Girl Group Portait Photography

Lenses
Lenses used in portrait photography are classically fast, medium telephoto lenses, though any lens may be used, depending on artistic purposes. The first dedicated portrait lens was the Petzval lens developed in 1840 by Joseph Petzval. It had a relatively narrow field of view of 30 degrees, a focal length of 150mm, and a fast f-number in the f/3.3-3.7 range.
Classic focal length is in the range 80–135mm on 135 film format and about 150-400mm on large format, which historically is first in photography. Such a field of view provides a flattering perspective distortion when the subject is framed to include their head and shoulders. Wider angle lenses (shorter focal length) require that the portrait be taken from closer (for an equivalent field size), and the resulting perspective distortion yields a relatively larger nose and smaller ears, which is considered unflattering and imp-like. Wide-angle lenses – or even fisheye lenses – may be used for artistic effect, especially to produce a grotesque image. Conversely, longer focal lengths yield greater flattening because they are used from further away. This makes communication difficult and reduces rapport. They may be used, however, particularly in fashion photography, but longer lengths require a loudspeaker or walkie-talkie to communicate with the model or assistants. In this range, the difference in perspective distortion between 85mm and 135mm is rather subtle.
Speed-wise, fast lenses (wide aperture) are preferred, as these allow shallow depth of field (blurring the background), which helps isolate the subject from the background and focus attention on them. This is particularly useful in the field, where one does not have a back drop behind the subject, and the background may be distracting. The details of bokeh in the resulting blur are accordingly also a consideration; some lenses, in particular the "DC" (Defocus Control) types by Nikon, are designed to give the photographer control over this aspect, by providing an additional ring acting only on the quality of the bokeh, without influencing the foreground (hence, these are not soft-focus lenses). However, extremely wide apertures are less frequently used, because they have a very shallow depth of field and thus the subject's face will not be completely in focus. Thus, f/1.8 or f/2 is usually the maximum aperture used; f/1.2 or f/1.4 may be used, but the resulting defocus may be considered a special effect – the eyes will be sharp, but the ears and nose will be soft.