In This Chapter
Understanding depth of field
Rules of composition
This chapter contains some concepts that may be well-known to some D90 users, while other users may need a refresher. Some of this information may be brand-new to those of you who are just stepping into the world of dSLR photography. If you're an advanced user, you may want to skip this chapter, although you may discover some new information or something you may have forgotten. This chapter covers information on exposure, the effects aperture has on depth of field, and some tips and hints on composition and lighting.
An exposure is made of three elements that are all interrelated. Each depends on the others to create a good exposure. If one of the elements changes, the others must increase or decrease proportionally. The following are the elements you need to consider:
Shutter speed. The shutter speed determines the length of time the sensor is exposed to light.
ISO sensitivity. The ISO setting you choose influences your camera's sensitivity to light.
Aperture/f-stop. How much light reaches the sensor of your camera is controlled by the aperture, or f-stop. Each camera has an adjustable opening on the lens. As you change the aperture (the opening), you allow more or less light to reach the sensor.
Figure 5.1. For this image, I exposed ...