Exposure Value (EV) Chart for Film and Video
Updated
The EV formula, EV charts for stills shutter speeds and for cinema frame rates and shutter angles, how ISO shifts EV, and how to turn a meter's EV reading into a T-stop.
- Exposure Value
- EV Chart
- Light Meter
- Exposure
On this page
What EV measures
Exposure value is one number for every combination of stop and exposure time that lets in the same amount of light. f/4 at 1/60 and f/2.8 at 1/120 are both about EV 9.9: one stop wider, one stop shorter. Each step of 1 EV is one stop.
The numbering runs the opposite way to what many people expect. A higher EV setting lets in less light, so bright scenes call for high EVs and dim ones for low EVs. Light meters, especially spot meters, can display a reading as an EV, and EV is a handy way to talk about a scene's brightness without fixing the stop or the shutter.
The formula
EV = log₂(N² ÷ t)N squared because the light through the lens goes with the area of the aperture. The formula ignores ISO: it describes the camera setting, not the scene.
Where
- N
- f-number or T-stop
- t
- Exposure time(s)
Example: f/4 at 1/60 second
- Calculation:
- log₂(4² × 60) = log₂(960)
- Result:
- EV 9.9
N = √(t × 2^EV)The same formula turned round: the stop that gives a particular EV at a particular exposure time.
Where
- EV
- Exposure value
- t
- Exposure time(s)
Example: EV 12 at 1/48 second
- Calculation:
- √(2¹² ÷ 48) = √85.3 = 9.24
- Result:
- f/9, a third of a stop past f/8
EV chart: f-stop and shutter speed
EV for the marked f-numbers and shutter speeds. The marked values are rounded (f/11 is really 11.31 and 1/60 stands in for 1/64), so the results land on tenths rather than whole numbers, which is how they come out on a meter too.
| Shutter | f/1.4 | f/2 | f/2.8 | f/4 | f/5.6 | f/8 | f/11 | f/16 | f/22 |
|---|---|---|---|---|---|---|---|---|---|
| 1/30 | 5.9 | 6.9 | 7.9 | 8.9 | 9.9 | 10.9 | 11.8 | 12.9 | 13.8 |
| 1/60 | 6.9 | 7.9 | 8.9 | 9.9 | 10.9 | 11.9 | 12.8 | 13.9 | 14.8 |
| 1/125 | 7.9 | 9.0 | 9.9 | 11.0 | 11.9 | 13.0 | 13.9 | 15.0 | 15.9 |
| 1/250 | 8.9 | 10.0 | 10.9 | 12.0 | 12.9 | 14.0 | 14.9 | 16.0 | 16.9 |
| 1/500 | 9.9 | 11.0 | 11.9 | 13.0 | 13.9 | 15.0 | 15.9 | 17.0 | 17.9 |
| 1/1000 | 10.9 | 12.0 | 12.9 | 14.0 | 14.9 | 16.0 | 16.9 | 18.0 | 18.9 |
EV chart for cinema settings
The same chart with the exposure time set by frame rate and shutter angle (time = angle ÷ (360 × frame rate)). Use the T-stop: it is what sets exposure on a cine lens.
| Frame rate and shutter | Time | T1.4 | T2 | T2.8 | T4 | T5.6 | T8 | T11 | T16 |
|---|---|---|---|---|---|---|---|---|---|
| 24 fps, 180° | 1/48 | 6.6 | 7.6 | 8.6 | 9.6 | 10.6 | 11.6 | 12.5 | 13.6 |
| 24 fps, 172.8° / 25 fps, 180° | 1/50 | 6.6 | 7.6 | 8.6 | 9.6 | 10.6 | 11.6 | 12.6 | 13.6 |
| 30 fps, 180° | 1/60 | 6.9 | 7.9 | 8.9 | 9.9 | 10.9 | 11.9 | 12.8 | 13.9 |
| 24 fps, 90° / 48 fps, 180° | 1/96 | 7.6 | 8.6 | 9.6 | 10.6 | 11.6 | 12.6 | 13.5 | 14.6 |
| 60 fps, 180° | 1/120 | 7.9 | 8.9 | 9.9 | 10.9 | 11.9 | 12.9 | 13.8 | 14.9 |
| 120 fps, 180° | 1/240 | 8.9 | 9.9 | 10.9 | 11.9 | 12.9 | 13.9 | 14.8 | 15.9 |
Two things stand out. 1/48 and 1/50 are within 0.06 EV of each other, so a 172.8° flicker-free shutter costs almost nothing. And every doubling of the frame rate at a fixed angle adds 1 EV, which is the stop you lose shooting high speed.
EV and ISO
A meter reading in EV is normally given at ISO 100 (written EV₁₀₀). At a higher ISO or EI the same scene needs a higher EV setting, because the camera needs less light: one EV more per doubling.
EV setting = EV₁₀₀ + log₂(ISO ÷ 100)Add this to the ISO 100 reading to get the EV your stop and shutter should make.
Where
- EV₁₀₀
- Meter reading at ISO 100
- ISO
- Camera ISO or EI
Example: EV₁₀₀ 12 at EI 800
- Calculation:
- 12 + log₂(800 ÷ 100) = 12 + 3
- Result:
- Set EV 15
| ISO / EI | 100 | 200 | 400 | 640 | 800 | 1280 | 1600 | 3200 | 6400 |
|---|---|---|---|---|---|---|---|---|---|
| Add to EV₁₀₀ | 0 | +1 | +2 | +2⅔ | +3 | +3⅔ | +4 | +5 | +6 |
From an EV reading to a T-stop
A stills meter or app that gives EV is still useful on a cinema set. Add the ISO offset, then solve for the stop at your exposure time. If the stop comes out narrower than you want, the difference is your ND.
Case study
Bright overcast exterior
Scenario
A spot meter on a gray card reads EV₁₀₀ 12. The camera is at EI 800, 24 fps, 180° (1/48 second), and the DP wants to shoot around T3.2.
Challenge
Find the stop the reading calls for, and the ND that brings it to T3.2.
Solution
- Add the ISO offset to the reading.
- Solve N = √(t × 2^EV) at 1/48 second.
- Work out the stops between that and the target, and convert to ND.
The numbers
EV setting = 12 + log₂(800 ÷ 100) = 15N = √(2¹⁵ ÷ 48) = √682.7 = 26.1With 6 stops of ND (ND 1.8): 26.1 ÷ 2³ = 3.27
Result
ND 1.8 at T3.2 (the exact answer, T3.27, is less than a tenth of a stop away).
Key takeaways
- Every 2 stops of ND halves the stop number, because N goes with the square root of the light.
- A reading that calls for f/26 at EI 800 and 1/48 is your cue that heavy ND is coming.
Sunny 16 as a check
The old stills rule of thumb says that in direct sun, f/16 at a shutter speed of 1/ISO gives a usable exposure. At ISO 100 that is f/16 at 1/100, about EV₁₀₀ 14.6. It is a rough check, not a meter, but it tells you quickly how much ND a sunny exterior needs.
At EI 800 the rule gives f/16 at 1/800. A cinema camera at 24 fps and 180° is at 1/48, 4.06 stops more exposure, and opening from f/16 to T2.8 adds 5.03 more: about 9 stops in all, or ND 2.7. That is why a day exterior at a wide stop goes through a lot of filtration, and why the internal ND alone often is not enough.
- Shutter: log₂(800 ÷ 48) = 4.06 stops
- Stop: 2 × log₂(16 ÷ 2.8) = 5.03 stops
- ND needed: 9.09 stops ≈ ND 2.7
Next steps
- Turn a change in EV into a T-stop, shutter angle, ISO or ND with the free exposure calculator, in your browser.
- Look up any density in the ND filter chart.
- See how stop, shutter, EI and ND trade off in the exposure triangle guide.
- Convert any shutter angle to a time in the shutter angle chart.
Once the exposure is set, a change of 1 EV is a change of one stop, and CineMath's free Exposure calculator takes it from there: enter the change and it gives the T-stop, shutter angle, ISO or ND that compensates.