Photography Techniques

Auto Focus – Its type and various advantages and disadvantages

Auto Focus – Its type and various advantages and disadvantages
Written by Dave Peterson

Auto Focus – Its type and various advantages and disadvantages

Auto Focus – Its type and various advantages and disadvantagesAuto Focus – Its type and various advantages and disadvantages – The passive auto focus system is used by SLR cameras using interchangeable lenses. The active auto focus system is used in cameras not having interchangeable lenses. In certain high end cameras combination of both the systems is used. The selection of the right system is done by the camera as per the situation. Shooting blue skies will make camera to use active system while when distances are not infinite camera uses passive system.

Not always auto focus will equip your camera with the capability to have the best of the pictures. In the era when so much development have been done in the field of electronics and camera have lots of computing power auto focus in the camera fails. The reasons are many; few of them are listed here. Low light scenario will not allow passive auto focus system to work. Even though flash lights can be used to overcome such a situation but the solution is not a perfect one.

Auto Focus – Its type and various advantages and disadvantages

Auto Focus – Its type and various advantages and disadvantagesIn such a situation an active system will be ideal but again the results are not good if there are number of objects at various distances. Active systems may fail in the situation where objects have affinity to absorb infrared beam, in such situations the active system measures the wrong distance. With low contrast objects like blue skies or white walls, there is not a significant change in focus level hence passive auto focus fails. The better understanding of the situations where the camera cannot focus will lead the photographer to explore other solutions.

You can think of a possibility where you can easily focus on another object in the picture at the same distance as the main object that will serve the purpose of focusing the subject in the picture. The three main factors that influence auto focus are contrast of the subject to be photographed, level of light and motion of camera or subject. There is very little you can do to make the photograph look sharp if it was out of focus at the time of taking. The modern camera has three separate focus points which are placed side by side horizontally.

Auto Focus – Its type and various advantages and disadvantages

You don’t have to move the camera straight at the primary subject; instead if primary subject is to the left then left focus point will take care and for right side primary object right focus point will serve the purpose. Next very important thing to understand is the types of auto focus based on the procedure to be followed with the camera. There are two different types of auto-focus namely one shot and predictive auto focus. Most of the digital cameras work on one shot auto focus. In that you have to point the camera towards the subject with camera shutter halfway down.

Auto Focus – Its type and various advantages and disadvantagesThe camera will adjust itself to be in focus and lets you know the completion of adjustments with a beeping sound. For camera with multiple points the camera will light up the focal point selected. When you come to know about subject being in focus from the sound from camera, all you have to do is pull the shutter down completely and click the photo. Again the whole procedure is to be repeated for taking another shot. Another type of auto focus namely predictive auto focus is a standard feature of many DSLR cameras. In this mode of auto focus you don’t have to wait for camera to focus, moment you push the shutter camera determines the location of the subject and focuses accordingly. This is very helpful especially when subject is on the move.

Next part of the tutorials will explain in more detail one shot auto focus and servo multi point focus. How at times manual focus is better?

Tutorial Twenty Four –Manual Focusing – When is it better than Auto Focusing?

Tutorial Twenty Two –Auto Focus – All about active and passive auto focus

About the author

Dave Peterson

Dave Peterson
Passion for adventure and sharing his life long journey with as many others as possible.

"What lies behind us and what lies before us are tiny matters compared to what lies within us." HENRY S. HASKINS

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