Article by Walt Polley – Guest contributor
Photography is all about light
With no light, there would only be darkness. By controlling light in the camera, we are able to control shadows, bring out colors and shapes, and define shapes and dimensionality. Slight changes in how the light is treated can result in different final images. Three important settings to control light are Aperture, Shutter Speed, and ISO. These three settings are used control how light is let into your camera when you create a photographic image.
Aperture – The Light Hole – Controls Depth of Field
The aperture of our camera is a device that opens and closes, similar to the iris in someone’s eye. It is a tiny hole that controls how much light comes into the camera. The larger the hole, the more light comes through. This hole – called aperture – is measured in f-stops where f/4 is a large opening and f/16 is a small opening.
Changing aperture size changes your image’s depth of field. The depth of field is the range of distance where your image is acceptably sharp and in focus. A large aperture creates a shallow depth of field, and only a small range of your image is sharply in focus. A small aperture creates a deeper depth of field with details remaining sharp from foreground to background.
Using Aperture Priority mode (A or Av) on your camera will let you select and adjust the aperture size manually. The camera will automatically change other settings to ensure your photo comes out properly exposed. By experimenting with various aperture sizes and seeing the results, you will see how different apertures influence your depth of field.
Shutter Speed – The Timer – Controls Motion
While aperture controls the size of the hole that light enters from, the shutter speed controls how long the light is let in, measured in fractions of a second. A short shutter speed of 1/500 second will let in very little light to your camera’s sensor, while a longer shutter speed of 1/4 second will let in much more light. Using your camera’s shutter priority mode (S or Tv) will show you how shutter speed affects the images that you take. You will find that fast shutter speeds freeze motion while slower shutters blur motion.
Note: When using a slow shutter speed, be sure to use a tripod or other stabilizing device. Because light is let in for such a long time, any movement of your camera will BLUR and ruin your image.
ISO – Your Camera’s Sensitivity to Light
The ISO controls the sensitivity of your sensor to light. Basically, this lets you control how your camera reacts to the light let in from the aperture and shutter. Select a high ISO (very sensitive) and your camera can “see” in dim light. Select a low ISO and your camera won’t require sunglasses even on a bright sunny day at noon on the beach.
A higher ISO number will make your image expose faster and require less light than a lower ISO. The drawback of using a larger ISO is that the higher ISO often results in a reduction of image quality and increased noise or graininess of the image.
With three settings to juggle, each producing different effects, how do you manage all three?
When the depth of field is a top priority for your images, select Aperture Priority (A or Av) on the selector dial. Selecting aperture priority allows you to choose the aperture while your camera figures everything else out. If you want a shallow depth of field, use a large aperture of f/2.8 to f/5.6. If you have an expansive landscape shot and want lots of depth, use a smaller aperture of f/11 or f/16.
Shutter Priority (S or Tv) on the selector dial is used to freeze action and prevent blur or to deliberately cause blur. For example, when you are trying to capture a fast-moving bird or sports star, shutter priority will allow you to focus on what matters most – stopping motion. You would select a shutter speed of 1/500 second, and your camera figures out the rest. Or if you find a waterfall and want to create an ethereal blur-effect of the moving water, select a slow shutter of 1/4 second or longer. Don’t forget to use a tripod with longer shutter speeds.
Adjust the ISO based on the available light. You might use a low ISO (64 to 200) at a sunny beach, outdoors in bright sun, or during a studio photo shoot. When there is less light, you might choose a higher ISO (400 to 1600) in the late afternoon, inside a building with low-moderate light, or at night.