Camera Exposure Calculator
One Number That Describes an Entire Exposure
Aperture, shutter speed, and ISO each affect exposure differently, but they can be collapsed into a single figure: exposure value, or EV. Two completely different combinations — f/2.8 at 1/500s, or f/11 at 1/30s — can produce the identical exposure and the identical EV. This calculator takes your actual settings and reduces them to an EV100 figure (exposure value normalized to ISO 100), which is what lets you compare exposures across different gear and lighting conditions on a common scale.
The Formula
EV100 = EV − log&sub2;(ISO / 100)
Here N is the aperture f-number, t is shutter speed in seconds, and the second line normalizes the raw EV to what it would be at ISO 100, since raising ISO effectively adds light-gathering sensitivity without changing the physical aperture or shutter.
Where This Calculation Matters
- Matching exposures across cameras — comparing EV100 lets you replicate a look shot on one body with a different lens or sensor on another.
- Manual exposure troubleshooting — when a meter reading looks wrong, computing EV from your actual settings checks the math independently.
- Studio and flash work — many flash meters and guide-number calculations are expressed in EV, so converting camera settings to EV keeps the two in sync.
- Learning the exposure triangle — seeing how a stop change in any one variable shifts EV builds intuition faster than adjusting settings by feel.
Typical EV100 Values by Lighting Condition
These are widely published rule-of-thumb figures used for manual exposure estimation, sometimes called the "Sunny 16" system:
| Condition | EV100 (approx.) |
|---|---|
| Bright sun, distinct shadows (Sunny 16: f/16 at 1/100s) | ~14.6 |
| Hazy sun, soft shadows | ~13–14 |
| Cloudy bright, no shadows | ~12–13 |
| Open shade / overcast | ~11–12 |
| Indoor, well-lit room | ~5–7 |
| Indoor, dim lighting | ~2–4 |
The Sunny 16 EV100 value of 14.6 shown above is computed directly from f/16 and 1/100s using this calculator's own formula, confirming the rule of thumb against the math.
How to Use This Calculator
- Enter the aperture as an f-number (for example, 2.8).
- Enter the shutter speed in seconds (for example, 0.008 for 1/125).
- Enter the ISO value.
- Select Calculate to get the EV100 figure.
Related Calculations
To find an equivalent exposure after changing ISO, use the ISO Exposure Calculator. For light gathered relative to sensor size, see the Camera Crop Factor Calculator.