Back to the Basics Part I: Exposure

Back to the Basics Part I Exposure

Hey! Shutter Science has been writing a Camera Basics tutorial series which will start this week! We will cover the topic of exposure and how it relates to modern digital cameras. Alot of cameras come with auto functions that take care of exposure for you, while it works it does not provide you with the highest quality pictures. Understanding how exposure and how to manually control it, will provide you with a new skill set to bring to the table when you are shooting.

What you will need:

• A DSLR or point-and-shoot digital camera with Manual function.
• Thats it this time!

How it works

When you use your camera to take a photograph, you are exposing a digital imaging sensor to light. Before the light hits the center, there are two ways of controlling how much light is picked up by the sensor. These controls are called the Aperture and the Shutter. The latter of which this blog is named for. In order to manipulate these controls you must have a camera with manual mode.

Aperture

The aperture in your camera is a mechanical opening that changes in size to admit more or less light into the lens/camera body. The sizes it can open and shrink to are setup in measured increments and are known as F-Stops. The numbers step up from F1.4 to F5.6, F8, and F11. As the F-stops number increase in value, the smaller the opening of the aperture, and consequently the less light allowed into the camera. It is important to note that with each increase in F-stops means half as much light will be let in.

Shutter 

The shutter is a mechanical blind for the imaging sensor. It opens and closes at an again incremented and predetermined speed allowing only light to reach the sensor for so long. Shutter speeds are measured by fractions of a second, 50 means 1/50 or one fiftieth of a second, and 125 means 1/125. There are also speeds longer than a second or less, which we will touch on later.

How long you leave the shutter open for can vary depending on the situation or the scene and how bright it is. A sunny day may require a shutter speed of 1/200 and an aperture of F8, while a overcast, or cloudy day could be 1/60 with a F-stop of F4

Leaving your shutter open for different lengths of time when properly exposed by balancing out the apertures setting (ie if it is really slow such as if you are shooting a long exposure), can produce different effects in your photographs, especially where motion is concerned. A few photographs will follow to detail this.

Fast shutter speeds will freeze motion in a very clear way as opposed to the blurred effect that a long exposure creates. As you can see in this photo the high shutter speed freezes the water cascading off the rocks into individual rivulets of water. It is worth noting that any shutter speeds under 1/60 or even 1/80 for that matter are too slow to be taken while holding your camera, this will add a type of motion blur called shake to your photo. Camera shake comes from your body's inability to hold the camera perfectly still for that time period, this is okay though, thats why we have tripods.

Slow shutter speeds capture motion very differently, and any object or scene in motion on a long exposure will leave trails of motion blur as the objects travel across the scene. As you can see in the photo above, the water is smoothed out in this scene as it runs off the rocks and takes on a gassy smokey look.