Continuous focus mode used for shooting digital photos of moving objects
It is harder to shoot good digital photos of moving objects than of still objects. When objects are still you have all the time that you need to focus on the object and set the other camera parameters like shutter speed and aperture. This time shortens as the objects in the frame move faster and faster.
An example of moving objects that you might be photographing is a runner in a race, a racecar in a racing event or a jet fighter in an air show. The closer you are to those moving objects the faster they appear to be moving relative to your position and the faster they move the less time you have to set the camera and shoot the digital photo. For example if you are really far from a racecar during a race you have more time to take the photo than if you are virtually on the track and the car is heading your way.
There are many aspects to shooting good moving objects photos. In this article we will only look at one: focusing on the object. Other parameters such as shutter speed and aperture are explained in other articles. When objects are in focus digital photos look sharp and crisp when objects are out of focus they look unclear and blurry.
With low-end pocket cameras you do not have much choice when it comes to focusing. The camera will make its best effort to focus on the objects and there is little control for you as the photographer to guarantee the results. Semi-professional photographer are more likely to use SLR digital cameras with zoon lenses when taking photos of moving objects in scenarios like those described above. When using such equipment you can take advantage of a focusing mode known as Continuous Focus.
In Continuous Focus mode the camera continuously focuses on the objects in the photo. Once the shutter button is pressed and as long as it is held half way down the camera continuously focuses on the objects in the photo. The camera continuously corrects the focus as the objects distance from the camera changes.
When using this mode to shoot photos of moving objects you should hold the shutter button half way down and continuously move the camera to follow the objects. The camera will continuously keep the objects in focus. When you are ready to shoot the photo simply press the shutter button all the way down. By continuously correcting the focus the camera guarantees that it is always ready to shoot the photo when you feel the composition is right. For example you can use this mode to track an airplane in an air show and take the photo exactly when the composition is right – maybe when another bigger and slower airplane is visible making the digital photo composition more impressive.
This mode is not free of drawbacks. One drawback is the associated high power consumption as the camera continuously corrects the focus it uses the power hungry motors in the lens in order to move the optical components back and forth. Another drawback is the need to keep the objects in focus in a specific area of the frame that the camera focuses on limiting the composition options - usually this area is in the center of the frame.
This article and more are from Danette Mckay who is an expert in his field. printing pictures provides more in depth information.