Manual photographer comparing apertures
Translate an aperture change into an equal-setting shutter time.
Enter actual f-number, seconds, ISO and comparison f-number.
Gets signed stop difference and comparison time without scene presets.
Exposure Setting Calculator
Calculate EV100 and ISO-normalized setting indexes plus an equal-exposure shutter time from aperture, seconds, ISO, and comparison aperture.
Built for Photography1 documented formula1 guided projectPrivate in your browser
Use this result well
A quick decision brief for this specific tool
Inputs that matter
Entered f-number, shutter time in seconds, ISO setting and one comparison f-number
Output to expect
EV100 setting index, ISO-normalized setting index, relative factor and equal-exposure comparison shutter time
How it works
Calculate log₂(N²/t), apply the entered ISO normalization and preserve N²/t when solving the comparison time
- Use a calibrated meter/histogram and the real scene to decide exposure; the setting index does not measure scene luminance or guarantee a creative/correct result.
- Verify flash/filter effects, lens transmission, shutter/aperture accuracy, reciprocity, dynamic range, sensor response and camera limits separately.
Choose your path
Built around the job you need to finish
Record exposure-setting relationships and an equal-exposure aperture/time comparison without predicting that a real scene will be correctly exposed.
Long-exposure photographer
Use direct seconds instead of a shutter-denominator-only interface.
Enter a multi-second time and inspect the same formulas as short exposures.
Avoids reciprocal-input ambiguity while retaining reciprocity and filter checks.
Film or digital technician auditing a record
Separate EV100 setting math from scene metering and device response.
Review EV100, ISO normalization and relative factor, then verify the real meter/camera/film.
Does not interpret a setting index as scene luminance or correctness.
Authoritative checks for this tool
Outputs and checklists are planning aids. Review the linked current authorities and the records, terms, instructions, and requirements that apply to your exact situation before a consequential decision.
- A Basic Look at the Basics of ExposureNikon USA · First-party explanation of how aperture, shutter time and ISO settings relate while the actual scene and creative outcome still require metering and judgment.
- Photography Glossary — Exposure ValueNikon USA · Manufacturer definition of EV as a number representing aperture/shutter combinations with the same exposure effect when scene brightness is unchanged.
- Understanding ISO SensitivityNikon USA · First-party ISO-setting context and stop relationship; camera response, noise and processing remain camera-specific.
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Projects using Exposure Setting Calculator
This tool is part of these guided projects. Each project provides step-by-step instructions with checklists and all the tools you need in one place.
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Reference & details
How it works
Updated August 2026
How it works
Updated August 2026EV100 Setting Index
The aperture/time combination is summarized at the ISO 100 reference. A one-unit increase in this index represents half the admitted exposure for the same scene, not double image brightness.
EV100 = log₂(N² / t)Equal Aperture-Time Relationship
At unchanged ISO, the comparison shutter time preserves N²/t. A larger comparison f-number requires a proportionally longer time; the signed aperture difference is shown in stops.
t₂ = t₁ × (N₂/N₁)²ISO Normalization and Boundary
The entered ISO shifts the setting index mathematically. Actual scene luminance, meter calibration, sensor or film response, flash, filters, reciprocity, dynamic range, and creative intent are not measured.
indexISO = EV100 − log₂(ISO/100)Updated: August 2026
Example Scenarios
Enter 0.008 seconds rather than a denominator, keep ISO unchanged, and calculate the time that preserves the same aperture/time ratio at f/8. Then confirm the real scene with a meter or histogram.
Enter two seconds as 2, not 1/2 or a denominator. The same EV100 math applies, but film reciprocity, sensor heating, filters, subject motion, and shutter accuracy remain outside the result.
Record aperture, actual seconds, ISO, EV100, and the normalized index for reproducibility. Keep metering mode, scene luminance, flash, filters, camera/film response, and processing with the separate capture record.
Common Mistakes to Avoid
Common Mistakes to Avoid
Reading +1 EV100 as twice the recorded brightness
For the same scene and ISO reference, +1 in the aperture/time index corresponds to half the admitted exposure quantity. Image brightness is not predicted by this tool.
Treating equal mathematical settings as physically identical captures
Verify lens transmission, aperture and shutter accuracy, filters, flash behavior, reciprocity, motion, sensor/film response, and processing in the actual system.
FAQ
No. It summarizes aperture and time against an ISO 100 reference. Correctness depends on scene luminance, metering, reflectance, dynamic range, desired rendering, and the actual capture system.
Seconds represent both short and long exposures without ambiguity. For example, 0.008 is 1/125 second and 2 is a two-second exposure.
It preserves the same N²/t ratio at the same entered ISO. It does not compensate for lens transmission, flash duration, filter factors, reciprocity failure, or device calibration.
EV100 is logarithmic in N²/t. Increasing N²/t by two raises EV100 by one while halving the aperture-time exposure quantity for the same scene.
The setting record can be a starting point, but film reciprocity, development, flash output/duration/sync, filters, and meter calibration require separate data and adjustments.
About Exposure Setting Calculator
This tool compares camera-setting relationships. It accepts shutter time directly in seconds, handles short and multi-second exposures, and solves one comparison aperture/time pair. It does not meter a scene or declare an exposure correct.