Unblinking Eye
                                        Logarithms
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Start with:  bx = y.

b = base
x = exponent
y = power

If the base and exponent are given we compute a power.
If the exponent and power are given we compute a root (or radical).
If the power and base are given, we compute a logarithm.

The logarithm of a number y with respect to a base b is the exponent to which b must be raised to obtain y.

 bx = y   or   x = log b y

Examples:

102 = 100         2 = log10 100
10-2 = 0.01          -2 = log10 0.01
100 = 1         0 = log10 1
23 = 8         3 = log2 8
32 = 9         2 = log3 9
25.5 = 5         .5 = log25 5
2.5 = 1.414          .5 = log2 1.414

The most important logarithms in photography are those of base b = 2.

Logarithms of base b = 10 are known as common logarithms.

Logarithms of base e = 2.71828 are known as natural logarithms. (E is the base of the natural logarithm function, derived from the series 2 + + 1/3 + + 1/5 )

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