Calculate Exposure Value from aperture, shutter speed, and ISO
Exposure Value (EV) is a standardized number that combines aperture, shutter speed, and ISO into a single figure representing the total amount of light reaching your camera sensor. Understanding EV is one of the most important concepts in photography — it gives you a universal language to describe lighting conditions and camera settings regardless of the specific combination of controls you use. The concept of EV was originally developed by German camera manufacturer Leitz in the 1950s as a way to simplify exposure controls. Rather than adjusting aperture and shutter speed independently, photographers could dial in a single EV number. Today, EV remains the gold standard for describing both exposure settings and ambient light levels, used everywhere from camera metering systems to professional lighting measurement. Our EV Calculator takes the guesswork out of exposure by computing the Exposure Value from your three main camera settings. Enter your f-stop, shutter speed, and ISO, and instantly see the resulting EV, the equivalent EV at ISO 100 (used for comparing scenes), the estimated lux value (illuminance), and the matching real-world lighting condition. If you use an ND (neutral density) filter, the calculator shows you the adjusted shutter speed needed to maintain correct exposure. Why does EV matter in practice? If you understand that a sunny day typically falls at EV 15-16 and indoor office lighting sits around EV 10, you can confidently choose starting settings before you even look through the viewfinder. The Sunny 16 rule — f/16, 1/ISO seconds at ISO 100 — works because bright sunlight is reliably EV 16. Knowing EV lets you predict how many stops you need to open up when moving from bright outdoor to indoor environments. Equivalent exposures are another powerful application of EV. Any combination of aperture, shutter speed, and ISO that produces the same EV gives you identical brightness. This is the foundation of the exposure triangle — you can trade depth of field for motion blur (or vice versa) without changing overall image brightness, as long as you keep EV constant. Our calculator automatically finds five equivalent exposure combinations for you, making it easy to choose the settings that match your creative intent. ND filters reduce the amount of light entering the lens by a fixed number of stops. An ND8 filter blocks 3 stops, meaning you need to multiply your original shutter speed by 2³ = 8 to maintain the same exposure. Our calculator handles this math automatically — just select your ND filter and see the adjusted shutter speed instantly. This is especially useful for long-exposure photography in bright daylight or for achieving shallow depth of field in bright conditions. Photographers of all skill levels benefit from understanding EV. Beginners can use scene presets to get a feel for how different conditions map to camera settings. Intermediate photographers can use the equivalent exposures table to understand the exposure triangle in concrete terms. Advanced photographers use EV to rapidly adapt to changing light without losing their creative vision. Use this calculator alongside your camera's histogram for the best results. While EV gives you a great starting point, the histogram tells you whether highlights are clipping or shadows are too deep for a specific scene. Together, EV theory and histogram feedback give you complete control over exposure.
Understanding Exposure Value
What Is Exposure Value (EV)?
Exposure Value (EV) is a single number that represents the combination of aperture (f-stop) and shutter speed that gives correct exposure for a given scene brightness, at a specific ISO. At ISO 100, EV 0 corresponds to f/1.0 at 1 second. Each whole stop increase in EV halves the light — either by closing the aperture one stop, doubling the shutter speed, or halving the ISO. EV values for common photographic scenarios range from about −6 for starry skies to +18 for sunlit beaches and snow. The EV at ISO 100 (EV100) is especially useful for comparing scene brightness across different ISO settings, as it removes the ISO variable entirely.
How Is EV Calculated?
The fundamental formula is: EV = log₂(N² / t), where N is the f-number (aperture) and t is the shutter speed in seconds. At ISO 100 this is the direct EV100. For other ISOs: EV_ISO = log₂(100 × N² / (ISO × t)). Illuminance (lux) is related by: Lux = 2.5 × 2^EV100. ND filters extend the shutter speed by: t_new = t_original × 2^(ND_stops). Exposure compensation simply adds or subtracts from the calculated EV: EV_compensated = EV + EC. These formulas are why the Sunny 16 rule works: at f/16, ISO 100, shutter 1/100s (≈1/125s) gives EV ≈ 16, matching bright sunlight.
Why Does EV Matter?
EV gives photographers a universal language to describe light and exposure settings. Instead of memorizing specific aperture-shutter combinations for every situation, you can learn that portraits in open shade need roughly EV 12, wedding receptions EV 8-10, and golden hour outdoor EV 13-14. This knowledge transfers across all ISO settings and camera systems. EV is also the basis for camera metering — your meter measures scene brightness in EV units and sets exposure accordingly. Understanding EV helps you override metering correctly (such as adding +1 to +2 EV for snow scenes that meters underexpose) and predict exposure before you shoot.
한계 및 주의사항
EV is a mathematical abstraction based on average scene reflectance (18% gray). Real scenes deviate from this average — a scene with a bright window and dark interior may have a lighting range of 10-12 EV stops, far exceeding what any camera sensor can capture simultaneously. EV also does not account for lens transmission losses, filter vignetting, or sensor quantum efficiency differences between cameras. The lux estimate is an approximation based on the Sunny 16 rule; actual illuminance varies with sky conditions, latitude, and season. Equivalent exposures may not give identical results in all situations due to reciprocity failure in long film exposures.
공식
Where N is the f-number (aperture) and t is shutter speed in seconds. EV₁₀₀ represents scene brightness independent of ISO, making it ideal for comparing lighting conditions.
The full EV formula including ISO sensitivity. Increasing ISO by one stop (doubling) raises EV by 1, reflecting a brighter exposure from the same scene.
Approximates the illuminance falling on the scene in lux (lumens per square meter), derived from the Sunny 16 rule assuming 18% average reflectance. Useful for correlating camera settings with light meter readings.
Calculates the new shutter speed needed to maintain the same exposure when an ND filter is attached. An ND8 filter (3 stops) multiplies the shutter speed by 8.
Reference Tables
EV to Lighting Condition Reference
| EV₁₀₀ | Lighting Condition | Approx. Lux | Example |
|---|---|---|---|
| -6 | Starry night sky | 0.002 | Rural area, no moon, Milky Way visible |
| -4 | Crescent moon | 0.01 | Very dark night, faint moonlight |
| -2 | Full moon overhead | 0.04 | Bright moonlit night |
| 0 | Deep twilight | 0.16 | 15-30 minutes after sunset |
| 2 | Dim ambient | 0.6 | Candlelit dinner, holiday lights |
| 5 | Dimly lit interior | 5 | Restaurant, museum gallery |
| 8 | Bright indoor | 40 | Well-lit office, studio with windows |
| 10 | Overcast daylight | 160 | Cloudy day, open shade |
| 12 | Bright cloudy | 640 | Overcast outdoor, even lighting |
| 14 | Hazy sun | 2,500 | Slightly cloudy sky, soft shadows |
| 15 | Sunny day | 5,000 | Sunny 16 rule — bright direct sunlight |
| 16 | Bright beach/snow | 10,000 | Highly reflective surfaces in sun |
Common ND Filter Conversion
| Filter | Optical Density | Stops Reduced | Light Transmission | Multiply Shutter By |
|---|---|---|---|---|
| ND2 | 0.3 | 1 | 50% | 2× |
| ND4 | 0.6 | 2 | 25% | 4× |
| ND8 | 0.9 | 3 | 12.5% | 8× |
| ND16 | 1.2 | 4 | 6.25% | 16× |
| ND64 | 1.8 | 6 | 1.56% | 64× |
| ND1000 | 3.0 | 10 | 0.1% | 1024× |
Worked Examples
Calculate EV for a Sunny Day Portrait
EV = log₂(100 × N² / (ISO × t)) = log₂(100 × 5.6² / (200 × 1/500))
= log₂(100 × 31.36 / 0.4) = log₂(7,840)
= 12.94 ≈ EV 13
EV₁₀₀ = log₂(N² / t) = log₂(5.6² / (1/500)) = log₂(31.36 × 500) = log₂(15,680) = 13.94 ≈ 14
Lux ≈ 2.5 × 2^14 = 2.5 × 16,384 ≈ 40,960 lux
Finding Equivalent Exposures
Opening from f/8 to f/2.8 is 3 stops brighter (8 → 5.6 → 4 → 2.8)
To compensate, increase shutter speed by 3 stops: 1/250 → 1/500 → 1/1000 → 1/2000
Verify: EV = log₂(100 × 2.8² / (400 × 1/2000)) = log₂(100 × 7.84 / 0.2) = log₂(3,920) ≈ 11.94
Original: log₂(100 × 64 / 0.4) = log₂(3,920) ≈ 11.94 — confirmed equal
Calculating Shutter Speed with an ND Filter
ND1000 blocks 10 stops of light
t_adjusted = t_original × 2^10 = (1/125) × 1024
= 1024/125 = 8.19 seconds
Round to the nearest standard shutter speed: 8 seconds
How to Use the EV Calculator
Choose a Scene Preset or Enter Settings
Click one of the scene preset buttons (Sunny Day, Cloudy Day, Indoor, Night, Sports) to auto-fill typical camera settings for that scenario. Or manually select your aperture (f-stop), shutter speed, and ISO from the dropdown menus to match your exact camera configuration.
Apply Exposure Compensation and ND Filter
Drag the Exposure Compensation slider to add or subtract stops from the calculated EV — this simulates your camera's +/- compensation dial. If you are using a neutral density filter, select it from the ND Filter dropdown to see the adjusted shutter speed you need to maintain correct exposure with the filter attached.
Read the EV and Lighting Condition
The large number at the top shows your Exposure Value. The EV scale bar below it shows where your EV falls across the night-to-outdoor spectrum. The Lighting Condition label tells you what real-world lighting scenario matches your settings, from starry night sky to bright beach and snow.
Use Equivalent Exposures for Creative Control
The Equivalent Exposures table lists other aperture/shutter/ISO combinations that produce the same brightness. Use these to swap depth of field for motion blur — for example, switch from f/8 at 1/125s to f/2.8 at 1/1000s for the same EV but a much shallower depth of field and frozen motion.
자주 묻는 질문
What is Exposure Value (EV) in photography?
Exposure Value (EV) is a number that describes the combination of aperture, shutter speed, and ISO that produces a given exposure. At ISO 100, EV 0 corresponds to f/1.0 at 1 second. Each whole-stop increase in EV halves the total light — you can achieve this by closing the aperture one stop, doubling the shutter speed, or halving the ISO. EV values for real-world photography range from about -6 for starry skies to +18 for brightly lit beaches. The concept was developed in the 1950s to give photographers a universal single-number way to describe exposure, independent of which specific combination of settings they use.
What is the difference between EV and EV at ISO 100?
EV (Exposure Value) is calculated including ISO: EV = log₂(100 × N² / (ISO × t)). This gives you the actual metered exposure value for your specific ISO. EV at ISO 100 (EV100) removes the ISO factor: EV100 = log₂(N² / t). EV100 is the standardized scene brightness independent of ISO sensitivity, making it ideal for comparing lighting conditions across different cameras and ISOs. Light meters often measure in EV100 units. When you increase ISO, your camera's EV readout goes up (brighter exposure) but the scene's actual EV100 stays constant — you're just amplifying the signal, not adding more light.
How does an ND filter affect exposure value?
A neutral density (ND) filter blocks light without affecting color, effectively reducing the scene's brightness as seen by the sensor. An ND2 blocks 1 stop (cuts light in half), ND4 blocks 2 stops, ND8 blocks 3 stops, ND16 blocks 4 stops, ND64 blocks 6 stops, and ND1000 blocks approximately 10 stops. To maintain the same exposure (same EV), you multiply your shutter speed by 2^(ND stops) — so an ND8 requires 8x longer shutter speed. Photographers use ND filters for long-exposure daytime photography (silky waterfalls, light trails), achieving wide apertures in bright light for shallow depth of field, or extending video exposure to match the 180-degree shutter rule.
What are equivalent exposures and why do they matter?
Equivalent exposures are different combinations of aperture, shutter speed, and ISO that all produce the same Exposure Value — meaning the same overall image brightness. For example, f/5.6 at 1/250s ISO 400 is equivalent to f/8 at 1/125s ISO 400, or f/4 at 1/500s ISO 400. The practical significance is that you can trade one control for another to achieve a creative effect without changing brightness. Open the aperture for shallower depth of field and compensate with a faster shutter. Use a longer shutter speed to show motion blur and compensate by closing the aperture or lowering ISO. Understanding equivalent exposures is the core of mastering manual exposure.
What does the lux value in this calculator represent?
Lux is the SI unit of illuminance — the amount of light falling on a surface per unit area. One lux equals one lumen per square meter. The lux estimate in this calculator uses the formula: Lux = 2.5 × 2^EV100, derived from the relationship between photographic exposure and photometric luminance assuming an average 18% gray scene reflectance. Typical values: starlit night 0.001 lux, full moon 1 lux, indoor office 300-500 lux, overcast day 1,000-10,000 lux, bright sunlight 50,000-100,000 lux. This is an approximation — actual scene illuminance varies with sky conditions, latitude, and surface reflectance.
What is the Sunny 16 rule and how does it relate to EV?
The Sunny 16 rule states that in bright direct sunlight, correct exposure is achieved with f/16 aperture and a shutter speed equal to 1/ISO. At ISO 100, that's f/16 and 1/100s (use 1/125s in practice). Plugging this into the EV formula: EV = log₂(100 × 16² / (100 × 1/100)) = log₂(16²) = log₂(256) ≈ 8 + 8 = 16. So bright sunlight is reliably EV 16 — and the Sunny 16 rule is just a memorable shorthand for this fact. Knowing that EV 16 = bright sun, EV 12 = overcast, and EV 8-10 = indoor, you can quickly estimate starting exposure settings for any scene using only mental math.