All three of these advances would appear as the same vertical distance on a logarithmic scale. Most charting programs refer to the logarithmic scale as a semi-log scale, because the time axis is still displayed arithmetically. The chart above uses the 4th-Quarter performance of Verisign to illustrate the difference in scaling. On the semi-log scale, the distance between 50 and 100 is the same as the distance between 100 and 200. However, on the arithmetic scale, the distance between 100 and 200 is significantly greater than the distance between 50 and 100.
Arithmetic scales can be useful for short-term charts and trading.
Trendlines tend to match lows better on semi-log scales. Large movements are put into perspective. With this in mind, it also makes sense to analyze price movements in percentage terms. Conclusions Even though many different charting techniques are available, one method is not necessarily better than the other. The data may be the same, but each method will provide its own unique interpretation, with its own benefits and drawbacks.