Home | Hobbies
Good focus of objects is a key element in producing a high quality digital photograph. You can achieve proper focus by two different methods, manual or automatic. We will concentrate on one method in particular that falls into the automatic focus category: combined auto focus. High quality sharp and crisp digital photos are a result of many optical parameters that need to be set right. One of the most important optical parameters is focus. When objects in a digital photo are out of focus they look blurry and are missing details and clarity. When objects are in focus they look sharp and crisp. While the photographer can manually set the focus, most of the time the digital camera's automatic focus is much faster and easier. There are many different methods and algorithms to automatically establish the right focus for the situation that a digital camera uses. Passive and active auto focus are two of these algorithms. These two algorithms in particular are used in one type of combined auto focus system to provide excellent automatic focus. Active auto focus systems use distance sensors measuring the distance from the camera to the objects in the scene. Typically the camera measures the distance to the object or objects at the center of the photo. Once determining that distance, the camera can then set the camera lenses to attain good focus. The ability to work in total darkness is one of the biggest advantages of active auto focus. This feature does have its challenges in unique situations. Active focus can fail to work when objects that emit certain energies (like infrared) are photographed or when surfaces in the scene absorb the energy used to measure the distance. Passive auto focus systems use software that runs on the digital camera built-in computer. The camera performs such image processing algorithms to establish a Focus Level number. This equation is much too complex to address here. Let's just say that the camera can calculate how good the focus is and find the best focus for the scenario. In some scenes the passive auto focus is limited or not serviceable at all. It does not work well in reduced lighting conditions and does not work at all in dark scenes. It is also hard to focus on low contrast objects such as walls or solid surfaces. Those cameras that are outfitted with combined auto focus systems have the ability to use the right system for the specific situation or cross check by using both systems at the same time. Of course, the photographer can also manually choose which option if they so desire. As an example, when shooting blue skies the camera can try to use the active system and calculate the distance. Since the distance is endless the camera can set the focus and skip the passive focus. In other cases when the distance is not endless the camera can use the active system to put the lens in about the right position and then use the passive system for fine tuning. In dark circumstances the camera can choose to use the active system given that the passive system will not work.
Article Source: http://www.content-corral.com
Did you enjoy this article? Interested in Dominating Digital Photography? Well now you can by Discovering this free Tutorial...what are you waiting for?
Please Rate this Article
5 out of 54 out of 53 out of 52 out of 51 out of 5
Not yet Rated
