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BY ANDREA GHILARDELLI

Depth of field is the major element to consider when choosing the best aperture for group portraits. Usually, sharp focusing in group portraits is challenging because it is not trivial to pose all the individuals in the same zone of focus. Hence, a strong limitation to the available apertures is the necessity to set the lens aperture so that its depth of focus is enough to accommodate everyone in the group within the depth of focus. This is particularly true for big groups. Therefore, considerations and concerns about depth of field have precedence over all other aspects.

There are other considerations, however. From an optical point of view, for instance, a lens used with a wide aperture is afflicted by spherical aberration, whereas if used at small aperture it is afflicted by diffraction. So, some good advice: never use a lens at its maximum or minimum aperture.

Moreover, due to optical considerations, a lens yields its optimum performance when used at a couple of f-stops narrower than its maximum aperture. So, use this setting whenever possible.

Determining the correct shutter speed is a less complex problem. Sure enough, the shutter speed must be fast enough to freeze any movement, both of the camera and of the subjects. In particular, when shooting outdoors, watch out for hair movement caused by the breeze, so set the shutter speed accordingly.

Always keep in mind that the closer you are to your subject, the higher the shutter speed you should use, because the subject’s apparent motion will appear swifter. The same holds true in general for highly magnified or zoomed in subjects.

There is a rule of thumb stating that the shutter speed should not be lower than the reciprocal of the focal length. For instance, if using a standard 50mm lens, a shutter faster than 1/50 should be used. The fulfillment of this rule will assure motionless pictures. Of course, slower speeds are achievable with a tripod.

A very refined technique consists of “dragging” the shutter. This means setting a shutter speed lower than necessary when using a flash. This technique is used to correctly expose both the main subject and the background. Select the shutter speed and the aperture to ensure a correct exposure of the background with just the ambient light, and then set the flash power for correctly exposing the main subject with the set aperture.

Andrea Ghiladelli runs the Ilghila Online Photo Retouching Service.