There are three things that we can control that affect how a photo is exposed:
- Shutter speed
Shutter speed is how long the lens is open. Aperture is how wide it’s open. ISO is how sensitive the camera is to recording light.
If we leave the shutter open for a long time, a lot of light gets in. This is called a slow shutter speed. If the shutter is only open for a very brief moment, less light gets in and this is called a fast shutter speed. A fast shutter speed is useful for when we want to freeze motion and get a very crisp image, and a slower one is useful for capturing motion blur.
Fast shutter speeds are also useful for avoiding blur from the photographer’s shaky hands.
Your camera has a meter that measures light and uses that measurement to decide what exposure is best for a given situation. In fully automatic mode, the camera picks out both the shutter speed and the aperture. In aperture priority mode, you set the aperture and the camera picks the best shutter speed. In shutter priority mode, you pick the shutter speed and the camera picks the best aperture. You can also put the camera into fully manual mode so that you can choose your own aperture and shutter speed, and the camera’s meter will just offer advice.
If you’ve been following along and doing the exercises, you’ve also learned how to put your camera into different modes and what images look like at various shutter speeds.
Next up: the magic of aperture and how it can dramatically change our photos.
Next lesson: What’s that f-stop stuff anyway?