A log scale is best for...

Long histories with big % moves

Line, bar and candle charts

The same prices can be drawn in different ways. A line chart joins the closing prices: clean and simple, perfect for the big picture and comparing markets.
A bar chart (OHLC) shows open, high, low and close with a vertical line and two small ticks: left tick = open, right tick = close.
A candlestick chart shows the same four prices with a coloured body. Most traders use it because who won each period jumps out at a glance.
Long histories need care. Gold went from about US$38 in 1971 to over US$4,000 in 2025. On a normal scale, its rise to over US$600 by 1980, more than 15 times, looks like a tiny bump.
A log scale fixes that: equal % moves look equal. A move from 10 to 20 looks as big as one from 100 to 200, because both are +100%.
Common mistake
Mistake: comparing two charts without checking the scale and the dates. The same data can look calm or dramatic depending on how it's drawn.
Key takeaway
Line for the big picture, candles for detail, log scale for long histories.

A line chart usually connects... Closing pricesOne price per period, normally the close, joined into a line.
Which chart shows open, high, low and close with coloured bodies? CandlestickThe body colour shows at a glance whether price closed up or down.
A log scale is best for... Long histories with big % movesIt shows percentage moves fairly, so early decades don't look flat.
On a log scale, which two moves look the same size? 10 to 20 and 100 to 200Both are +100%, and a log scale draws equal % moves the same size.