— when shooting portraits, firstly, a good aperture ratio is necessary, and secondly, a relatively large focal length (more than 50 mm in the equivalent of 35 mm). The first feature is necessary to create a beautiful background blur, the second makes it easier to organize the space in the studio, allowing you to place the camera behind the lighting fixtures (otherwise it could create a shadow). But a variable focal length for such shooting is usually not required, so most of the "portraits" are fixed (see "Focal length").
