A log scale makes it easy to compare values that cover a large range, such as in this map
A logarithmic scale is a nonlinear scale used when there is a large range of quantities. Common uses include the earthquake strength, sound loudness, light intensity, and pH of solutions.
It is based on orders of magnitude, rather than a standard linear scale, so each mark on the scale is the previous mark multiplied by a value.
Contents

Common usages 1

Graphic representation 2

Log–log plots 2.1

Semi logarithmic plots 2.2

See also 3

Notes 4

References 5

External links 6
Common usages
The following are examples of commonly used logarithmic scales, where a larger quantity results in a higher value:
The following are examples of commonly used logarithmic scales, where a larger quantity results in a lower (or negative) value:
Some of our senses operate in a logarithmic fashion (Weber–Fechner law), which makes logarithmic scales for these input quantities especially appropriate. In particular our sense of hearing perceives equal ratios of frequencies as equal differences in pitch. In addition, studies of young children in an isolated tribe have shown logarithmic scales to be the most natural display of numbers by humans.^{[1]}
Graphic representation
The top left graph is linear in the X and Y axis, and the Yaxis ranges from 0 to 10. A base10 log scale is used for the Y axis of the bottom left graph, therefore the Y axis ranges from 0^{[note 1]} to 1,000.
The top right graph uses a log10 scale for just the X axis, and the bottom right graph uses a log10 scale for both the X axis and the Y axis.
Presentation of data on a logarithmic scale can be helpful when the data

Covers a large range of values, since the use of the logarithms of the values rather than the actual values reduces a wide range to a more manageable size

May contain exponential laws or power laws, since these will show up as straight lines
A slide rule has logarithmic scales, and nomograms often employ logarithmic scales. The geometric mean of two numbers is midway between the numbers. Before the advent of computer graphics, logarithmic graph paper was a commonly used scientific tool.
Log–log plots
Plot on log–log scale of equation F(x) = (x^{−10} )(10^{20}), which can be expressed as the line: log(F(x)) = −10 log(x) + 20.
If both the vertical and horizontal axis of a plot is scaled logarithmically, the plot is referred to as a log–log plot.
Semi logarithmic plots
If only the ordinate or abscissa is scaled logarithmically, the plot is referred to as a semi logarithmic plot.
See also
Notes

^ not exactly zero, but close enough for the purpose of this explanation
References

^ "Slide Rule Sense: Amazonian Indigenous Culture Demonstrates Universal Mapping Of Number Onto Space". ScienceDaily. 20080530. Retrieved 20080531.
Stanislas, Dehaene; Véronique Izard,

Why using logarithmic scale to display share prices? (English)

Example Logarithmic Graph Paper Template

Media related to at Wikimedia Commons
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