meter (measures EV directly) or calculate it from a reference (Sunny 16, published tables). Then use an EV lookup table to find any combination of aperture and shutter speed at your working ISO that matches the target EV. This is exactly how photographers used Ansel Adams' Zone System with manual cameras.

What is exposure compensation and how does it relate to EV?

Exposure compensation (EC) adds or subtracts EV from the camera's metered exposure. +1 EV doubles the exposure (opens aperture 1 stop, slows shutter 1 stop, or doubles ISO). Negative EC reduces exposure. Use +EC for snow, white walls, and bright backgrounds; use -EC for dark subjects on dark backgrounds where the meter overexposes to achieve 'middle gray.'

How do luminance meters display EV?

Incident and spot luminance meters (Sekonic, Gossen) measure scene luminance in EV units, typically at a reference ISO. The meter displays an EV reading that corresponds to a specific combination of aperture and shutter speed shown on its calculator dial. Digital meters show recommended aperture/shutter combinations directly. The relationship is: EV = log2(L × S / K), where L is luminance, S is ISO, and K is the reflected meter calibration constant (12.5 for Sekonic meters).

How does HDR photography relate to EV?

HDR (High Dynamic Range) photography merges multiple exposures at different EV settings (typically ±2 EV, ±1 EV brackets) to capture scenes whose dynamic range exceeds the sensor's single-shot capability. A typical scene may have a dynamic range of 12–16 EV from deepest shadow to brightest highlight. A camera sensor captures 12–15 EV of dynamic range, and post-processing software tone-maps the merged HDR to fit this into the display range.

Erreurs courantes à éviter

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!Confusing EV with exposure compensation — EV is an absolute measure of brightness; EC is a relative adjustment from metered EV.
!Forgetting that EV tables are referenced to ISO 100 — adjustments are needed for other ISOs.
!Believing EV uniquely determines aperture/shutter settings — any combination on the EV curve produces the same exposure, giving the photographer creative choice of DOF and motion blur.
!Using reflected EV readings for subjects that are not 18% gray without applying appropriate exposure compensation.

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Conseil Pro

Carry an EV reference card or use a metering app on your phone when shooting manual on film or digital cameras without reliable metering. Sekonic's Light Meter University online provides downloadable EV reference tables covering sunrise to midnight.

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Le saviez-vous?

The APEX (Additive system of Photographic EXposure) system, introduced in 1960, extended EV mathematics to include film speed and luminance as additive logarithmic values on the same scale — enabling simple arithmetic exposure calculations, a predecessor to the digital camera's automatic exposure algorithms.

Regional Guides

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🇺🇸 US▾

Uses US customary units and standards where applicable

🇬🇧 UK▾

May require conversion to metric units or British standards

🇪🇺 EU▾

Follows EU conventions and SI units where applicable

Références

📖Difficulté:Intermédiaire

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