Canon Digital Rebel XSi There is no photo more elusive and more difficult to capture than the perfect action shot. Getting a clear picture of the game-winning touchdown, a crucial stolen base or even your kids playing in the front yard can be extremely frustrating. A bit of streaking or blurring can spoil what could have been a cherished memory. Avoiding such pitfalls requires you be smart about how to properly use your digital camera — and a bit of luck. With the right equipment and information, you'll be ready to immortalize that decisive moment in a photograph.

Pro sports photographers use high-end digital cameras like the Nikon D2X ($5,100 US) or the Canon EOS 5D ($2,499), which are finely tuned to produce newspaper or even magazine-class photographs. That's overkill for most consumers. Manually configurable cameras, such as the mid-range Fuji FinePix S1000fd ($249.95) or Sony Cybershot DSC-H9 ($399) and excellent digital SLRs like the Canon Digital Rebel XSi ($799), will churn out quite decent photos for weekend photographers.

Being able to manually access the camera's settings is absolutely necessary if you want to be able to maximize the potential for taking an excellent sports or action photo. This is why it's better to have a mid-range advanced or extended zoom camera or a higher-end digital single lens reflex (SLR) camera. In the interest of affordability and ease of use, point-and-shoot and ultracompact cameras typically do not allow for full manual control of shutter speed and aperture. Instead, they rely entirely on the automatic "sports mode," which will do in a pinch, but doesn't allow for the fine adjustments that could make a good photograph great.

Most contemporary digital cameras feature a "sports mode," which automatically adjusts the camera's settings to compensate for fast-motion scenarios that look like a blur if you shoot in standard, automatic mode. Sports modes are a shortcut, providing a straightforward, simple way to configure the three advanced settings that must be tamed to fine-tune your action photography: Shutter speed, aperture and light sensitivity. While sports mode is a fine start for most people, understanding how these three elements affect a photo and how they can be used effectively are the keys to excellent action photography.

Shutter speed

The shutter speed refers to how long the hole through which light enters the camera (the aperture) is left open. If the aperture is left open for a long period of time (in this context, only a few seconds) the camera will capture everything that transpires and write it to a single photograph. Taking a photograph of a fast sprinter or a speeding car while using a slow shutter speed will result in motion blur — the streaks that trail behind fast-moving objects. Essentially, the subject of the photo changed position so quickly that the camera saw it moving across the frame.

Sony's Cyber-Shot DSC-H9. You can mitigate motion blur distortions by using a faster shutter speed — effectively opening and closing the aperture more quickly. That way, your photograph captures only a split-second moment, not a series of moments smeared together. Shutter speed is measured in fractions of a second. You want the tiniest fraction possible — say, 1/500 instead of 1/60. The different speeds are called "stops." Each stop on the setting cuts that speed down by about half.

The artistic quality of your picture can get penalized a bit as you increase the shutter speed to catch that action shot: If you increase the shutter speed too much, you risk robbing the photograph of its intensity by freezing it in time. That means to get the most compelling sport pictures, you need to fiddle with your camera to find the right balance of clarity with a quick shutter speed.

Aperture

Then there's the aperature setting. The aperture is the hole through which light enters the camera. Advanced cameras let you manually control the size of the aperture, giving you another way to determine how much light your camera soaks up.

The primary effect of changing the aperture settings is seen in your photograph's depth of field. A smaller aperture which lets in less light results in a large depth of field — meaning that the entire photograph (everything in the foreground and background) will appear in focus.

Conversely, a larger aperture, which lets in more light, creates a small depth of field. This tightens the focus on the foreground and casts the background of the image in an indeterminate blur. Aperture settings are called "f-stops," with higher numbers referring to smaller aperture sizes (f/16) and lower numbers referring to larger apertures (f/4).

This is another situation where a photographer's artistic sensibilities must come into play. A large depth of field would be excellent for capturing a sports scene where many players are scattered across a field. A short depth of field is useful when you zoom in a particular player or point on the field.

ISO settings

The final element worth considering is light sensitivity, more commonly described as a camera's ISO settings. The higher the number (most cameras top out at ISO 3,200 or 6,400), the better a camera performs in low-light situations.

Nikon's D60. Essentially, higher ISO settings allow photographers to do more with less light. For example, if you were to use a slow shutter speed or small aperture, both of which reduce the amount of light entering the camera, using a higher ISO setting would help compensate. The only downside is that this often results in increased image noise, grainy, speckled distortions that reduce the clarity of the photo. It's not perfect, but making ISO adjustments can be especially helpful when shooting indoors and outside at dusk or evening.

If total manual control still seems scary, some cameras have intermediate modes like Shutter-Priority and Aperture-Priority. These allow you to make a custom adjustment to the indicated setting while allowing the camera to automatically adjust the others to best complement your choice. They can be found on dSLRs like the Digital Rebel XSi or Nikon's superlative, lightweight D60 ($749.95) as well as more affordable models like the Nikon P80 ($399.95).

Don't be a passive photographer. If you want to capture scenes with great action and intensity, start by getting better acquainted with your digital camera and all its settings. You'll quickly see dramatic results that will bring those adrenaline-fueled moments home without losing any of their impact.

Michael Patrick Brady is editor of DigitalCamera-HQ.com. It operates product commentaries and answers questions on a range of consumer electronics, including digital cameras, camcorders and high-definition televisions.