:It is said in "Quantities of information" that "The choice of logarithmic base in the following formulae determines the unit of information entropy that is used." In computer science, log2 is the most natural logarithm. Similarly, in the case of the binary entropy function, you are most commonly interested in log2 since the function is the entropy of a value that can take only two values. However, the article could and probably should use the natural log all over.