Back in the 2000’s, when I was learning about how to use a camera I found a website, fredparker.com. It had a section called “The Ultimate Exposure Computer”. That resource alone contributed to most of my understanding of exposure in photography. Sadly, Fred Parker passed away and the website disappeared but it was such an important resource I had to put what I could back for others to use. The text below is some of what I learned from Fred’s Ultimate Exposure Computer.
Exposure values represent a combination of a camera‘s shutter speed and f-number, such that all combinations that yield the same exposure have the same EV. Each value can be assigned to a type of brightness one might experience in a variety of situations. The values are relative to each other and was developed to reduce typical camera settings to a single value reference. EV tables are usually, but not always, calculated for an ISO of 100. The notation for this is EV100.
Exposure Value Chart
| EV100 | Lighting situation |
|---|---|
| -6 | Night, away from city lights, subject under starlight only. |
| -5 | Night, away from city lights, subject under crescent moon. |
| -4 | Night, away from city lights, subject under half moon. Meteors (during showers, with time exposure). |
| -3 | Night, away from city lights, subject under full moon. |
| -2 | Night, away from city lights, snowscape under full moon. |
| -1 | Subjects lit by dim ambient artificial light. |
| 0 | Subjects lit by dim ambient artificial light. |
| 1 | Distant view of lighted skyline. |
| 2 | Lightning (with time exposure). Total eclipse of moon. |
| 3 | Fireworks (with time exposure). |
| 4 | Candle lit close-ups. Christmas lights, floodlit buildings, fountains, and monuments. Subjects under bright street lamps. |
| 5 | Night home interiors, average light. School or church auditoriums. Subjects lit by campfires or bonfires. |
| 6 | Brightly lit home interiors at night. Fairs, amusement parks. |
| 7 | Bottom of rainforest canopy. Brightly lighted night-time streets. Indoor sports. Stage shows, circuses. |
| 8 | Las Vegas or Times Square at night. Store windows. Campfires, bonfires, burning buildings. Ice shows, football, baseball etc. at night. Interiors with bright florescent lights. |
| 9 | Landscapes, city skylines 10 minutes after sunset. Neon lights, spotlighted subjects. |
| 10 | Landscapes and skylines immediately after sunset. Crescent moon (long lens). |
| 11 | Sunsets. Subjects in deep shade. |
| 12 | Half moon (long lens). Subject in open shade or heavy overcast. |
| 13 | Gibbous moon (long lens). Subjects in cloudy-bright light (no shadows). |
| 14 | Full moon (long lens). Subjects in weak, hazy sun. |
| 15 | Subjects in bright or hazy sun (Sunny f/16 rule). |
| 16 | Subjects in bright daylight on sand or snow. |
| 17 | Rarely encountered in nature. Some man made lighting. |
| 18 | Rarely encountered in nature. Some man made lighting. |
| 19 | Rarely encountered in nature. Some man made lighting. |
| 20 | Rarely encountered in nature. Some man made lighting. |
| 21 | Rarely encountered in nature. Some man made lighting. |
| 22 | Extremely bright. Rarely encountered in nature. |
| 23 | Extremely bright. Rarely encountered in nature. |
Each of these values are one stop brighter than the previous, and one stop darker than the next.
Before we jump into the next bit here’s a quick reference on aperture, shutter and ISO as full stops for the most common settings.
- ISO: 25, 50, 100, 200, 400, 800, 1600, 3200, 6400
- Shutter: 1s, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250,
- Aperture: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22,
How to translate this to your camera settings
The simplest way to use this information is to use the “sunny 16” rule as an anchor and transpose that into the scene you are about to photograph.
The sunny 16 rule states that if you are photographing a scene on a bright sunny day then you will achieve a good exposure using IS0 100, 1/125sec shutter speed and f/16 aperture.
Within the chart EV 15 is where the sunny 16 rule sits. EV 15 is a bright sunny day. Knowing that means you have a point of reference for all other scenes. When you are photographing a scene which isn’t a sunny day then you can check the EV chart, find the scene most like the one you want to photograph and then adjust your settings to suit.
Lets say that your day is overcast. To calculate your exposure, start at EV15 and work back through the chart to EV 12, which is the brightness of an overcast day. EV 12 is 3 stops darker than EV 15 so we can adjust any of the 3 exposure settings on our camera to compensate from our reference point of ISO 100, 1/125, f/16:
- ISO 800, 1/125, f16
- ISO 100, 1/125, f5.6
- ISO 100, 1/15, f16
The setting you choose will be based on your limitations in the field and the constraints of the scene/subject. Typically when shooting with film ISO is fixed so the only variables one can consider are shutter and or aperture.
It should be noted that the values for direct sunlight apply between approximately two hours after sunrise and two hours before sunset, and assume front lighting. As a rough general rule, decrease EV by 1 for side lighting, and decrease EV by 2 for back lighting.