Logarithmic and Linear Price Scales

A chart's vertical axis can be spaced two ways. On a linear scale, equal vertical distance means an equal amount of price movement, so the same number of pips occupies the same height anywhere on the chart. On a logarithmic scale, equal vertical distance means an equal percentage change, so a move is drawn according to its size relative to the level it started from. The prices plotted are identical; only the spacing between them differs. The choice changes the shape of anything drawn by hand. A trendline connecting the same two points is a different line on each scale, so a break of it can be present on one and absent on the other, and the same holds for channels, wedges and any figure whose boundaries are drawn rather than calculated. The difference is negligible across a narrow price range and grows with the range covered, which is why it shows up most on long histories. Neither scale is more correct than the other; what matters is knowing which one a chart is using before comparing a drawing on it with someone else's.