Exposure Value is the unit that measures brightness, also referred to as a “stop.” While the term EV may not appear directly on your camera, it is relevant for your camera’s light meter and exposure compensation dial and ND filter.
Metering
When the pointer is in the middle at 0EV, it indicates the optimal exposure that the camera suggests. (you can disagree)
If your light meter shows -1EV, it means the camera suggests that it might be underexposed and you can increase the brightness by 1EV.
Equivalent Exposure Value
Different combinations of aperture, shutter speed and ISO can achieve the same EV. For instance-
A) f/1.4 1/500 ISO 100
B) f/8 1/125 ISO 800
These two settings are equivalent in EV. You can choose which combinations to use based on your creative decisions.
How to increase EV?
+1EV = increase by 1 stop
Aperture f/1.4 ← f/2 ← f/2.8 ← f/4 ← f/5.6 ← f/8 ← f/11 ← f/16 ← f/22
Shutter Speed 1/15 ← 1/30 ← 1/60 ← 1/125 ← 1/250 ← 1/500 ← 1/1000
ISO 100 → 200 → 400 → 800 → 1600 → 3200 → 6400
How to decrease EV?
-1EV = decrease by 1 stop
Aperture f/1.4 → f/2 → f/2.8 → f/4 → f/5.6 → f/8 → f/11 → f/16 → f/22
Shutter Speed 1/15 → 1/30 → 1/60 → 1/125 → 1/250 → 1/500 → 1/1000
ISO 100 ← 200 ← 400 ← 800 ← 1600 ← 3200 ← 6400
Exposure Compensation
The quickest way to increase or decrease EV is to use the exposure compensation dial in semi-auto mode (Program mode, Aperture Priority mode and Shutter Priority mode), so you don’t need to do any math.
+1EV = (Light) x 2 = brighter
+2EV = (Light) x 4 = brighter
Please note that in manual mode, the exposure compensation dial will not work unless the ISO is set to Auto.
Manual Mode
You have the flexibility to increase or decrease the exposure value (EV) by adjusting a combination of the aperture and shutter speed. For example, you can increase the aperture by 0.5 stops and adjust the shutter speed by 0.5 stops, depending on the situation.
ISO can be tricky; it doesn’t capture more light per se, but it amplifies the signal to make the image brighter.
Long Exposure & ND filter
EV is especially important when using neutral density (ND) filters. ND filters reduce the light entering the lens, allowing for longer exposures without overexposing the image.
To calculate which neutral density (ND) filter to use and the corresponding exposure settings, follow these steps:
1/ Identify the Desired Effect
Determine how much longer you want the exposure to last. If you aim to capture motion blur in water, clouds, or light trails, 30 seconds is a good starting point.
2/ Choose a ND Filter
Choose the ND filter based on how many stops you want to reduce the light.
ND filters are rated in stops. Each stop reduces light by half.
ND2 = 1 stop light reduction
ND4 = 2 stops light reduction
ND8 = 3 stops light reduction
ND1000 = 10 stops light reduction
When we talk about a 10-stop ND filter, it means only 1/1000th of the light gets through. 10-15 stop ND filters are commonly used in cloudscape and seascape long exposures.
3/ Calculate New Exposure Settings
Start with your current aperture, shutter speed, and ISO settings for a properly exposed image without a filter. You can do it with the camera’s metering.
For this demo, I’m using a free app on Android called “Light Meter.” If you’re on iOS, check out the Long Exposure Calculator app, or you can find it on PhotoPills. Apps will save you valuable time on location, allowing you to focus more on composition.
If you are confused about 1-stop and 2-stop etc., here is a useful website → Equivalent Exposure Calculator
You can compare 2 exposure settings and find out the difference.