Canon PowerShot G12, Using Aperture Priority (Av) Mode to Isolate Your Subject

One of the benefits of working in Tv mode with fast shutter speeds is that, more often than not, you will be shooting with the largest aperture available. Shooting with a large aperture allows you to use faster shutter speeds, but it also narrows your depth of field.

To isolate your subject in order to focus your viewer’s attention on it, a larger aperture is required. The larger aperture reduces the foreground and background sharpness: The larger the aperture, the more blurred they will be.

The reason I bring this up here is that when you are shooting most sporting events, the idea is to isolate your main subject by having it in focus while the rest of the image has some amount of blur. This sharp focus draws your viewer right to the subject. Studies have shown that the eye is drawn to sharp areas before moving on to the blurry areas. Also, depending on what your subject matter is, there can be a tendency to get distracted by a busy background if everything in the photo is equally sharp. Without a narrow depth of field, it might be difficult for the viewer to establish exactly what the main subject is in your picture.

As we established in Chapter 4, Av mode is the key to controlling aperture and, in turn, depth of field. So how do you know when you should use Av mode as opposed to Tv mode? It’s not a simple answer, but your LCD screen can help you make this determination. The best scenario for using Av mode is a brightly lit scene where maximum apertures will still give you plenty of shutter speed to stop the action.

Let’s say that you are shooting a soccer game in the midday sun. If you have determined that you need something between 1/500 and 1/1250 of a second for stopping the action, you could set your camera to a high shutter speed in Tv mode and just start shooting. But you also want to be using an aperture of, say, f/4.5 to get that narrow depth of field. Here’s the problem: If you set your camera to Tv and select 1/1000 of a second as a nice compromise, you might get that desired f/stop—but you might not. As the meter is trained on your moving subject, the light levels could rise or fall, which might actually change that desired f-stop to something higher, like f/5.6 or even f/8. Now the depth of field is extended, and you will no longer get that nice isolation and separation that you wanted.

To rectify this, switch the camera to Av mode and select f/4.5 as your aperture. Now, as you begin shooting, the camera holds that aperture and makes exposure adjustments with the shutter speed (Figure 5.3). As I said before, this works well when you have lots of light—enough light so that you can have a high-enough shutter speed without introducing motion blur.

Several factors contribute to the appearance of this photo
Figure 5.3 Several factors contribute to the appearance of this photo: A high shutter speed catches the droplet just as it’s separating; a tight zoom frames the shot and helps to provide a shallow depth of field with the focus on the droplet’s stem; and a relatively wide aperture (the widest possible at that zoom level) enhances the depth of field and provides enough light that the photographer didn’t need to increase the ISO. [Photo: Dean Ducas]

Canon PowerShot G12, M: Manual Mode

Let’s face it—if you want to learn the effects of aperture and shutter speed on your photography, there is no better way to learn than by dialing in these settings yourself. However, today, with the advancement of camera technology, many new photographers never give this mode a second thought. That’s a shame, as not only is it an excellent way to learn your photography basics, but it’s also an essential tool to have in your photographic bag of tricks.

In Manual (M) mode, the camera meter gives you a reading of the scene. It’s your job to set both the f-stop (aperture) and the shutter speed to achieve a correct exposure. If you need a faster shutter speed, you will have to make the reciprocal change to your f-stop. This can be challenging at first, but after a while you will have a complete  understanding of how each change affects your exposure, which will, in turn, improve the way you use the other modes.

When to use Manual (M) mode

  • When learning how each exposure element interacts with the others (Figure 4.9)
  • When shooting silhouetted subjects, which requires overriding the camera’s meter readings (Figure 4.10)
  • When your environment is fooling your light meter and you need to maintain a certain exposure setting

Setting up and shooting in Manual mode

  1. Turn your camera on and turn the Mode dial to M.
  2. Select your ISO by rotating the ISO dial.
  3. Rotate the Front dial to choose a shutter speed, which appears at the bottom
    of the LCD. The exposure information is displayed by a scale with marks that run from –2 to +2 stops. A proper exposure (according to the camera meter) will line up with the arrow mark in the middle. As the indicator moves down, it is a sign that you will be underexposing (there is not enough light on the sensor to provide adequate exposure). If the indicator is above the middle mark, you will be providing more exposure than the camera meter calls for (overexposure).
  4. Rotate the Control dial to choose an aperture value, keeping the light meter in mind as you change the f-stop.
  5. Point the camera at your subject and then press the shutter button halfway to preview the exposure. As with the Tv and Av modes, the orange light by the viewfinder will blink if the image is underexposed or overexposed.
  6. Release the button and adjust the Front dial or Control dial to change the setting.
  7. Press the shutter button fully when you’re ready to shoot.

Beaches and snow are always a challenge for light meters. Instead of fighting the light meter, switch to Manual mode and dial in a good exposure yourself. [Photo: Michael Gerpe]
Figure 4.9 Beaches and snow are always a challenge for light meters. Instead of fighting the light meter, switch to Manual mode and dial in a good exposure yourself. [Photo: Michael Gerpe]
Although the meter can do a pretty good job of exposing for the sky, you can use the Manual mode to make creative adjustments, such as pushing the skyline elements into complete black silhouette. [Photo: Dean Ducas]
Figure 4.10 Although the meter can do a pretty good job of exposing for the sky, you can use the Manual mode to make creative adjustments, such as pushing the skyline elements into complete black silhouette. [Photo: Dean Ducas]