Neil Schemenauer's Web Log

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March 18, 2006

Exposure table for a Canon A520

I plan to play around with the manual modes of my new A520. To help, I wrote a little Python program that generated the following table. The main formula is shutter time = aperture2 / 2EV. This table should appeal to programmers (even more so if the aperture values were not rounded off).

.----------- EV -------------.  .---------------------------- Shutter Speed --------------------------------.
ISO50   ISO100  ISO200  ISO400  f/2.6   f/3.2   f/3.5   f/4.0   f/4.5   f/5.0   f/5.6   f/6.3   f/7.1   f/8.0
0       -1      -2      -3      14      20      25      32      41      50      63      79      101     128
1       0       -1      -2      6.8     10      12      16      20      25      31      40      50      64
2       1       0       -1      3.4     5.1     6.1     8.0     10      13      16      20      25      32
3       2       1       0       1.7     2.6     3.1     4.0     5.1     6.2     7.8     9.9     13      16
4       3       2       1       0.8     1.3     1.5     2.0     2.5     3.1     3.9     5.0     6.3     8.0
5       4       3       2       1/2     0.6     0.8     1.0     1.3     1.6     2.0     2.5     3.2     4.0
6       5       4       3       1/5     1/3     1/3     0.5     0.6     0.8     1.0     1.2     1.6     2.0
7       6       5       4       1/9     1/6     1/5     1/4     1/3     1/3     1/2     0.6     0.8     1.0
8       7       6       5       1/19    1/12    1/10    1/8     1/6     1/5     1/4     1/3     1/3     0.5
9       8       7       6       1/38    1/25    1/21    1/16    1/13    1/10    1/8     1/6     1/5     1/4
10      9       8       7       1/76    1/50    1/42    1/32    1/25    1/20    1/16    1/13    1/10    1/8
11      10      9       8       1/151   1/100   1/84    1/64    1/51    1/41    1/33    1/26    1/20    1/16
12      11      10      9       1/303   1/200   1/167   1/128   1/101   1/82    1/65    1/52    1/41    1/32
13      12      11      10      1/606   1/400   1/334   1/256   1/202   1/164   1/131   1/103   1/81    1/64
14      13      12      11      1/1212  1/800   1/669   1/512   1/405   1/328   1/261   1/206   1/163   1/128
15      14      13      12      1/2424  1/1600  1/1337  1/1024  1/809   1/655   1/522   1/413   1/325   1/256
16      15      14      13      1/4847  1/3200  1/2675  1/2048  1/1618  1/1311  1/1045  1/826   1/650   1/512
17      16      15      14      1/9695  1/6400  1/5350  1/4096  1/3236  1/2621  1/2090  1/1651  1/1300  1/1024

LV
-5  Scene lit by the full moon
-4
-3
-2
-1
 0  Defined as light requiring 1 second exposure at f/1 and ISO100
 1  Dark scenes outdoors at night
 2  Typical night street scenes
 3  Brightly lit night street scenes
 4
 5
 6
 7  Typical indoors; light outdoors about 10 minutes after sunset
 8
 9
10  Dark, dreary overcast day in Boston, London or Paris
11
12  California bright overcast
13  Typical shadow cast in a daylight scene; cloudy bright days
14  Typical light level for side-lit daylight shots in good afternoon light
15  Gray card in full sunlight
16  Light gray object or skin in full sunlight
17  White object in full sunlight

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