Photography light calculator

The combination of shutter speed, aperture and film speed/ISO (and light modifiers) are expressed as EV or "Exposure Value". This number depends on the amount of light present in a scene, either natural light (sun/moon) or artificial (strobe/lamp). A difference of 1 in EV corresponds to 1 "stop" (+1 stop = 2 x more light). This calculation is valid for both analog and digital photography
A ND (neutral density) filter is a piece of glass you can mount on a lens that attenuates the light without influencing the colors

Camera settings

Aperture: f/2.8 - wide aperture, possibly a zoom

Shutter: 0.01667 sec - medium exposure, good for flash photography

ISO: 640 ASA - low ISO, little noise

Scene lighting: EV6.2

-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
starlight to dim ambient lightmoon eclipse to night home interiorneon lights to landscape after sunsetbright light to weak sunbright daylight to direct sunlight
  • Pure Exposure Value: EV100 = 8.88 (based on shutter & aperture)
  • APEX Exposure Value: EV640 = 6.2 (based on shutter, aperture, ISO)
  • Luminance: 9.19 cd/m² = 0.85 cd/ft²
  • Luminance: 2.68 ftL (foot Lambert)
  • Illuminance: 183.8 lux
  • Illuminance: 17.07 fc (foot-candle)

Explanation

EV is an estimation of how much light you need for a decent photo with these settings. If you use camera settings for EV10 and you actually have EV15 in your scene, your photo will be overexposed. If you use camera settings for EV10 but you only have EV3 light in your scene, your photo will be underexposed.

Examples

Definition of EV: 1s at f/1.0: EV0
Sunny 16 Rule: EV15
Shooting film in broad daylight: EV12
Extreme ISO in e.g. a bar at night: EV0
Long exposure in broad daylight: EV12

References

Exposure value
Scantips: Exposure Value (photography)
The ultimate exposure computer

Frequently Asked Questions

What is Exposure Value (EV) in photography?

EV is a number representing a combination of aperture and shutter speed. EV 0 = 1 second at f/1.0. Each +1 EV halves the light (one stop). Sunny day = EV 15, indoor lighting = EV 7-8, night = EV 0 or below.

What is the Sunny 16 rule?

On a sunny day, use f/16 aperture with shutter speed = 1/ISO. At ISO 100: f/16, 1/100s. This equals EV 15. Cloudy = open 1-2 stops (f/8-f/11). Overcast = open 3 stops (f/5.6). Shade = open 4 stops (f/4).

How does ISO affect exposure?

Doubling ISO = +1 stop of light sensitivity (halve the light needed). ISO 100→200 lets you use faster shutter or smaller aperture. Trade-off: higher ISO = more noise. Modern cameras handle ISO 1600-6400 well; older cameras show noise above ISO 800.

When should I use an ND filter?

Use ND filters to reduce light for: long exposures in daylight (waterfalls, clouds), wide apertures in bright light (shallow depth of field), video at 180° shutter rule. A 3-stop ND lets you shoot at 1/30s instead of 1/250s in sunlight.