I hear people talking about groups and elements in lenses, but I am not sure what they mean. Could someone please explain?
Answer
Except for a few budget cameras of the past, all camera lenses are made using at least two or more separate lenses. Each of these “thin” lenses is termed an “element”. In optical jargon, when individual lens elements are combined, the pair is called a “component”. Thus the typical camera lens contains several components. The elements that make up a component are usually, but not always, cemented together. Several components make up the compound camera lens. Components are generally not in contact with each other. Between them is an “air-space”. The air-space is also lens shaped, and thus it acts as a weak lens. The synonym for component is "group".
Such a complex mix of elements and components are needed to mitigate defects that prevent the lens from making a faithful image. We are talking about aberrations. There are seven aberrations, two induce color errors, five induce blur and/or distortions.
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