Exposure Value (EV)
Enter aperture f-number, shutter speed in seconds and ISO to get EV = log2(N²/t) − log2(ISO/100), a single number for the light in the scene.
EV
—
Exposure Value (EV): a single number for light
The Exposure Value rolls aperture and shutter speed into one scale: EV = log₂(N²/t), where N is the f-number and t is the shutter time in seconds. Going up +1 EV halves the light hitting the sensor; dropping −1 EV doubles it. A few reference points at ISO 100: EV 15 is Sunny 16 (bright daylight), EV 12 overcast, EV 8 a bright interior, EV 3 a candle-lit room, EV −1 a close-up of one candle, and EV −6 a landscape under stars. When the histogram sits balanced, with nothing clipped at either end, it usually lines up with the metered EV. Reach for exposure compensation (±EV) on bright scenes (snow +1) or dark ones (black cat −1). Lightroom's "Exposure" slider runs in EV stops, and HDR brackets usually grab 3–5 frames at ±1 or ±2 EV intervals.
Applications
You'll use it to measure available light, keep exposure consistent as scenes shift, put scenes side by side on a common scale, build HDR sequences through bracketing, and dial in Lightroom/Capture One sliders in known stops. It's hard to do without on manual cameras or fixed-exposure setups.
FAQ
Does EV depend on ISO? The bare formula doesn't. But once you map EV to the actual exposure on the sensor, ISO comes in too, since doubling it amounts to +1 EV of sensitivity.
What is "EV 0"? It's 1 second at f/1.0, the original reference point set back in the 1950s.
Why bracket ±2 EV instead of ±1 EV? A high-contrast scene like a sunrise, or an interior shot toward windows, can span 10+ stops. Wider brackets pull in the shadows and the highlights so you have both to merge.
Related Tools
Margin of Safety (Investing)
Computes the margin of safety of an investment: how far the market price sits below the estimated intrinsic value, as a percentage. It's the core concept of Benjamin Graham's value investing — buying an asset for well less than it's worth to build in protection against estimation errors and surprises. The larger the margin, the more comfortable the purchase. A negative margin means the price already exceeds the estimated value. Enter the intrinsic value and the market price.
RVPI (Residual Value to Paid-In)
Computes the RVPI of a private equity fund: the residual value in the portfolio (NAV) divided by the paid-in capital. It's the unrealized multiple, how much is still alive in the holdings the fund hasn't sold, waiting to turn into cash. In a fund's early years, RVPI dominates; as it divests, RVPI falls and DPI rises. The sum of the two is the TVPI. Enter the NAV and the paid-in capital.
TVPI (Total Value to Paid-In)
Computes the TVPI of a private equity or venture capital fund: the total value created, adding what has already been distributed to investors to the residual value still in the portfolio (NAV), divided by the paid-in capital. It's a fund's most complete multiple, summing realized and unrealized — a TVPI of 1.5x means each dollar invested became one and a half in total value. It decomposes into DPI plus RVPI. Enter the distributions, the NAV and the paid-in capital.
HP-12C EVA Project
Computes EVA Economic Value Added of project by HP-12C residual profit over capital with WACC.
Attic R-Value by IECC Climate Zone
Choose a zone from 1 (tropical) to 7 (cold) and get the minimum ceiling insulation the US energy code recommends, ranging from R-30 up to R-60.
LTV (Loan-to-Value) Calculator
Divides the loan amount by the property value to give the LTV percentage, then reads it as conservative, standard, high risk or above usual lending policy.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.