f/X.X
The maximum aperture of the lens is denoted by the f-stop number, which is expressed as a fraction of the lens's focal length. It's possible that some zoom lenses will list both of their apertures, like f/5.6-f/4 for example. This indicates that as the lens is zoomed in, the maximum aperture of the lens will get increasingly smaller. The maximum aperture that may be achieved on the lens barrel can alternatively be described using a ratio, for example 1:4-5.6.
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