The selective focus technique requires a large aperture?
A.: Yes, this is one of the reasons pros prefer wide aperture lenses. However, the use of a large aperture is not always straightforward. A larger aperture (a smaller f number for the same focal length) requires a faster shutter speed. If a flash fill is used, the maximum shutter speed is limited by 1/250 s or lower, depending on the SLR camera. The photographer on a bright day has two options: to use a slow film or a neutral density filter. A polarizer helps as well to slow the shutter speed. The A mode (aperture preferred) allows to select a large aperture but when the flash is turned on, most cameras reduce the shutter speed to the synch speed and a gross overexposure may result. When photographing people outdoors with fill flash I use the shutter preferred S mode at 1/250 s to get the narrowest depth of field possible.
