As described in Chapter 6, the skeleton is divided into axial and appendicular portions (see Figures 6.1 and 7.1). The axial skeleton is structured from 80 bones segregated intothree major regions: the skull, vertebral column, and thoraciccage (Figure 7.1) . This part of the skeleton (1) forms the lon-gitudinal axis of the body, (2) supports the head, neck, and Chapter 7 The Skeleton 199 7 Figure 7.1 The human skeleton.
Above: Some cameras have a switch to set it to auto or manual focus. Manual focus, meanwhile, disables autofocus and enables you to adjust it yourself. This is useful when the focusing system can't find focus for whatever reason, such as when it's too dark or when there's little contrast in the scene.
AF-A is where the camera selects and goes between the last two modes. If it thinks the subject you are photographing is stationary, then it will automatically use AF-S focus mode. If it picks up that the subject you're photographing is a moving subject, then it will automatically use AF-C focus mode.his is also the default camera focus mode, unless you change the setting to AF-C or AF-S. MF is the manual focus mode. It's unclear why this focus mode is included, because nowadays there is usually an option to switch between auto and manual focus on the side of the actual lens.