Each lens has a minimum distance from which it can shoot a subject. This distance is called minimum focusing distance. If you get closer to the subject than this distance, you cannot focus on the subject properly.
The minimum focusing distance varies by lens; in zoom lenses, it can also vary depending on focal lengths. To check the minimum focusing distance of a lens, refer to the lens specifications or the distance printed on the lens, as shown in the picture below.
The distance is indicated on the front side of the lens in meters (m) and feet (ft). The minimum focusing distance of the SELP1650 lens above is from 0.25 m (25 cm) to 0.30 m (30 cm), depending on focal lengths. If you get closer to the subject than this distance, you cannot focus on the subject properly, and the shutter cannot be released.
In situations where you want to get as close as possible to the subject (for instance, when taking close-ups of flowers), first get extremely close to the subject. Then move away little by little to find the distance where the subject is in focus.