Exposure Calculator

How to use the photography exposure value calculator

What this calculator does. This tool converts the three core camera settings – aperture, exposure time, and ISO – into an ISO-adjusted exposure value (EV). It can also work backward: give it a target EV and two known camera settings, and it can solve the third. EV is a compact way to compare combinations of settings that correspond to broadly similar lighting conditions. It is useful for planning manual exposures, checking equivalent settings, and understanding how one-stop changes interact. It does not meter the light in front of your camera, predict subject reflectance, guarantee highlight protection, or replace your camera histogram and meter.

When to use it. Use the calculator when you are learning manual exposure and want to see how aperture, shutter speed, and ISO combine; when you are moving between daylight, shade, interiors, and night scenes; when a creative choice fixes two settings and you need a third; or when you want a numerical EV reference before a film or digital shoot. Nikon's guide to aperture, shutter speed, and ISO explains why these three controls must be balanced together.

How to calculate. The calculator opens with a complete demonstration: f/8, 1/500 s, and ISO 200. Its EV and Excel workbook are available immediately. To use your own values:

1. Choose an Aperture f-stop, a Shutter speed, and Film or camera sensor's sensitivity preset. Their numeric companion fields update automatically.
2. For a nonstandard value, choose Custom / solve from EV in the relevant preset and type the numeric value in its companion field. Use decimal points, not decimal commas or scientific notation.
3. To solve one missing setting, choose Custom for that setting, leave its numeric field empty, and enter a target Exposure value (EV). You can also edit EV while exactly one Custom preset is active; that Custom setting becomes the solved variable.
4. Read the live EV, solved camera settings, and the highlighted lighting-guide row. Then use Download Excel to save the current typed model as an OOXML workbook.
5. Reset clears the demonstration and all data fields. After Reset, Download Excel is disabled until a complete valid exposure state is entered again.

Input guide. Aperture f-stop is the preset selector for lens f-number; Focal ratio is its numeric value and is required unless aperture is the one setting being solved. It accepts a positive decimal from 0.1 to 256, such as 8 for f/8. A smaller f-number represents a wider aperture; typing commas, symbols, or zero is rejected. Shutter speed is the preset selector for exposure duration; Duration of exposure is the required time in seconds unless shutter time is being solved. It accepts 0.000001 through 86,400 seconds, such as 0.002 for 1/500 s. A larger duration lowers EV when aperture and ISO are unchanged. Film or camera sensor's sensitivity selects a standard ISO; ISO value is the required numeric sensitivity unless ISO is being solved. It accepts 1 through 3,000,000, such as 200. Higher ISO lowers the ISO-adjusted EV for the same aperture and time. Exposure value (EV) is normally calculated, but it becomes a target when one Custom setting is active; target EV accepts signed decimals from -30 to +30. A common mistake is to treat EV as a direct brightness guarantee: it describes the setting relationship, while the scene and metering still matter.

Output guide. Exposure value (EV) is the primary result, shown to two decimals. Larger positive values correspond to brighter-light exposure combinations; low or negative values correspond to much darker conditions. Aperture, Shutter time, and ISO repeat the canonical settings used by the model, so a backward-solved value is visible immediately. Closest guide maps the calculated EV to a broad lighting band in the table. It is an interpretation aid, not a recommendation or a substitute for metering. The Exposure value lighting guide table uses the EV column for the numeric band and Approximate lighting situation for representative scenes; the active row follows the current EV.

Worked example. With f/8, 1/500 second, and ISO 200, the model evaluates EV = log₂(100 × 8² ÷ (200 × 0.002)). The ratio inside the logarithm is 16,000, and log₂(16,000) is 13.965784..., displayed as EV +13.97. That falls in the EV 13 – 14 guide band, which is associated with cloudy-bright to weak hazy sun conditions. If you instead keep f/8 and ISO 200 but lengthen the exposure time, EV decreases because more time is being allowed for the exposure.

Learn more. For a practical explanation of what exposure means at the sensor and how shutter time changes it, see Adobe's photography exposure guide. For the tradeoff between sensitivity and image quality, Nikon's ISO sensitivity guide gives useful context.