How to adjust the metering mode and focusing mode of Nikon D90?

There are two buttons behind the shutter button on the right, and the metering button on the left. Press and hold, dial the main wheel (near the right thumb) to adjust the metering mode, and set the fn function key to adjust the focusing mode.

1. autofocus mode:

1.AF-S mode is used to shoot still objects, such as still life and scenery. In this mode, the camera focuses on the data at one time. After the object moves, the camera will not focus continuously unless you press the shutter again.

2.AF-A mode is to automatically select AF-C and AF-S modes. When focusing on static objects, it automatically defaults to AF-S mode, and when focusing on dynamic objects, it automatically defaults to AF-C mode, so this mode is more common and convenient. A is depth mode, that is, the shutter is always pressed. When the distance between the focused object and the plane position changes, it will automatically continue to focus until it is refocused. (For objects moving along the lens axis)

3.AF-C mode is used to shoot and focus dynamic objects. When the object moves, the camera will automatically zoom in real time in this mode. If an object leaves the focus, it can't focus. For example, if you follow the car running on the road, after you focus, the focus can move with the car, the camera will focus automatically continuously, and you can get a clear picture of the car with a dynamic blurred background by pressing the shutter. C is omni-directional mode, that is, when the shutter is pressed for half a time, it will refocus when the focused object moves or the camera moves. (For objects moving laterally or irregularly)

Second, the measurement mode:

When the camera is shooting in M mode, first set the aperture, then set the shutter speed, and then look at the exposure value in the viewfinder. Be sure to understand the principle of white plus black minus. When exposure value is in the middle position, you can shoot. This is the best combination of aperture and shutter speed.