EXPOSURE VALUE (EV)

A scale of numbers called Exposure Values (EV) identifies definite exposure settings, no matter what combination of aperture and shutter speed is used.

The practical EV range is from -5, to +20. If the exposure controls are set for EV -5, the light is very dim. At +20, the light is very bright. A change of one EV step, such as from EV 5 to EV 6, re­presents one standard exposure step.

Some camera manufacturers use EV numbers to specify the measuring range of the built-in exposure meter.

Find possible pairs of control settings in the accompanying EV table.

HOW TO READ THE EV TABLE
EV numbers run along the left, shutter speeds along the top, and f-stops are in the body.

Example: Find EV -6 at the left. Read across the table and note the shutter speeds at the top. This EV can be set three ways: f-2 at 4 minutes, f-1.4 at 2 minutes, f-1 at 1 minute.

Example: Find EV 18 on the left.  It can be set six ways including f-64 at 1/60 and f-11 at 1/2000.

The Basis of EV Numbers - The number assigned to each exposure step is arbitrary. EV 0 is f-1 at 1 second, which is easy to remember.

For Math Fans:

EV = 3.3 Log10 (f˛/T)

f  is f-stop
T is exposure time

The Sunny 16 rule: 
EV15 (Bright or Hazy Sun Distinct Shadows) at ISO 100

 

EV NUMBERS & EQUIVALENT EXPOSURE SETTINGS
SHUTTER SPEED
EV 4
Min.		 2
Min.		 1
Min.		 30
Sec.		 15 8 4 2 1 1/2 1/4 1/8 1/15 1/30 1/60 1/125 1/250 1/500 1/1000 1/2000
-8
-7
-6		 f-1
1.4
2
f-1
1.4

f-1		                           EV = 3.3 Log10 (f˛/T)  
-5
-4
-3		 2.8
4
5.6		 2
2.8
4		 1.4
2
2.8		 f-1
1.4
2
f-1
1.4

f-1		                      
-2
-1
0		 8
11
16		 5.6
8
11		 4
5.6
8		 2.8
4
5.6		 2
2.8
4		 1.4
2
2.8		 f-1
1.4
2
f-1
1.4

f-1		                      
1
2
3		 22
32
45		 16
22
32		 11
16
22		 8
11
16		 5.6
8
11		 4
5.6
8		 2.8
4
5.6		 2
2.8
4		 1.4
2
2.8		 f-1
1.4
2
f-1
1.4

f-1		                
4
5
6		 64

 45
64
 32
45
64		 22
32
45		 16
22
32		 11
16
22		 8
11
16		 5.6
8
11		 4
5.6
8		 2.8
4
5.6		 2
2.8
4		 1.4
2
2.8		 f-1
1.4
2
f-1
1.4

f-1		          
7
8
9		       64

 45
64
 32
45
64		 22
32
45		 16
22
32		 11
16
22		 8
11
16		 5.6
8
11		 4
5.6
8		 2.8
4
5.6		 2
2.8
4		 1.4
2
2.8		 f-1
1.4
2
f-1
1.4

f-1		    
10
11
12		             64

 45
64
 32
45
64		 22
32
45		 16
22
32		 11
16
22		 8
11
16		 5.6
8
11		 4
5.6
8		 2.8
4
5.6		 2
2.8
4		 1.4
2
2.8		 f-1
1.4
2
f-1
1.4
13
14
15		                   64

 45
64
 32
45
64		 22
32
45		 16
22
32		 11
16
22		 8
11
16		 5.6
8
11		 4
5.6
8		 2.8
4
5.6		 2
2.8
4
16
17
18		                         64

 45
64
 32
45
64		 22
32
45		 16
22
32		 11
16
22		 8
11
16		 5.6
8
11
19
20
                               64

 45
64
 32
45
 22
32
 16
22