For those who felt a sinking feeling in the pit of the stomach when they saw the expression log24096, here is a quick review. For example, in the shocked movie above, if you change the input to 4096, then your output should be 12.0. So play around. What's the output if the input is 32? 8? 2? 1?
 How to compute: log2 X = (ln X)/(ln 2), where "ln" is the natural log function. Find it on your Calculator.
Each of those inputs is a perfect power of 2, so the answers are nice integers. For a number like 203 = 8000, the ouput is not a perfect integer. (Note: I use 20 here since that is the number of amino acids, so numbers like 203 will be important in what follows.) (Also note: log2(0) = -infinity, which is denoted "-inf" above.)
The logarithm review above was created for the section on Information Theory in the genome site, hence the concentration on logs to the base 2. Still it gives a nice review of what logs are all about. If you got here by opening a separate window, then just click the window closed to leave.