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The PhotoNotes.org Dictionary of Film and Digital Photography.

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Exposure value (EV).

The amount of light hitting the surface of a photosensitive material based on a combination of shutter speed and aperture values. EV 0 is the combination of a 1 second exposure at f/1.

The law of reciprocity states that the relationship between shutter speed and aperture is proportional, and so simple tables of exposure values can easily be calculated, as shown below. For more discussion on this topic, see the section on the law of reciprocity.

 
f/1.0
1.4
2.0
2.8
4.0
5.6
8.0
11
16
22
32
45
64
1 sec
0
1
2
3
4
5
6
7
8
9
10
11
12
1/2
1
2
3
4
5
6
7
8
9
10
11
12
13
1/4
2
3
4
5
6
7
8
9
10
11
12
13
14
1/8
3
4
5
6
7
8
9
10
11
12
13
14
15
1/15
4
5
6
7
8
9
10
11
12
13
14
15
16
1/30
5
6
7
8
9
10
11
12
13
14
15
16
17
1/60
6
7
8
9
10
11
12
13
14
15
16
17
18
1/125
7
8
9
10
11
12
13
14
15
16
17
18
19
1/250
8
9
10
11
12
13
14
15
16
17
18
19
20
1/500
9
10
11
12
13
14
15
16
17
18
19
20
21
1/1000
10
11
12
13
14
15
16
17
18
19
20
21
22
1/2000
11
12
13
14
15
16
17
18
19
20
21
22
23
1/4000
12
13
14
15
16
17
18
19
20
21
22
23
24

Exposure value table: shutter speed in seconds on the vertical axis and lens aperture in f/stops on the horizontal axis.

Note that the aperture range goes from f/1 to f/64. Lenses with apertures of less than f/1 have been built but are extremely unusual - f/1 is the typical largest aperture of a fast (low light) lens. 35mm camera lenses rarely stop down beyond about f/22 or so - smaller f-stop values such as f/64 are seen typically with view cameras. Time values of longer than 1 second result in negative EV values.

A table like this looks rather daunting, but EV is actually a very useful concept. By memorizing a handful of EV numbers you can take photographs fairly reliably under certain lighting conditions without a light meter. For example, if you’re using ISO 100 film then these values are handy:

EV 15 - direct sunlight.
EV 12 - open shade on a sunny day.
EV 7 - typical indoor lighting in offices, etc.

cf. aperture, f stop, reciprocity, reciprocity failure, shutter speed.

Entry last updated 2002-04-05. Term 428 of 1487.


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