Exposure Calculator
Convert a scene brightness into equivalent aperture, shutter and ISO combinations.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
This exposure model uses EV, aperture and ISO to estimate shutter time. Equivalent settings can give a similar exposure, but they do not make the image identical: aperture changes depth of field, shutter time changes motion blur, and ISO affects noise and highlight headroom.
Worked example
calculated with the default values below
Exposure value (scene brightness) 12 EV · ISO ISO 100 · Preferred aperture 8 f/ Shutter speed 0.01563 s · Shutter speed as a fraction 1/64 · Exposure value at ISO 100 12.00 · Scene brightness Bright overcast to hazy sun · Neutral density to reach 1/2 s 0.0 stops · Shutter at ISO 100 1/64
General background references
Disclaimer
These calculators give general estimates. Sizing, pricing, availability and standards vary by brand, retailer and country, so treat the output as a starting point and confirm it against the seller's or authority's own figures.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
t = N² × 2^(-EV) × 100 ÷ ISO
- EV
- exposure value (scene brightness)
- N
- aperture f-number
- ISO
- ISO sensitivity
- t
- shutter speed (s)
Equivalent exposure does not preserve depth of field, motion blur or noise. ND stops to lengthen an exposure to 0.5 s are estimated only when t > 0.5 s; brightness labels use approximate EV bands.
Frequently asked questions
Do equivalent exposure settings make the same picture?
They can produce a similar exposure, but not the same image characteristics. A wider aperture changes depth of field, a longer shutter changes motion blur, and higher ISO affects noise and highlight detail. The calculator estimates exposure time and an ND-filter adjustment; it does not model a specific camera or scene.