Lookback Period

The number in an indicator's settings is usually its lookback: how many completed bars the calculation consumes to produce one value. A study with a long lookback needs that many bars before it can plot anything at all, which is why indicators start part-way along a fresh chart, and it cannot be plotted further back than the platform's stored history allows. The lookback is a choice and not a property of the market, so the same indicator on the same chart is effectively a different study at two settings. Because the period is counted in bars, it also interacts with the chart's time frame: the same number covers minutes on one chart and months on another. The obvious temptation is to search for the setting that would have worked best on the history in front of you, which produces a number fitted to that history rather than one that describes anything durable. That is not an argument for the published defaults either; it is an argument for recording where a setting came from, so a reading can later be judged against how it was chosen.