Introduction
There is a misconception about exposure value (EV) and light value (LV), as they are used to mean the same thing. Both refer to the amount of light, and here is the catch, LV in simple terms is the amount of light reflected off of subjects within a scene (how luminant a scene is), and EV is the amount of light captured with your camera (of course it is affected by LV among other factors).
We can see how those affect the quality of headshots, as lighting is essential when taking a great headshot. Now, let's delve into more details to better use LV and EV to our advantage.
Sunny 16 Rule
We've mentioned that LV has an effect on EV settings of your camera, so you need a way of measuring LV in the scene, but you don't need a fancy light meter for that purpose, you can use Sunny 16 Rule.
The rule estimates LV based on simple observations. Hence, it can be directly translated to an EV setting (lens opening), based on a fixed ISO value.
Look at the shadows on subjects, and observe how dark they are. Also, how sharp shadows' edges are, and with that you can estimate LV and set the EV accordingly.
The rule says: On a sunny day, set the aperture to f/16 and shutter speed to 1/[your ISO setting], for subjects in direct sunlight.
A translation for this sentence: Consider you are using ISO of 200, and shooting a headshot in direct sunlight, your EV should be set to f/16, and your shutter speed should be 1/180th of a second; because it is the closest to 1/200 (1/ISO).
For Other Lighting Conditions
It is not a rule if it doesn't work for different lighting conditions, and for that you can use this table.
| Light Conditions | Shadows | Exposure |
|---|---|---|
| Snow / Sand | Dark with sharp edges | f/22 |
| Sunny | Distinct | f/16 |
| Slightly overcast | Bright with fuzzy edges | f/11 |
| Overcast | Barely visible | f/8 |
| Heavy overcast | Absent | f/5.6 |
| Open shade | Absent | f/4 |
| Backlighting | - | f/2.8 |
When is Sunny 16 Rule Good?
Well, if you are willing to randomly set the ISO, and you'll accept whatever EV setting it gives you. Keep on reading to know why you don't want that.
ISO
ISO is a standard measurement of light sensitivity. In simple terms, it tells how much your sensor is able to capture variability in light values, regardless of other settings. The higher the value the more sensitive to light the sensor is.
Another useful notion for ISO is that it works as a middle man between the outside world and your camera, in regards to light. So, it is a bridge between LV and EV.
The Zero Point
The light value of a dim interior is set to 0. If we need the same exposure value in our headshot in this setting, we have to set the ISO of the camera to ISO 100.
And for ISO 100, light value maps to the same exposure value. So according to what we've discussed in Sunny 16; we can vary the ISO to control our f-stop, as it also has an effect on the depth of field for our headshot.
Now, we know how much light we can let in using ISO. And although we can effectively vary the EV setting of our camera using the same ISO every time, but that changes the depth of field for our headshot (how much of the background and foreground is sharp in contrast to how much of that is blurry).
And to take a great headshot we need to take all of that into account.
Determining Exposure Value Accurately
We need two charts, one for LV, the other for EV. The light value chart is used to map the observations we made in the Sunny 16 Rule to a light value (a number).
We want to have the same number as an exposure value, so we can use the second chart to find a suitable EV setting.
Light Value Chart
- Light Value
- Lighting condition: similar to the one we saw in Sunny 16 Rule.
| LV Value | Subject |
|---|---|
| 18 | - Bright reflections - Sand - Snow |
| 17 | - White or very light colored/toned subject in bright sunlight |
| 16 | |
| 15 | - Subject is medium colored/toned in bright sunlight |
| 14 | - Slightly overcast |
| 13 | - Overcast |
| 12 | - Heavy overcast |
| 11 | - Sunset - Open shade |
| 10 | - Landscapes just after sunset or before sunrise |
| 9 | - Landscapes 10 minutes after sunset/before sunrise - Neon and lighted signs at night - Stage shows with bright lighting |
| 8 | - Times Square at night - Store windows at night - Fires at night - Stadium lighting - Interior with sunlight coming through window - Interior with many florescent lights |
| 7 | - Bright street at night - Stage shows with average lighting - Daytime interior with skylight |
| 6 | - Fairs and amusement parks at night - Daytime interior with windows & no direct sunlight |
| 5 | - Night interior with bright lighting |
| 4 | - Floodlighted buildings, monuments, fountains - Holiday lighting at night (indoor or outdoor) - Night interior with average lighting - Candle-lighted close-ups |
| 3 | - Street at night |
| 2 | |
| 1 | |
| 0 | - Dim interior |
| -1 | |
| -2 | |
| -3 | - Rural landscape illuminated by a full moon |
| -4 | |
| -5 | |
| -6 | - Rural landscape illuminated by starlight |
Exposure Value Chart
This chart can be somewhat tricky to read, as it contains ISO and EV on the left side, and the f-stop and shutter speed on the right side.
| Exposure Value Numbers | Exposure Settings | |||||||||||||
| 100 | 200 | 400 | 800 | 1600 | f/1 | f/1.4 | f/2 | f/2.8 | f/4 | f/5.6 | f/8 | f/11 | f/16 | f/22 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| - | - | - | - | 18 | - | - | - | - | - | - | - | - | - | 8000 |
| - | - | - | 18 | 17 | - | - | - | - | - | - | - | - | 8000 | 4000 |
| - | - | 18 | 17 | 16 | - | - | - | - | - | - | - | 8000 | 4000 | 2000 |
| - | 18 | 17 | 16 | 15 | - | - | - | - | - | - | 8000 | 4000 | 2000 | 1000 |
| 18 | 17 | 16 | 15 | 14 | - | - | - | - | - | 8000 | 4000 | 2000 | 1000 | 500 |
| 17 | 16 | 15 | 14 | 13 | - | - | - | - | 8000 | 4000 | 2000 | 1000 | 500 | 250 |
| 16 | 15 | 14 | 13 | 12 | - | - | - | 8000 | 4000 | 2000 | 1000 | 500 | 250 | 125 |
| 15 | 14 | 13 | 12 | 11 | - | - | 8000 | 4000 | 2000 | 1000 | 500 | 250 | 125 | 60 |
| 14 | 13 | 12 | 11 | 10 | - | 8000 | 4000 | 2000 | 1000 | 500 | 250 | 125 | 60 | 30 |
| 13 | 12 | 11 | 10 | 9 | 8000 | 4000 | 2000 | 1000 | 500 | 250 | 125 | 60 | 30 | 15 |
| 12 | 11 | 10 | 9 | 8 | 4000 | 2000 | 1000 | 500 | 250 | 125 | 60 | 30 | 15 | 8 |
| 11 | 10 | 9 | 8 | 7 | 2000 | 1000 | 500 | 250 | 125 | 60 | 30 | 15 | 8 | 4 |
| 10 | 9 | 8 | 7 | 6 | 1000 | 500 | 250 | 125 | 60 | 30 | 15 | 8 | 4 | 2 |
| 9 | 8 | 7 | 6 | 5 | 500 | 250 | 125 | 60 | 30 | 15 | 8 | 4 | 2 | 1" |
| 8 | 7 | 6 | 5 | 4 | 250 | 125 | 60 | 30 | 15 | 8 | 4 | 2 | 1" | 2" |
| 7 | 6 | 5 | 4 | 3 | 125 | 60 | 30 | 15 | 8 | 4 | 2 | 1" | 2" | 4" |
| 6 | 5 | 4 | 3 | 2 | 60 | 30 | 15 | 8 | 4 | 2 | 1" | 2" | 4" | 8" |
| 5 | 4 | 3 | 2 | 1 | 30 | 15 | 8 | 4 | 2 | 1" | 2" | 4" | 8" | 15" |
| 4 | 3 | 2 | 1 | 0 | 15 | 8 | 4 | 2 | 1" | 2" | 4" | 8" | 15" | 30" |
| 3 | 2 | 1 | 0 | -1 | 8 | 4 | 2 | 1" | 2" | 4" | 8" | 15" | 30" | - |
| 2 | 1 | 0 | -1 | -2 | 4 | 2 | 1" | 2" | 4" | 8" | 15" | 30" | - | - |
| 1 | 0 | -1 | -2 | -3 | 2 | 1" | 2" | 4" | 8" | 15" | 30" | - | - | - |
| 0 | -1 | -2 | -3 | -4 | 1" | 2" | 4" | 8" | 15" | 30" | - | - | - | - |
| -1 | -2 | -3 | -4 | -5 | 2" | 4" | 8" | 15" | 30" | - | - | - | - | - |
| -2 | -3 | -4 | -5 | -6 | 4" | 8" | 15" | 30" | - | - | - | - | - | - |
| -3 | -4 | -5 | -6 | - | 8" | 15" | 30" | - | - | - | - | - | - | - |
| -4 | -5 | -6 | - | - | 15" | 30" | - | - | - | - | - | - | - | - |
| -5 | -6 | - | - | - | 30" | - | - | - | - | - | - | - | - | - |
| -6 | - | - | - | - | 60" | - | - | - | - | - | - | - | - | - |
Example
Conisder that you've set the ISO to 400, and you are taking a headshot in a well-lit interior, so we can go to the LV chart to find a suitable LV number from that chart. We need to get some EV settings to get to a value that matches the LV of our interior.
First, we go to the LV chart to get the light value for a well-lit interior. Light value for this lies some where between 10 to 12, it is up to you to determine which value fits your setting.
| LV Value | Subject |
|---|---|
| 12 | - Heavy overcast |
| 11 | - Sunset - Open shade |
| 10 | - Landscapes just after sunset or before sunrise |
Anyway, let's consider it is 11, with information in hand we can go to the second chart. And within the ISO 400 column, we search for an EV of 11.
| 100 | 200 | 400 | 800 | 1600 | f/1 | f/1.4 | f/2 | f/2.8 | f/4 | f/5.6 | f/8 | f/11 | f/16 | f/22 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 13 | 12 | 11 | 10 | 9 | 8000 | 4000 | 2000 | 1000 | 500 | 250 | 125 | 60 | 30 | 15 |
Now we found the row that will give you the same EV for your selected ISO. That means you can set the f-stop to f/8 and a shutter speed of 125 or 1/125th of a second. Or any other combination, that gives you greater freedom to choose a suitable f-stop and shutter speed, based on other things you want to achieve in your headshot.
As we said, f-stop value affects the DOF, which in turn affects sharpness of background and foreground subjects in your headshot. And shutter speed affects the blurriness of moving objects. Typically, it won't be a huge factor, since we are shooting a steady headshot.
Conclusion
We hope you gained some insights into LV and EV, just as a reacp, LV is all about the amount of light present in the setting in which you are taking the shot. While EV is a gauge of how much of that is going into your sensor.