Exposure Calculator
Enter your aperture (f-stop), shutter speed, and ISO to calculate the Exposure Value (EV). You can also reverse-solve: pick any mode to find the aperture, shutter, or ISO that matches a target EV. Add an ND filter to see the compensated shutter speed, enter your focal length to get the minimum hand-hold shutter, and browse a table of equivalent exposures that deliver the same brightness with different settings.
What is Exposure Value (EV)?
Exposure Value, or EV, is a single number that combines aperture, shutter speed, and ISO into one brightness index. The formula is EV = log2(100 x aperture^2 / (ISO x shutter)), where aperture is the f-number, shutter is in seconds, and the ISO is your sensor sensitivity. EV 0 is defined as f/1, 1 second, ISO 100. Each step of 1 EV represents either a doubling or halving of the light reaching the sensor, the same as one full stop. The beauty of EV is that it lets photographers compare lighting conditions at a glance: a sunny day outside is roughly EV 15, a dim restaurant interior might be EV 5. When your camera is in auto mode it is effectively solving for the EV that the light meter measures, then picking aperture and shutter combinations that match. Understanding EV lets you take that control back.
The Exposure Triangle and equivalent exposures
Aperture, shutter speed, and ISO form the "exposure triangle." Any change to one leg must be balanced by compensating changes to the others if you want to keep the same brightness. Open the aperture from f/8 to f/5.6 (one stop more light) and you must either halve the shutter duration, halve the ISO, or do some combination of both. This is called an equivalent exposure, and the Equivalent Exposures section in the steps panel lists several alternatives that produce the same EV as your current settings. Choosing between them is a creative decision: a wider aperture gives shallower depth of field, a faster shutter freezes motion, and a lower ISO keeps noise under control. None of the alternatives is "wrong," each trades one quality for another.
Using ND filters and the reciprocal rule
A neutral density (ND) filter is a piece of darkened glass that reduces the amount of light entering the lens without affecting color. It is measured in stops: a 3-stop ND passes 1/8 of the original light, so you must multiply the shutter duration by 8 to compensate. A 6-stop ND requires 64x the shutter time. The ND compensation field in this calculator takes care of that arithmetic: enter your base settings, add the filter stops, and the compensated shutter appears immediately. ND filters are popular for silky waterfall long exposures in daylight, or for using a wide aperture at low depth of field on a bright day. The reciprocal rule is separate: it estimates the slowest shutter speed at which you can hand-hold the camera without blur from camera shake, taken as 1 divided by your focal length in millimetres (1/50 s for a 50 mm lens). On cropped-sensor cameras multiply the focal length by the crop factor first (a 50 mm lens on an APS-C body behaves like 75 mm).
Scene presets and the Sunny 16 rule
The Sunny 16 rule is the photographer's oldest exposure cheat sheet: in bright direct sunlight, set your aperture to f/16 and your shutter to 1/ISO s (so ISO 100 = 1/100 s, ISO 400 = 1/400 s). That combination gives EV 15, matching direct equatorial sun at solar noon. From there you can adjust for the conditions in the reference table: light overcast subtracts about 1 EV, heavy overcast subtracts 2-3, open shade subtracts 3-4. The table above lists the EV range for the most common shooting situations. These are starting points; actual light varies with latitude, season, time of day, and sky conditions. A light meter or your camera's histogram gives the most accurate reading, but the EV scale lets you sanity-check it instantly.
EV and typical lighting scenes
| EV (ISO 100) | Lighting Scene | Example Settings |
|---|---|---|
| -7 | Deep star fields or aurora | f/2, 30 s, ISO 100 |
| -3 | Quarter moon, open landscape | f/2, 4 s, ISO 100 |
| 0 | Night home interior (dimly lit) | f/2, 0.5 s, ISO 100 |
| 3 | Candle-lit scene | f/2, 1/8 s, ISO 100 |
| 5 | Home interior with typical lamps | f/2.8, 1/15 s, ISO 100 |
| 7 | Sunset or outdoor neon signs | f/4, 1/30 s, ISO 100 |
| 9 | Heavy overcast sky | f/5.6, 1/60 s, ISO 100 |
| 11 | Light overcast, bright shade | f/8, 1/125 s, ISO 100 |
| 13 | Slightly hazy sun | f/8, 1/500 s, ISO 100 |
| 15 | Sunny 16 (bright direct sun) | f/16, 1/100 s, ISO 100 |
| 16 | Bright beach or snow in sun | f/16, 1/200 s, ISO 100 |
| 20 | Extremely bright, near solar | f/32, 1/1000 s, ISO 100 |
Standard exposure values for common shooting conditions at ISO 100. Use this to select a starting EV or verify your settings.
Frequently asked questions
What does EV mean in photography?
EV stands for Exposure Value. It is a dimensionless number that represents the total amount of light in a scene relative to a standard reference (f/1, 1 s, ISO 100). Each full EV step is one stop, meaning the light doubles or halves. Most outdoor scenes fall between EV 0 (dark night interior) and EV 16 (bright sunny beach). Your camera's light meter is essentially measuring EV and then choosing aperture and shutter combinations to match it.
How do I solve for aperture, shutter, or ISO instead of EV?
Use the "Solve for" dropdown at the top. Switch it to "Aperture," "Shutter Speed," or "ISO," then enter the target EV you want to achieve along with the two settings you already know. The calculator rearranges the EV formula and returns the missing value. For example, select "Shutter Speed" and set EV 15, f/8, ISO 100, and you will get 1/100 s as the answer.
What is an equivalent exposure?
An equivalent exposure is any combination of aperture, shutter speed, and ISO that produces the same EV as your current settings. For example, f/8 at 1/125 s is equivalent to f/5.6 at 1/250 s and to f/11 at 1/60 s (all at the same ISO). The brightness is identical; what changes is depth of field and motion blur. The steps panel lists several equivalents automatically from your inputs.
How many stops does an ND filter add?
Each full stop of ND doubles the required shutter time. A 3-stop ND multiplies shutter time by 8 (2^3), a 6-stop by 64, and a 10-stop by 1,024. So a 1/100 s exposure through a 10-stop ND becomes approximately 10 s. Enter the filter stop count into the ND Filter field and the calculator shows the compensated shutter duration automatically.
What is the reciprocal rule for hand-holding?
The reciprocal rule states that the slowest safe hand-held shutter speed is 1 divided by your effective focal length in millimetres. For a 50 mm lens that is 1/50 s, for a 200 mm telephoto it is 1/200 s. On a crop-sensor camera (e.g. APS-C with a 1.5x crop factor), multiply the focal length: a 50 mm lens behaves like 75 mm, so the minimum is 1/75 s. This is a guideline, not a guarantee; image-stabilised lenses and good technique can extend the limit by 2-4 stops.
What EV is considered correct exposure for portraits indoors?
Typical home or studio indoor lighting with soft lamps sits around EV 5 to 7. A well-lit studio with flash might reach EV 9 to 11 at the subject. For portrait work you often set your target EV based on the ambient light or flash output and then choose aperture for depth-of-field effect and ISO for noise control, letting the shutter fall where it may (or the other way around for freezing motion).
What is the Sunny 16 rule?
The Sunny 16 rule is a quick exposure guideline: in bright direct sunlight, set your aperture to f/16 and your shutter speed to 1/ISO s (so ISO 100 uses 1/100 s, ISO 200 uses 1/200 s). That gives roughly EV 15. From there you can open up for shade (EV 12), overcast (EV 11), or close down for beach or snow (EV 16). It is a sanity check, not a replacement for metering, but it is accurate within half a stop on a clear sunny day.