When this is done, the shape of the equation as displayed in the graph changes. The Y-axis has a minimum value of 1 rather than 0 which would be more normal for a graph like this. This peculiarity of log plots with variable values near 0 will be discussed in detail below. Log paper looks different than regular graph paper and the axes are labeled differently than regular paper. Semi log paper is used to plot a function where only one axis represents the log of a variable.
Log paper differs in two primary ways from regular graph paper.
Examine the logarithmic axes in the two figures above. Each axis has evenly spaced major grid lines labeled as powers of 10. The key to understanding the rather bizarre labeling and tic spacing of log paper is simply to understand how the log base 10 function works. First, the log of any power of 10, is simply the exponent of the power of 10. To compute the log of any other number that is not an exact power of 10, first write the number in scientific notation, then use the rule for computing the logarithm of products which says the log of a product is the sum of the logs .