Would you like to take wildlife pictures like you see in magazines, or even turn everyday objects into photographic art?
Did you ever see an image where only a small part of it is sharp? Using the aperture ring correctly can maximise the artistic look of your image.
Not only does it determine the depth-of-field, it also has the power to direct the human eye.
The human eye is instinctively drawn towards noticeable points of an image. These are usually the sharpest and most important parts of an image. Using a wide aperture to limit the area of sharp focus can direct attention to the most important elements of your image and blur out any off-putting backgrounds.
This isn’t that hard to accomplish, and can be blissful if done correctly.
Lets start off with understanding depth-of-field, aperture and f/stops.
Depth-of -field: The distance from the front to back that is in reasonable sharp focus is called the depth-of-field. There are two ways of controlling depth-of-field: Use a small aperture or focus on a point farther away from your camera.
Aperture and f/stops: The aperture is an opening in the centre of the lens through which light passes. The amount of light, which passes through an aperture, is indicated by f/stops. The lower the f/stop the more light that passes through the aperture. Opening up one full f/stop doubles the amount of light entering the camera. F/4 admits twice the light of f5.6.
By selecting a small or narrow aperture (f/16 or up), all or most of the scene will be reasonably sharp. This is ideal for landscape photography. By using a small aperture you increase the depth-of-field.
By selecting a large or wide aperture (f/5.6 or below) you decide which part of your image is sharp. This is ideal for taking pictures of wildlife, portraits, sport and small objects. By using a large aperture you decrease the depth-of-field
The smaller the f/number, the wider the aperture.
There is about twice the depth-of-field behind the point of focus as there is in front of it, using any aperture.
Now you know how to isolate your subject, so it’s time to put it to use. Set your camera to aperture-priority (AV) mode, and then select a large aperture (f/2 - f/5.6). By doing this the camera will select the shutter speed automatically. If you are shooting wildlife choose a low viewpoint to maximise the image, try putting the camera lens at eye-level with the subject.
While the above will help to isolate you subject, it’s only a start. Know your subject, especially when shooting wildlife. Don’t be fooled into thinking all elements of an image must be sharp to be considered a good photo.
The shutter is a mechanical device that controls the length of time that light is allowed to act on the film. Most standard cameras allow us to use a range between 16 second and 1/1000 second. You might be wondering, why anyone would use a long shutter time of 16 seconds: I’ve used this and even longer shutter times when taken lowlight landscape images. I would always advise the use of a tripod with these long exposures time to avoid blur images.
Using a shutter speed of 1/125 second should safely avoid overall blur due to camera movement if you hold the camera by hand. Any longer shutter time should require a tripod.
Each time you open the shutter by one, we double the light, when we close down the light by one we half the light. Open the shutter at 1 second allows twice the light as that of a ½ second.
The shutter can also be used creatively when taking landscape images or sport images. If you want to add motion to your image a slow shutter speed can give an image an extra bit of sway. No more so than taking images of streams. Using a slow shutter speed when photographing water will cause the water to blur, resulting with the image expressing motion.
By contrast, a fast shutter speed of 1/250 would be used in shooting wildlife or where the subject that you’re shooting needs to be still and sharp. Most wildlife photographers would use a fast shutter speed.
By using the shutter and aperture together we control exposure. Both allow light to enter the camera: the shutter by time and the aperture by the size of the hole in the lens.
For example: you’re shooting a landscape scene; you get an exposure reading at f/11 at ¼ second. You know that by using f/11 that the entire image wont be sharp. You want to shoot at f/22, which is four times less light than f/11. You need to quadruple the light through time; each time you open the shutter by one you double the light, so open it by two stops and your exposure time will be 1 second. Your final exposure should read f/22 at 1 second.
At the best of times, calculating the correct exposure can be a difficult task, but with a few simple tips our images can produce eye-catching colours that we see all around us every day.
TJ Tierney. Irish landscape photographer. http://www.goldprints.com
