Exposure Calculator

About the Exposure Calculator

The exposure triangle—aperture, shutter speed, and ISO—is the foundation of photography. Every photograph is determined by how much light reaches the sensor (controlled by aperture and shutter speed) and how sensitive the sensor is to that light (ISO). Changing one setting requires compensating with another to maintain the same overall exposure.

This exposure calculator helps photographers find equivalent exposure settings. Start with a known-good exposure and adjust any parameter to see how the others must change. It computes the Exposure Value (EV), shows equivalent combinations, and includes reference tables for common lighting conditions.

The calculator accounts for the nonlinear relationship between f-stops (each full stop doubles or halves the light) and provides third-stop precision for modern cameras. It also includes an ND filter calculator, reciprocity failure compensation for film shooters, and the classic Sunny 16 rule as a starting point.

Whether you're a beginner learning manual exposure for the first time or an experienced photographer calculating long exposures with ND filters, it gives the mathematical foundation for precise exposure control. The equivalent settings table is especially useful when you need to prioritize one parameter (fast shutter for sports, wide aperture for bokeh) while maintaining correct exposure.

When This Page Helps

Understanding exposure equivalence is essential for creative photography. This calculator quickly shows all equivalent exposure settings so you can prioritize the creative parameter that matters most—depth of field, motion control, or noise—while maintaining correct brightness. This calculator handles the repetitive math so you can compare scenarios, verify assumptions, and focus on the decision the result supports.

How to Use the Inputs

1. Enter your current aperture, shutter speed, and ISO for a reference exposure.
2. Adjust any one parameter and see the compensating changes needed.
3. Use the EV reference table to find starting settings for your lighting condition.
4. Add ND filter stops to calculate long exposure times.
5. Review equivalent exposure combinations in the comparison table.
6. Optionally enable reciprocity failure correction for film shooters.

Example Calculation

Tips & Best Practices

• Start with the Sunny 16 rule as a sanity check for your meter readings.
• For long exposures with ND filters, use the built-in ND calculator to avoid mental math errors.
• Each full f-stop change doubles or halves the light: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22.
• In auto-ISO mode, set a minimum shutter speed of 1/(focal length) to avoid camera shake.
• Bracket exposures by ±1 EV in tricky lighting to ensure one frame is correctly exposed.
• Modern cameras meter accurately, but snow, backlight, and dark scenes fool meters—use EV compensation.

The Exposure Triangle Explained

The exposure triangle describes the interplay between aperture (size of the lens opening), shutter speed (duration of exposure), and ISO (sensor sensitivity). Each parameter is measured in "stops"—a consistent unit where one stop doubles or halves the amount of light.

Aperture is expressed as an f-number: f/2.8 admits 4x more light than f/5.6 (2 stops difference). Shutter speed is linear: 1/60s admits 2x more light than 1/125s (approximately 1 stop). ISO doubles sensitivity per stop: ISO 400 is 2 stops more sensitive than ISO 100.

EV Reference Table

Photographers use EV values to quickly characterize lighting conditions. EV -6 = starlight, EV 0 = deep twilight, EV 5 = indoor home lighting, EV 10 = overcast daylight, EV 13 = light haze, EV 15 = bright direct sunlight, EV 16 = snow or sand in bright sun. These references let you estimate exposure before metering.

ND Filters and Long Exposure

Neutral density filters reduce light entering the lens without affecting color. They're essential for long-exposure effects like smooth water and cloud streaks. Common ND strengths: ND2 (1 stop), ND4 (2 stops), ND8 (3 stops), ND64 (6 stops), ND1000 (10 stops). Stacking multiple ND filters multiplies their effect, but may introduce vignetting or color casts with cheaper filters.

Frequently Asked Questions

• What is Exposure Value (EV)?

  EV is a number representing a combination of aperture and shutter speed. Each 1 EV increment halves the amount of light. EV 0 = f/1.0 at 1 second. EV 15 = bright sunlight.

• How does the Sunny 16 rule work?

  On a sunny day, set aperture to f/16 and shutter speed to 1/ISO (e.g., 1/100 at ISO 100). This gives approximately EV 15.

• What is reciprocity failure?

  Film becomes less sensitive during very long exposures (typically beyond 1 second). The required exposure time must be increased beyond what the meter indicates. Digital sensors don't suffer from this.

• How do ND filters affect exposure?

  Each stop of ND filter requires doubling the exposure time (or widening aperture by 1 stop). A 10-stop ND filter turns a 1/125s exposure into an 8-second exposure.

• What is the base ISO?

  Base ISO is the sensor's native sensitivity with the best dynamic range, typically ISO 100 or 200 on modern cameras. Using base ISO maximizes image quality.

• How do I choose between adjusting aperture, shutter, or ISO?

  It depends on priority: aperture for DOF control, shutter for motion (freeze or blur), ISO as last resort since higher ISO means more noise.