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Archive for September, 2010

While attending the New England Regional Championships, an interesting question came up among several experienced Schutzhund photographers: Which is best when photographing Schutzhund dogs in action: Aperture Priority or Shutter Priority? To answer that question requires reviewing the purpose of each of these shooting modes and understanding that achieving proper exposure and focus is not just a choice between the two, but is actually a three-way relationship between the aperture setting, shutter speed and the ISO setting.

Aperture Priority is designed to allow photographers to manually control the aperture while the camera automatically adjusts the shutter speed to get the correct exposure. This mode is useful for blurring the background by setting a wide (large) aperture (low f-stop number) and zooming in on the subject. This is particularly advantageous to mute a cluttered background and to highlight the photo’s subject, as it is the only thing in focus. This mode can be tricky when shooting fast action, as the camera may choose a lower shutter speed than is needed to achieve sharp focus and effectively stop the action. As a result, the exposure may be correct, but the photo may be out of focus.

Jerry Welch in his article Aperture Priority vs Shutter Priority explains: The lens aperture setting (f-stop setting) determines the depth of field. Depth of field settings determine how much of the foreground and how much of the background is in focus. The larger the aperture, the smaller the f-stop number, the shallower the depth of field. The smaller the aperture, the larger the f-stop number, the deeper the depth of field. The smaller the aperture the more of the foreground and background will be in sharp focus.

As a rule of thumb: When the subject is bright, use a smaller aperture setting (larger numbers: f/8, f/11, f/16, f/22). When the light on the subject is dim, use a larger aperture (smaller numbers: f/5.6, f/4, f/2.8). For Schutzhund photography, it is best to use “fast” lenses, with larger apertures.

To determine the actual depth of field for your lens at any given f-stop, check out this online calculator: www.dofmaster.com/dofjs.html. Select your camera model, lens focal length, f-stop, and the distance to your subject and the calculator will tell you the foreground limits and the background limits for sharp focus. There are also iPhone, iPad, Palm OS and Windows applications available from this website and some additional explanations about calculating depth of field.

Shutter Priority is designed to allow photographers to manually control the shutter speed, while the camera automatically adjusts the aperture to get the correct exposure. Using the Shutter Priority mode, photographers can stop the action without blurring the subject, foreground or background. By shooting at a slower shutter speed, photographers can add blur to the moving subject to show movement while keeping the background and foreground in perfect focus. Another technique is to use a slower shutter speed and then pan the camera to keep the subject perfectly focused while adding blur to the background and foreground. The downside of shooting in Shutter Priority mode is the faster the shutter speed the less light is allowed into the camera, which can adversely affect exposure.

In his article “Understanding the Relationship Among Aperture, Shutter Speed, and ISO”, Alton Vance explains: Shutter speeds are also referred to in the scale of stops. Every time you double the speed you step down by one stop: From 1/100 to 1/200 is a one stop down in the amount of exposure, 1/200 to 1/400 is one more stop down and so on. The faster the shutter speed the more accurately the action can be frozen, but it lets in only half as much light with each stop down. For normal everyday photography use a shutter speed of about 1/250th of a second. If the shutter stays open for 1/100th of a second then more than twice as much light comes in. If the shutter stays open for 1/500th of a second only half as much light come in. Shutter speeds can be as fast as 1/8000th of a second.

Aperture and shutter speed are only two parts of the exposure relationship. The ISO setting is also very important and is useful when shooting in either Aperture Priority or Shutter Priority modes.

Alton Vance explains: The ISO setting refers to the sensitivity of the image sensor to light. Some digital cameras have ISO settings that range from 50 to 3200. That is a range of six (6) stops in the exposure category. Every time the ISO rating is doubled, essentially one full stop of exposure is added. For example, 50 to 100 is one full stop of exposure, 100 to 200 is one full stop, 200 to 400 is one full stop, 400 to 800 is one full stop and so on. Higher ISO settings tend to create more grain or noise in the image. As a result, ISO-100 will have much a smoother finish than ISO-800. So the rule of thumb is to use as low ISO setting as possible and still have enough light to obtain a proper exposure.

In my experience, Shutter Priority provides the most reliable photos of Schutzhund dogs at work. It allows me to freeze the action and not worry about adjusting the aperture to accommodate different lighting conditions. Anyone who has tried photographing Schutzhund dogs over several hours knows that lighting can change dramatically, depending on the whims of the weather and there often isn’t time to stop, reset the camera settings and capture the action. I start with a shutter speed setting of 640 and adjust the ISO as needed. In the end, it’s a judgment call, one that is made easier by understanding the relationship between aperture, shutter speed and ISO and also by experience and experimenting.

Note:  Next up – back to the Composing Schutzhund Photos series.

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