A method of improving geological log data obtained from use of one or more logging tools, the method including the steps of (i) from raw log data recorded by the said one or more logging tools, respectively deriving according to differing first and second derivation methods a first log data set and a corresponding second log data set having the same vertical response attribute, (ii) mixing, to form resulting log curves, the first and second log data sets, the extent of mixing varying from one logged depth to another in relation to a function of (a) the semblance between the recorded log data and reference log data of a differing kind from the recorded log data and (b) the activity of one of the said first and second log data sets at each logged depth; and (iii) displaying transmitting, saving, outputting or processing one or more resulting improved log curves.